Life On An Oxfordshire Lawn

Two Noctuidae Moths - The Square Spot Rustic and The Setaceous Hebrew Character

2011-10-10T22:52:00.002+01:00

I am an amateur naturalist trying to discover everything living in my garden.

Some time ago I blogged (here and here for example) my homebuilt mothtrap. I set the trap out in my garden only a few times during 2009 and 2010. So great was the catch however that I'm still working through a backlog of photos of the species I caught (all critters were released alive after being photographed incidentally).

Two species from August 2009 I'm tolerably confident to have identified correctly (with the help of my copy of the Concise Guide to the Moths of GB and Ireland, by Townsend, Waring and Lewington) are a Square Spot Rustic (Xestia xanthographa) in photo 1 and a Setaceous Hebrew Character (Xestia c-nigrum) in photo 2.

The curious Latin species name 'c-nigrum' makes sense when you know nigrum means 'black in colour', hence literally 'with a black letter ''c''' [on its wings]. (Some of you may remember the 'white letter c' butterfly P. c-album I blogged here.)

I've entirely failed to uncover the meaning of the genus name Xestia. Can anyone comment?

Turning to the English common names of moths, I learnt previously that many were invented in the 1730's by the Aurelain society of naturalists. I'd guess (but don't know) those of the moths here were amongst them.

I needed to look up setaceous. It means whiskery incidentally.

From the book mentioned above I learn that both my moths are common in the UK. Both overwinter as caterpillars. The caterpillars of the Square Spot Rustic commonly dine on grasses, and those of the Setaceous Hebrew Character on nettles and other herbaceous plants.

My attempt to learn a little more about my moths led me to some interesting papers by Chapman et.al. [1] and Wood et.al. [2] and The papers describe the authors' efforts to track the migration of insects using ground-based radar. The papers are full of amazing details: I had not hitherto imagined that ground based radar would be so sensitive as to allow tracking of a single grasshopper in flight at a height of 1.5km. Further, as the authors explain, that around the globe millions of tons of insects are aloft at any instant, or that at least 2.3 billion(!) insects were involved in the migrations to/from the UK between 2002 and 2007.

What it is the insects (many moths, including mine, amongst them) are doing at heights of several hundred metres to a few kilometres is taking advantage of high wind speeds to propel them to places of seasonal migration. The speeds are several times greater than that at which an insect could fly unaided. The authors' studies yielded estimates that by harnessing winds insects may be able to travel as far as ~2000km during only three of four 8-hour flights. Things are not as simple as the insects being mere passive 'leaves in a storm' however. Rather, the authors discovered that they exhibit a clear directional sense, flying at an angle to the main wind direction so as to control where they end up. (I suppose an analogy would be a rowing boat in a strong ocean current. Just because the current may be faster than you could row, by sculling at an angle to the main current it's still possible to steer somewhat). How the insects are able to navigate at altitude and at night the papers don't say. I guess the moon may be involved, but that much about how they do so remains a mystery.

References
1. Flight orientation behaviors promote optimal migration trajectories in high flying insects, J.W. Chapman, R.L. Nesbit, L.E. Burgin, D.R. Reynolds, A.D. Smith, D. R. Middleton, J.K. Hill, Science 2010, 327, p.682-685

2. Flight periodicity and the vertical distribution of high altitude moth migration over southern Britain C.R. Wood, D.R. Reynolds, P.M. Wells, J.F. Barlow, I.P. Woidwod, J.W. Chapman, Bulletin of Entomological Research 99(05), p.525-535, 2009

Cat's Ear Hypochaeris radicata

2011-10-08T14:46:00.001+01:00

I am an amateur naturalist trying to discover everything living in my garden.

The pretty flower in photo 1 is Cat’s Ear - a common weed in my garden. There are a number of superficially similar British yellow-flowered weeds including the Hawkbits, Sow thistles and the Hawksbeards I blogged here. From my copy of The Wild Flower Key (Rose) I’m fairly confident my plant is none of these, though I’m less confident it is definitively Cat’s Ear (Hypochaeris radicata) and not the rather similar Smooth Cat’s Ear (H. glabra). The book tells me that were my plant to be Smooth Cat’s Ear , then its yellow ‘petals’ would be only twice as long as wide (mine seem longer). Also that the green stems of H.radicata should broaden as they approach the flower head (more correctly ‘the involucre bract’), which appears to be the case for my plant (see photo 2). On this basis I’m going with the identification H.radicata.

Readers of my blog will know I try to do a little research to uncover some point of interest for each lifeform I come across. In the case of Cat's Ear my searches led me to an interesting paper [1] by N. Hartemink et.al. The authors asked the question "What does a plant do if you cut the flower buds off?" (these are my words - I'm paraphrasing). A trite answer would be "Grow some more!". Pausing to consider things in more detail however one might begin to imagine more subtle possibilities. Consider a plant growing in a field subject to heavy grazing by animals. If the plant loses a flower one might imagine various responses. For a short lived annual plant, flowering and successfully setting seed in a season is an absolute imperative. One might conjecture that such plants could respond to flower-loss by "stepping up" efforts to produce more and more flowers therefore in the 'hope' that some escape the grazing (of course plants don't 'hope' and this is a poor anthropomorphic description - but, hey, I'm an amateur and it's good enough for me!). By contrast, for long lived perennial plants, flowering does not have the same urgency. If such a plant has its flowers removed, might it simply 'cut its losses' therefore, put 'on hold' attempts to flower and instead put its energies into growing more leaves and roots?

To add to these considerations, one should remember also that a plant may not have a simple unfettered 'choice' about whether and how many flowers to grow. Resources (food, water and light etc.) are always finite and may impose further constraints on what types of structure (e.g. flowers vs. leaves) the plant is able to produce. A deeper consideration of this resourcing issue has led the experts to formulate such theories as "meristem allocation". (Meristems are specialised regions of a plant where growth 'happens'. Meristem tissue is found at the tips of roots and shoots for example. It is made up of special meristemic cells that are rapidly growing, dividing and transforming into new bits of root, shoot etc.). I don't understand the 'meristem allocation' theory in detail, but briefly it seems to revolve around the idea that a mersitem at the tip of a plant shoot has a 'choice' to simple carry on creating more and more plant shoot and leaves, or cease making leaves and shoots and instead switch to making a flower. Once the meristem has switched to making a flower however, there is no going back - that meristem is committed and can't later go back to making shoot. In a sense the plant's meristems are like cash in a bank. The plant can keep the 'cash' (mersitems) in the bank growing 'interest' (more shoots and leaves) or 'withdraw' (allocate) some money (meristem) and 'spend it' on a flower. This might all seem rather abstract, but the point is that armed with the idea that meristems are a fundamental unit of 'currency' in the 'economics' of plant survival, botanists can start to construct quantitative and predictive (as opposed to merely descriptive) theories of how plants ought to respond to different environmental pressures (grazing, resource shortages etc.).

So, what does a Cat's Ear do when you cut the flowers off?! Well, the authors above took three plant types: Cat's Ear, Devil's Bit Scabious (Succisa pratensis) and Brown Knapweed (Centaurea jacea). They found marked differences in the reponses of these three to removal of flower buds. Both S. pratensis and C. japea responded to flower bud removal by increasing the number of flower buds. Plants of both species would typically make around 7 flower buds per plant if 'left alone', whilst those plants who had their flower buds removed would 'bounce back' and regrow about 12. Interestingly however, S. pratensis also responded by switching some of its energies away from flower bud growth into increasing growth of plant side 'shoots' (strictly side 'rosettes' of new leaves). Appropriately for this blog posting, Cat's Ear's response was the most dramatic all. Plants 'left alone' produced around 60 buds. The 'decapitated' however, bounced back with a dramatic 240. There is much more in the paper that I could talk about, but I've gone on enough here and will simply refer you to the original if you're interested. What I like about the work is it is true science and yet an experiment that any motivated amateur could repeat and extend: find a patch of weeds and a pair of secateurs and you're all set to become a published scientist.

Reference:

[1] Flexible life history responses to flower and rosette bud removal in three perennial herb, Nienke Hartemink, Eelke Jongejans, Hans De Kroon , Oikos 105: 159-167, 2004.

Scenedesmus algae

2011-06-19T13:46:00.001+01:00

I am an amateur naturalist trying to discover everything living in my garden.

Some time ago I wrote about a puddle I spotted in my garden. Of course, I bought it into my house in a fishtank (doesn't everyone do this with their garden puddles?!). It was only last week, nine months on, that I finally returned it to the great outdoors. Amazingly it was still brimming with microscopic 'pondlife', although it had become rather choked with the 'sludgy' cyanobacteria I wrote about here.

Over the months I repeatedly examined my puddle under the microscope. Photo 1 shows one of the lifeforms I found. This one was rather common in the early days, but later seemed to disappear.

Spot something tiny and green under the microscope and its either algae or cyanobacteria. Cyanobacteria tend to be featureless, lacking detailed internal structure, notably a nucleus. The cells here have nuclei however, helping to identify them as algae. (The nuclei don't show up very clearly in photo 1 but by squinting I think you'll be able to see the spherical features towards the centres of the upper three cells).

Turning to my (borrowed) copy of the hefty "The Freshwater Algal Flora of the British Isles" (John, Whitton, Brook) - a 700-page light bedtime read! - I was able to identify my algae as a member of the Scenedesmus genus. Characteristic features are the obviously 'pointy' crescent shape. Also, although I occasionally found single, isolated cells, very often I found 4 (as here) or 8 cells together (about which more shortly...).

Scenedesmus algae are part of the Chlorophyta (= the green algae). They are all freshwater. According to the book above as many as 200 different British species have been reported. However, it's been found that individuals from a species can grow into a variety of different forms as a result of different environmental stresses, so there's suspicion that many of these 200 'species' may not be unique. Furthermore the authors explain that recent scientific studies powered by advances in electron microscopy and modern-day biochemistry are pointing to a need to significantly rethink the traditional classification of many species. (This is happening everywhere in biology these days - see my posting on mushrooms here for example). All this means that although the authors give a key to the 42 British species of Scenedesmus algae they recognise, I've not attempted to pin down the species-identity of mine.

As I've said many times, I'm rarely disappointed when it comes discovering that there is some fascinating or unusual feature in the lifestyle of any creature I come across. Turning to my copy of R.E.Lee's Phycology (a present Christmas-last) it turns out that the fact I frequently saw 4 or 8 algal cells together was no accident. If Scenedesmus is grown in a tank free from predators (such as grazing water fleas) it grows as single isolated 'unicells'. (If you're an algal cell wanting to maximise the amount of sunlight and nutrients reaching you its preferable to keep your distance from neighbours who might otherwise shield or shadow you). However, introduce some predators into the tank and, amazingly, Scenedesmus cells switch to growing in small groups as an anti-grazing defence! In the jargon, a group is known as a coenobium. Some groups also grow long spines, although interestingly the book implies that these are flotation devices to help the colony stay in the light, rather than anti-predator devices per se. The algae are able to detect the presence of predators by detecting chemicals ('infochemicals') in the water that leach from the digestive tract of the predators. Another of nature's tiny miracles!

A Mock Orange Tree - Philadelphus coronarius

2011-06-10T19:03:00.001+01:00

I am an amateur naturalist trying to learn something about everything living in my garden.

Photos 1 and 2, taken a few days ago, shows the Mock Orange (Philadelphus) bush that grows at the back of my garden. It is a large plant (maybe 4m x 4m) and a fabulous site in early summer.

And yes, it smells as gorgeous as it looks! A rich honey/jasmine aroma that wafts across my lawn on summer evenings.

Philadelpus has long been popular with gardeners and plant nurseries stock numerous artificial cultivars. The Mock Orange (genus Philadelphus) and 'true' Orange (genus Citus) are really only distantly related. The genus Philadelphus is part of the large Hydrangeaceae family of plants. I found a species-key here, and my plant keys out as Philadelphus coronarius.

Seeing a thin dusting of yellow pollen on many of the leaves I was inspired to get out my trusty student microscope. I enjoy fiddling around with microscopes and I'm a little surprised that in many years of doing so I've never before looked at pollen. For any beginnner like me who wants to have a go, there are a few tips it may help to know:

Firstly, something I hadn't previously realised is that plants release their pollen in a dehydrated state (15-35% water content is typical [ref.1]). I guess (but don't know) they do this to keep their weight low and so assist their transportation by wind or insects. Also, desiccation may help prolong the active lifespan of the grain. Dehydrated and hydrated grains can look significantly different (see photo 3).

A second thing it helps to know is that pollen grains often have a waxy surface coating. This can be a nuisance for microscopy as it may cause grains to stick together. It also obscures fine surface features of the grains.

Fortunately, both rehydration of pollen grains and removal of their waxy layer is easily achieved by simply wetting them with a few drops of alcohol.

Once you've looked at your pollen slide you can of course simply throw it away. Microscope users will know however, it is possible to make a collection of semi-permanent slides by encapsulating specimens in glycerine jelly. You can buy glycerine jelly especially designed for pollen. The jelly contains red dye that stains the grains and makes it easier to see fine details on their surfaces.

Anyway, photo 3 shows the results of the above: circular/triangular pollen grains about 12microns across.

Seeking to learn some more about pollen, I came across a nice review paper by Edlund et.al. here [ref.1]. The paper highlights various areas where the science behind pollen is unexplored or only partly understood. Take for example the functioning of the outer coating of pollen grains (the exine). This layer can be extremely ornate. Often it is riddled with cavities containing exotic plant proteins. When a dehydrated pollen grain lands on the 'female' stimga in the centre of a flower of the same species, something about the surface of the grain causes it stick fast, when pollen from a different species doesn't. The science behind this 'selective adhesion' is only partly understood.

Once a grain has stuck, chemicals are exuded by the stimga that rehydrate the pollen in a matter of minutes. Once again, this can be exquisitely selective. Two species of pollen grain can be put, side-by-side, onto a single stigma, and only the pollen grain from the correct species will be rehydrated. How nature manages to pull off this clever stunt is again something of a mystery.

With the grain re-hydrated, it germinates and sprouts a single tube that grows its way down the stimga. (There's a fun article by Chris Thomas here that describes how to observe pollen tubes by sprouting grains on a piece of onion skin). Eventually the pollen tube contacts with a female egg at the base of the stigma and the pollen grain sends its DNA down the tube to fertilise the egg. (Pollen grains are a mechanism by which DNA is carried between plants. Its wrong to think of them as 'male sperm' however since a pollen grain is mostly comprised of bundles of 'normal' vegetative plant cells.)

Some plants rely on wind to spread their pollen. Others, animals and insects. Something new I learnt was that one plant- Lagerstroemia - is so keen to attract the latter it produces two types of pollen: a sterile, yellow, feeding pollen and a fertile, blue one.

My first microscope observations of pollen were great fun and I learned a lot. It turned out my Mock Orange had an another interesting microscopic feature for me. What it was however, will need to wait for another posting.

Reference
[1] Pollen and Stimga Structure and Function, A.F. Edlund, R. D. Swanson, Preuss, The Plant Cell 16:S84-S97 (2004)

Hedge Bindweed Calystegia sepium

2011-06-04T17:50:00.001+01:00

I am an amateur naturalist trying to discover everything living in my garden.

Photos 1 and 2 show some Hedge Bindweed (Calystegia sepium) - a weed that pops up frequently in my garden.

My copy of The Englishman's Flora (Geoffrey Grigson) lists dozens of alternative names for this common plant, from the pretty Rutland Beauty, Shimmy-and-Buttons and Robin-run-the-Hedge,to the sinister Devils Garter, Strangleweed and Devil's Guts.

A name not in the book is the one my mother taught - Granny Pop the Bed - so called because if you squeeze the green base of the trumpet shaped head (see photo 2) the white flower pops out. It's not a very convincing pop it has to be said, but hey, when you're six its great!

In the jargon, the green flower base is called the calyx (I've labelled this in photo 2). The 'leaves' that make it up are called sepals. C.sepium also has an outer epicalyx.

When I first started this posting I took it for granted that a web search would turn up scores of scientific papers on my common weed. As it turned out I struggled to find any! I did come across a research paper [1] on the apparently unusual lectin (a protein) biochemistry chemistry of my weed, but the subject matter was rather technical and I'm not expert enough to do it justice here. This aside most of the material I did manage to find concerned the related Field Bindweed (Convolvulus arvensis), a target for frequent study because it is a major weed of arable crops. (Field- and Hedge Bindweed can be readily distinguished by knowing that Field Bindweed doesn't have an epicalyx).

This lack of literature meant that for a time I was left wondering what to say in this post, but then I recalled an unusual fact concerning Bindweed's spiral growth which I'd read about some time ago (I don't remember where). Photo 1 shows a plant climbing a garden cane. As it climbs the stalk is seen to spiral in an anticlockwise direction (as viewed from above). What's interesting is that C.sepium always spirals anticlockwise. (I've even been around my garden checked! Indeed once you know this fact, its hard resist the temptation to check the spiral of every Hedge Bindweed you see anywhere!).

This feature of always twisting one way turned out to be rather a rich topic for exploration. Amongst others I was led to a paper by Thitamdee et.al. [2] on the origins of spiral forms in plants:

The authors' studies focused on plant microtubules. These are molecular sized rods found in both plant and animal cells (they've received mention on my blog before, here). Its been discovered that large numbers of these rods decorate the surface of plant cells (like matchsticks stuck on a balloon). The rods do not lie randomly on the surface of the cells however, rather they order themselves so as to line up along a common direction. There's some amazing video of real microtubules jostling about on cell surfaces on the webpage of Indiana University's Shaw Lab. here. Now, to continue the balloon analogy, imagine having a lot of matchsticks densely glued to the surface of one of those sausage shaped party balloons. Imagine the matches are all lined up so as point around the short, circular axis of the balloon (like hoops around a barrel). Next, imagine blowing more air into the balloon. Though I haven't actually done the experiment, I hope its reasonable to suggest that the rigid matches would make it more difficult for the balloon to swell in circular cross-section (get 'fatter'), and instead the balloon would grow more freely lengthwise (get longer). This is exactly what aligned microtubules are believed to do for plant cells i.e. cells that would otherwise grow and expand as simple spheres are instead constrained to grow and expand along a preferred direction. This is useful because it allows the plant to create e.g. long, thin cells suitable the plant stalk. (Actually, strictly its not microtubles themselves that constrain the growth of the cell walls, rather the microtubles appear to act as markers for the laying down of a secondary stiffening material - cellulose - but the principle's the same)

Now, Thitamdee et.al. were studying a cress plant called Arabidopsiss. This is famous amongst botanists as the plant for genetic studies worldwide. Normal Arabidposis plants don't spiral, they grow straight. Furthermore, when scientists looked at the microtubules on cells in the stalk they found them to be arranged exactly as in the description above (i.e. 'hoops around a barrel')

What Thitamdee et.al. discovered however, was that a mutation in a single gene can cause a change in the way microtubles on cells in the stalk of an Arabidopsis plant arrange themselves. Specifically, they observed mutations that caused the microtubules to shift from being aligned all-parallel to the cell circumference ('hoops around a barrel') to instead all lying on the cell surface at an angle to the long axis of the cell.

And what did these mutant plants, with their slanted microtubles, do? Yep, grow in a spiral!

The importance of this work is that it implies an explanation for why some plants spiral and some don't, and furthermore why, for many species, every individual must spiral in the same direction: Things are dictated by the angle at which microtubles are aligned on the cells. This in turn is hardwired by the plant's DNA. Perhaps an ancient ancestor of Hedge Bindweed grew straight. At some point however a gene mutation arose that caused the microtubles to align at some new angle. With this angle fixed by the DNA, the Bindweed's fate was fixed; Subservient to the constraining forces acting on its cell walls, it was doomed to spiral, and always in the same direction, this being dictated by the angle of microtubule alignment (though what this is specifically I don't know - I haven't found any reference to suggest the microtuble alignment of C. sepium specifically has been studied).

To end, a bit of humble pie. When I first recognised the anticlockwise spiralling of Bindweed, I admit I thought I was rather clever in having uncovered some little known fact... until, that was, I discovered that my supposed 'little known fact' even had its own popular 1950's song!

The fragrant honeysuckle spirals clockwise to the sun,
And many other creepers do the same.
But some climb anti-clockwise, the bindweed does, for one,
Or Convolvulus, to give her proper name...

( from Misalliance by Flanders and Swann, ).

References

[1] The Crystal Structure of the Calystegia sepium Agglutinin Reveals a
Novel Quaternary Arrangement of Lectin Subunits with a Prism Fold, Y Bourne et.al., The Journal Of Biological Chemistry, 279(1),pp. 527–533, 2004

[2] Microtubule basis for left-handed helical growth in Arabidopsis, S. Thitamadee, K. Tuchihara & T. Hashimoto, Nature, 417, p.193, 2002.

A Grey Squirrel Sciurus carolinensis

2011-06-02T22:33:00.002+01:00

I am an amateur naturalist trying to learn something about everything living in my garden.

Photo 1 (strictly I took this particular photo in a local park) shows a sporadic visitor to my garden, and my third mammal, the Grey Squirrel (Sciurus carolinensis).

To learn something about them I have been reading Squirrels by Jessica Holm (Whittet Books).

Together with the Red (Sciurus vulgaris) the Grey is one of two species of squirrel found in Britain. It is a North American import. The first pair was released by a Mr Broklehurst in the county of Cheshire in 1876. Famously, the Grey has thrived (indeed, they are legally classified as vermin), whilst the once common Red is today a protected species clinging on in a handful of isolated locations (I have only ever seen one myself- in Cumbria).

Why the populations have changed in this way is not entirely understood. It is often said (indeed, before reading Dr. Holt's book I too had lazily assumed) that the Greys have 'driven' the Reds from their 'territories'. This is false on two counts however: Firstly, in woodlands where both have been studied together its found that Reds and Greys do not show any undue aggression towards one another. Secondly (and a surprise to me) squirrels aren't territorial animals. The life of a squirrel is a 'roaming' one (though generally confined to some home range of a kilometer or so). Rather than all-out interspecies hostility, it seems that the Red population may have declined as a combination of diseases passed on by the invaders and because the smaller size of the Reds means they are less able to gather food in areas where the more avaricious Greys are eating much of it up. Totally, more study is necessary however.

A few additional things of interest I picked up from my reading are firstly that Reds and Greys normally carry distinct species of flea (Monopsyllus sciuronum for the Reds, Orchopeas howardii for the Grey). Mother Nature is nothing if not an expert in specialisation! Secondly, watching a squirrel work through a pile of nuts, it will sometimes be observed to discard one without opening it. These turn out to be bad nuts with withered kernels. How the squirrel determines this with the nut still in its shell is rather impressive. It weighs them in its paws. A neat party trick!

To end, the literature abounds with Squirrel poems and Beatrix Potter quotes, but for me there is only one winner of the prize for top squirrel literary moment:

The squirrels pulled Veruca to the ground and started carrying her across the floor.
"My goodness she is a bad nut after all" said Mr Wonka, "Her head must have sounded quite hollow" [...]
"Where are they taking her?" shrieked Mrs Salt.
"She's going where all the other bad nuts go" said Mr Willy Wonka. "Down the rubbish chute."
[Roald Dahl, Charlie and the Chocolate Factory]

A long legged Dolichopus fly

2011-05-31T21:50:00.006+01:00

I am an amateur naturalist trying to discover everything living in my garden.

For some time I have hankered after a garden pond (there are few things better for encouraging wildlife into one's garden). On a whim, I recently took the plunge (sorry, terrible pun!) and dug one. Though only a few weeks old, already I'm seeing enough life to keep me busy blogging long into the future.

Photo 1 shows two flies sunning themselves at the water's edge. There were several dozen around the pond.

The 'colony' was a constant flicker of activity and it was this that first caught my attention. Individual flies seemed to be attracted to movement and if another landed closeby they would quickly go 'into action', advancing rapidly towards the new comer. In a few cases one would even jump on top of another and the two launch into flight (at which point it was impossible to follow them by eye).

I observed a number of instances of one fly standing close by another and methodically rubbing its back legs together. I've highlighted this with an arrow in photo 2. I recently wrote at length about the courtship signalling behaviour of a related fly (Poecilobotus nobilatus) I found in my garden. I would like to think I was observing something similar here. Whether I was however, or whether it was just some coincidental preening I can't be sure (can anyone comment?).

So, how about the identity of my fly? Unfortunately, for the non-expert (=me!), identifying a fly is a decidedly non-trivial business. Firstly, a low power microscope is pretty much essential. Next, you need to be fortunate in finding an identification key. After that you need to be prepared to work through the copious technical jargon that the specialist keys will hurl at you. Finally you need the magic ingredient: experience!

How did I fair against this list? Well, I have a microscope; I was also fortunate to find the free online key by Dennis Unwin to the families of British Diptera, and "A Key To Swedish Dolichopodidae" by Igor Grichanov; For several hours I diligently applied myself to translating the jargon in the keys and scrutinising my fly's features. I was able to determine that my fly's "post ocular setae" (=bristles behind the eyes) are long and all of them black (see '1' in photo 3). Also, that the base of my fly's antennae sprout tiny hairs (see '2' in photo 4); that the shape of it's "occiput" (= the back of the head) is convex (see '3') and that it sprouts two rows of "acrostichal setae" (=hairs down the centre of its back - see '4'). I worked through a dozen other similar features.

And the result of all my efforts? Well, further aided by a study of my fly's wings (see my discussion of insect wings here) I'm confident that amongst the 80-odd families of British fly, mine is a member of the family Dolicopodidae. Next, I'm fairly confident that of the 30-odd genera within this family, mine is a member of the Dolichopus genus. And finally, of the 51 British species within this genus (I got this number from the Dipterists Forum website)... well, I am not at all confident (!) mine is a Dolichopus ungulatus.

The one thing you can't look up is experience.

A spider Meta segmentata

2011-04-29T17:10:00.022+01:00

I am an amateur naturalist trying to learn something about everything living in my garden.

Photo 1, taken late last summer, shows a spider about half-a-centimetre long. Spiders are surprisingly tricky to identify. You might think their often striking colour patterns would make things easy. Unfortunately for many species this is rather variable and the only really accurate approach to identification is to examine your arachnid's reproductive parts under a hand lens. I didn't subject my spider to the indignity of this. From the illustrations in my copy of Spiders (M.Roberts, publ. Collins) however I'm tolerably confident the species here is either Meta segmentata or Meta mengei. Both are common in Britain and look very similar. From the season (M. segmentata is more common later in the year and M. mengei earlier) and from the book illustrations which show M. mengei with a more distinctly hairy lower-leg ('metatarsus I and II' - I've marked these with the white line in photo 1) than my spider appears to possess, I'm going with the identification M. segmentata.

The spider here is a male as revealed by the presence of the two little 'boxing gloves' (the 'palps') emerging just in front of the head. You can see these most clearly in photo 2.

In the course of writing this blog I have learnt to expect that any creature I come across will have some complex and fascinating aspect to its lifestyle. As I discovered from browsing various online papers (1, 2, 3 - references below) M. segmentata is no exception. The mating strategy of male segmenta's is one example of the rich topics for exploration:

If you're a male M.segmentata wanting to mate with a female it does not pay to approach her directly. Do this and its likely she'll eat you! Why it benefits some lifeforms to routinely indulge in cannibalism and others (we human males might say, thankfully) not is a puzzle in itself. Anyway, regardless of the reason, the best chance a male M.segmentata has of mating with a female is to approach her at just the moment she has caught a nice juicy fly and is sufficiently pre-occupied not to eat her suitor. In detail, what males actually do is to approach the female on her web, drive her off her catch and cut the threads supporting the dead fly so that it dangles from a single 'nuptial' thread. The male then mates with the female whilst she attempts to recover the catch.

For the male to be present at just the moment a female catches a fly requires that he sits, sometimes for weeks, watching her web. This is known as 'mate guarding' (in my previous posting I discussed mate guarding amongst dragonflies). Mate guarding for male M.segmentata's is a high energy-expenditure task. Not only may his own food supply suffer, but he is also exposed to challenges from other males who want to usurp his position of guarding a receptive female. (It seems that males know receptive females by the presence of pheromones on her web). The whole question of why it pays males in nature to expend considerable energy to mate is a very deep and rich one in biology (I said something about it in my posting here). An illustration of how subtle things can become is afforded by the studies of Rubenstein and others above (ref.1) on M. segmentata:

Careful studies of colonies of M. segmenta (e.g. on an isolated bushes) show that over a season, a 'size hierarchy' develops with the biggest healthiest males taking over guarding the biggest healthiest females. Once a big male has succeeded in mating with a female, he will move on and find another big female to start guarding. He may need to battle with an already on-guard male to win the right to guard this new female, but being large he stands a decent chance of winning any such battles. In this way big males get to mate with lots of big females and enjoy high reproductive success.

Little males have no hope of winning at this 'roaming' lifestyle however. They would constantly lose the battle to guard large females to larger males. So instead, small males adopt an alternative strategy and choose monogamy, 'settling down' with a single small female. Being small, she herself will normally have been pushed out to an 'undesirable' part of the colony (low down on the bush, say) where prey is scarce. Her small size and poor diet will mean she is not likely to be very fertile (she will not produce a lot of eggs). However, in settling down with her the little male avoids the alternative of a series of fruitless battles over larger females.

So far so good, but now, the question arises: What of mid-sized males? Should they roam, continually seeking large, fertile females to guard but mostly losing them in battles with large males? Or do as small males do and 'settle down' with a single female, but at the cost their mate may have low fertility. In the studies of Rubenstein, 86% of medium males opted to roam. Precisely why the odds stack in this direction doesn't seem to be understood; a nice example of how subtle behaviours can be in the natural kingdom and how there are plenty of topics awaiting further study.

References
1. Alternative reproductive tactics in the spider Meta segmentata, D.I.Rubenstein, Behav. Ecol. Sociobiol. (1987) 20:229-237
2. Mate guarding, competition and variation in size in male orb-web spiders, Metellina segmentata: a field experiment. J. Prenter, R. W. Elwood, W.I. Montgomery, Animal Behaviour, 2003, 66, 1053–1058
3. The influence of prey size and female reproductive state on the courtship of the autumn spider, Metallina segmentata: a field experiment, J. Prenter, R. Elwood, S. Colgan, Anim. Behav. 1994, 47, 449-456.

Common Darter dragonfly Sympetrum striolatum

2011-04-23T14:52:00.017+01:00

I am an amateur naturalist trying to learn something about everything that lives in my garden.

Photo 1, taken back in Autumn shows one of Britain's forty-or-so dragonfly species. Referring to the magnificant colour photos in my copy of Britain's Dragonflies (Smallshire and Swash) I'm confident this is one of the commoner species, The Common Darter (Sympetrum striolatum). The yellow stripes down the legs indicate this one is a male. Adult Common Darters can be found on the wing from March through to earlier December if the weather is mild.

Two dragonflies were present the day I took photo 1. This is the first time I have seen them in my garden. About a kilometre from my house there is a large expanse of wetland however and there, at times, I have seen swarms of several hundreds.

To learn something about dragonflies I have been reading the book of the same name by Corbet and Brooks (New Naturalist Series). I particularly enjoy natural history writing that educates you about not only what is known, but also what isn't. The book is fully satisfying in this respect, concluding each chapter with a section 'Opportunities for Investigation', listing projects of genuine scientific value that any sufficiently motivated amateur might tackle.

The book opens with a discussion of habitat selection: Many dragonfly species are selective over the habitats they will adopt as breeding sites. Some demand flowing water, others still. Some require the presence of certain types of aquatic vegetation. Some will select a pond only if the trees on the bank are below a certain height. Etc. It's hypothesised that an adult arriving at a new location runs through a checklist of 'proximal cues': 'Is it water?' -> 'No', then fly on / 'Yes' then 'Is the water flowing?' -> 'No', fly on / 'Yes', then are there trees on the bank... What the cues are for many species isn't understood however. The fact that adults have been observed being fooled into, for example, trying to lay eggs into a wellington boot (!) suggests one line of enquiry might be careful experimental manipulation of environmental cues to try to work out those that appeal to different dragonfly species.

The topic of reproductive behaviour is a very rich one for study. The authors break things down into the four stages of Recogition (of a prospective mate); Sperm transfer; Guarding Behaviour; and Oviposition. Guarding behaviour is the habit amongts the males of many species (including my S. striolatum) of staying with a female even after she has been fertilised. The males of some species continue to grip the female by the head until she has finished depositing her eggs. Some even 'dunk' the female under water to assist her egg laying into the submerged stems of plants. An advantage of guarding from the male's perspective is that it prevents other males from coming along and displacing his sperm with their own. For the female there are presumed survival advantages: Two sets of eyes are better than one when it comes to spotting predators. Some species even go in for group oviposition, whereby half-a-dozen or more males/female pairs congregate in one spot to lay eggs.

There are a great many opportunities for amateur study concerning the larval stages of dragonflies. Dragonfly larvae go through a number of stages called 'stadia', moulting their exoskelton between each. The stadia for many species however, are simply not known. As the book puts it "there is an urgent need for keys to earlier stadia".

Some species go through all development stages in one year, others 'sit out' the winter in 'diapause', still others have the option to do either. Much remains unexplored concerning the factors that control the development rate of larvae and whether they overwinter or not.

Some dragonfly species lay their eggs several metres from the water's edge. How the first larval stadium (a minute limbless 'tadpole') makes its way from the egg-site to the water is again unknown.

Finally, there are many opportunities for studying the behaviour of larvae - their strategies for stalking different types of prey for example - that any suitably motivated amateur armed with a fishtank and plenty of patience could attack.

There is a great deal more that could be said about the study of dragonflies ('Odontology'). Part of me feels I ought to go on and write more here since I have not seen other dragonfly species in my garden and so may not get a chance to return to them on this blog in the future. On the other hand when I started logging my garden's visitors several years ago I never imagined I would find myself writing about peacocks and budgerigars. So perhaps I can afford to take the risk!

Two species of cyanobacteria (possibly Nostoc commune and Anabaena cylindrica)

2010-12-30T21:55:00.028Z

I am an amateur naturalist trying to learn something about everything that lives in my garden.

Some of you may recall that in a recent posting I bought a puddle into my house (it was in a plastic fishtank!). Well, I've hung on to my puddle. Indeed I've been periodically topping it up with fresh puddle-water and inspecting its inhabitants under my microscope. Photos 1 and 2 show two such 'denizens of the deeps'. No, not frog or toad spawn. The scale is all wrong for that. Twenty of the larger spheres in photo 2 for example, would sit side-by-side in 1mm. In fact these are of colonies of blue-green algae (cyanobacteria).

Cyanobacteria are some of the most ancient lifeforms of all. Their microfossil record goes back 2.7 billion years. What I have learnt about them has been mostly through reading a new book - Phycology (=the study of algae) by R.E.Lee (CambridgeUni. Press) - which Santa very kindly delivered to me recently.

Like plants, cyanobacteria carry out photosynthesis. In fact, it is believed that photosynthesis evolved first in cyanobacteria and at some point in the ancient past a cell that was to become the first plant 'swallowed' (co-opted) a cyanobacterium. Chloroplasts, the green organelles responsible for photosynthesis found inside all plant cells are the remnants of these 'swallowed' cyanobacteria.

Today such photosynthetic 'slavery' still persists in the lichens. About 10% of lichens use cyanobacteria to do their photosynthesis (the other 90% use algae).

Photosynthesisis is not the only chemical magic that cyanobacteria have mastered. They are also able to 'fix' nitrogen - that is take nitrogen gas from the air and turn it into an amino acid (glutamate). No higher plants or animals can do this, and a range of plants have formed symbiotic relationships with cyanobacteria to take advantage of this ability. Some plants have special nodules on their roots to house colonies of cyanobacteria. The water fern Azolla has cavities in the leaves. According to the book above, nitrogen fixation by cyanobacteria also plays a fundamental role in keeping the world's 100million square km of paddy fields fertile in areas where otherwise farmers would be too poor to nitrogen-fertilise the soil.

The twin ability of cyanobacteria to remove nitrogen and carbon dioxide from the atmosphere had a profound affect on the earth's early climate. Over eons, cyanobacteria, as the dominant lifeform at the time, transformed an ancient atmosphere rich in CO2 and almost devoid of oxygen into the one we breathe today. A glimpse of what the ancient earth might have looked like can be seen today at Shark's Bay in Australia where warm and salty waters limit other forms of life and allow cyanobacteria to dominate and grow into large, rocky (actually calcium carbonate) colonies called stromatolites - see photo 3 which I'm using under the terms of the Wikimedia free licence. Stromatolites grow slowly and exhibit 'growth ring' like features. Analysis of these has allowed scientists to determine that for example, 1-billion years ago the earth's year comprised 435 days [1].

So, how do you set about identifying the species of a cyanobacterium? The answer is: with difficulty! Like so many areas of biology at present, DNA analysis is over-turning a lot of old species definitions. Things are further complicated by the fact that the appearance (morphology) of a specimen of a cyanobacterium can depend strongly on the conditions in which it has grown. Nevertheless with a little patience it's possible for the amateur (me!) to make a little progress. I've also been fortunate in having been able to borrow a copy of the hefty The Freshwater Algal Flora of the British Isles (Whitton and Brook). Firstly you need to know you're looking at a cyanobacterium. If the cells you're examining show any significant internal structure (especially a nucleus) then it's not a cyanobacterium, and is instead a true algae. Next one needs to take careful note of the detailed shape of the colony. For example, if your cyanobacteria exhibit chain-like growth its important to note whether the filaments branch, whether or not they taper towards the ends and whether or not the cells are encased in any sort of slimy envelope (as they are in photo 2). These features help separate the main genuses. Finally, it's important to note the presence and form of any heterocysts and akinetes. I've labelled these in photo 4. Heterocysts are specialised, largely colourless cells that carry out nitrogen fixation. My impression from the textbooks is that the role of akinetes is a bit of mystery. They have reduced photosynthetic ability and seem to be involved in food storage. Anyway based on these features and Whitton and Brook's book above I'm tentatively identifying my cyanobacteria as Anabaena cylindrica and Nostoc commune. As always I'm happy for anyone out there to correct me.

Finally, one of the most amazing things I learnt about cyanobacteria is the way in which some of them achieve movement. Some species develop tiny gas bubbles (vacuoles) inside the cells that help them float upwards in water to receive more sunlight. More fantastically some species can undertake a form of movement known as gliding. Here the surface of the cells is sculptured in a series of grooves. The grooves may spiral around along a chain of cells. The cell pumps slime into the grooves through tiny pores. If a chain of cells is close to a surface, the flow of slime pushes against the surface and causes the whole filament to glide along over the surface at up to half a mm per second. Hooray for slime power!

Reference
[1] J.P. VANYO, S.M. AWRAMIK Precambrian Research, 29 ( 1985 ) 121-142, STROMATOLITES AND EARTH-SUN-MOON DYNAMICS,

A fungus gnat , Sciarida (possibly Bradysia)

2010-12-23T09:29:00.034Z

I am an amateur naturalist trying to learn something about everything living in my garden.

Buoyed up by my successful (?!) identification of a fly to species level in my previous posting, today I'm taking on a related, though tougher challenge: the little gnat in photo 1 (click on photo's to enlarge). This one was around in my garden mid-May last.

As I've discovered through writing this blog, to stand any real chance of identifying the smaller insects it's pretty much essential to have a microscope. This needn't cost the earth. Photo 1 was taken by holding a 'point and click' digital camera up to the eyepiece of a sub-£100 'DM2' stereo microscope. With 10x and 20x eyepieces this would probably suffice for a fair range of the needs of many amatuer naturalists though if you want to study the more minute structures such as mushroom spores, or the smaller pondlife, a microscope capable of 1000x magnification is needed. I have a (sub-£200) Westbury SP2 microscope which I've found to be thoroughly adequate for all my needs (the only minor drawback, for those in-the-know about such things, is I'm not certain this particular scope has the option to be equipped for 'dark field' operation, though this is a 'luxury' rather than a 'staple'). For anyone considering making a purchase, I have always been very satisfied with the service from Brunel Microscopes Ltd (I am unconnected with the company, and have received no payments for plugging them here!).

To set about identifying my fly I turned first to "A Key to the families of British Diptera" by D.M.. Unwin, available free here. This is designed specifically with the amateur in mind, being copiously illustrated to explain any technical terms. There are more than 80 families of British fly. The fact that my fly has long, thread-like, multi-segmented antennae immediately rules out more than 5o of these however, and places my fly in the nematocera, a sub-order of around 30 families. To distinguish between these its necessary, in part, to carefully examine your fly's wing. In my last posting on a crane fly I discussed the prehistoric origins of fly wings and the so-called 'Comstock-Needham' code for labelling up their veins. I'll not repeat this here and simply point out that I've labelled up the wing veins in photo 1.

With the wings of my fly in view, the key above pretty quickly bought me to a choice of my gnat being in one of two families: the Sciaridae or the Mycetophilidae. The 'decider' was the eyes. Photo 2 (taken from above looking directly down onto the antennae) shows my fly's 'left' and 'right' eyes, though this is a rather arbitrary choice of words since in fact the eyes are joined together to form one continuous band above the antennae. If ever you wanted an example of how 'alien' is the world of insects' senses, surely having eyes that join on top of you're head is one! Anyway, this 'eye bridge' decides against my fly being in the Mycetophildae and makes it a member of the Sciaridae. In searching for information on sciarid flies I came across two useful websites, the first dedicated to Sciariod flies, and the second, a list of free, online keys to different diptera.

The Sciarid flies are sometimes called 'fungus gnats', mushrooms being the larval food for some species. Mushrooms are not the only food however, and species have been reported emerging from a wide variety of substances from dead animals to birds' nests. Perhaps the most amazing thing I learnt about Sciarids in a short time searching is that the larvae of some occasionally undergo mass movements, thousands of them marching in columns several centimetres wide and metres long. I found an online paper reporting one such movement here [1]. It seems no one knows why they do this.

So far so good! Unfortunately, whilst identifying a fly to family level (Sciaridae in this case) is generally tractable, getting much further can be decidedly tricky. The first problem is that there are a lot of families of fly and finding a text-book or key that deals with yours can be difficult or indeed impossible. As luck would have it however, having become interested in flies and having something of a passion for natural history books, last summer I treated myself to some of the Handbooks for the Identification of British Insects from the Royal Entomological Society, amongst them Sciarid Flies by P. Freeman.

The book starts a little ominously:

[Sciard] taxonomy has always presented problems [...] the student has always been faced with a mass of similar looking species which he has been unable to group adequately.

Fortunately Freeman's book provides a detailed guide to identification, covering about half (according to this paper [2], as of 2005 there were 263 species of British Sciaridae in total) the British species across 18 genera.

So how did I get on sifting through the 18 genera of Sciaridae in Dr. Freeman's key? Well, On the basis of wing-vein shape and length, I was able to rule out 4 of the 18 genera; There was no sign of largish hairs ('macrotrichia') on my fly's wing veins, though there were tiny, downy hairs ( 'microtrichia'). This rules out another 5 genera; My fly has tiny spurs on its leg tibia (see photo 1). These are not 'distrinctly longer than the width of the tibia', ruling out the genus Corynoptera. After a little further work I was down to a choice between the genus Bradysia and the genus Lycoriella...and...I dropped my fly on the floor and lost it!!! On the basis of a couple of half-examined features, and the fact that Bradysia is the larger, more common genus, I'm going for Bradysia. But it all goes to show - you can't win 'em all!

Reference
[1] C. T. Brues, A Migrating Army of Sciarid Larvae in the Philippines, Psyche 58:73-76, 1951.

[2] Zoological Journal of the Linnean Society, 2006,146, 1–147. The sciarid fauna of the British Isles (Diptera: Sciaridae), including descriptions of six new species Frank Menzel, Jane E. Smith and Peter J. Chandler

A crane fly Limonia nebeculosa

2010-12-20T15:02:00.056Z

I am an amateur naturalist trying to learn something about everything living in my garden.

My garden, along with the rest of the UK, is currently buried beneath a thick blanket of snow. Aside from a collection of tits on my bird feeder there's little sign of life. For this posting therefore, I'm falling back to a photo of a crane fly I took in summer (photo 1. Click on photo's to enlarge). Dozens of them swarmed out from amongst some garden ivy I happened to disturb at the time.

I know almost nothing about flies (diptera). Along with beetles, ichneumon wasps and various other orders of insect however, they strike me as offering rather "good value" to any amateur naturalist keen to make a genuine contribution to science since a) there are very large numbers of them (15,000 species of fly in Europe alone) b) they can display a rich and complex behaviour (see my posting on P. nobilitatus for example) and c) for countless species almost nothing is known. Take hoverflies for example. After hundreds of years of intense study by armies of naturalists there can be few countries in the world whose natural history has been so well catalogued as Britain's. Further, there are few flies as conspicuous as hoverflies. Yet even for these, a staggering 40% of the larvae of the 265 British hoverfly species of are simply unknown. In the U.S. its 93%. (This, at least, was the situation persisting in 1993 when my copy of 'Colour Guide to Hoverfly Larvae' (G.E.Rotheray) was published). Anyway, we're not here to discuss hoverflies. On to the star of today's show...

What makes a crane fly a crane fly? Well, firstly flies (=the order diptera) are separated from other insects by the presence of two vestigial wings called halteres. I've ringed these in photo 2. Next, the order diptera is separated into two sub-orders of flies called the nematocera and the brachycera. The split is based on the structure of the antennae - the nematocera all have long, thread-like antennae with more than five segments. You can see this in photo 3. The sub-order nematocera gets further subdivided into more than 70 families of fly, the crane flies amongst them. If you want a fuller flavour of how these families are separated, the redoubtable Field Studies Council has made a key to the families of fly by D.M. Unwin freely available here.

It used to be that all crane flies were clumped together in one family called the Tipulidae. At some point however it was decided to split this family into four, the Tipulidae, Pediciidae, Limoniidae and the Cylindrotomidae. I read on the (searchable) Catalog of the Craneflies of the World that worldwide there are more than 10,000 species of Limoniidae, 4000 Tipulidae nearly 500 Pediciidea and 70-odd Cylindrotomidae. Separating these families is a tricky job. To complicate matters further, recent DNA studies [2] are casting doubt on the very existence of the Limoniidae as a family.

The whole thing is rather confusing for the amateur (=me!) and for a long time whilst preparing this posting I despaired of being able to identify my crane fly. Fortunately, rescue was at hand in the form of an excellent set of test keys from Alan Stubbs I found on the Dipterists Forum website.

Before discussing these keys I need say something about how dipterists characterise the wings of flies: An influential theory, originally due to Comstock and Needham in the 1890's, is that way back in prehistory, a first primeval insect wing evolved. Exactly how this first wing appeared is still uncertain but a current theory [1] is that it evolved from the multi-branched external gills seen on the larvae of some aquatic insects such as mayflies. The veins in insect wings are hypothesised to be modifications of these gill 'tubes' (trachea). Anyway, assuming the existence of this ancestral wing, Comstock and Needham named the veins in it the Costa (C), the Radius (R), the Media (M), the Cubitus (Cu) and the Anal veins (A). As these veins fanned out through the ancestral wing they forked. So, for example, the radius vein, R, is supposed to have forked into five sub-veins called (logically enough) R1 to R5. No modern fly has retained all the veins of the ancestral wing, over millenia evolution has caused different families of fly to lose different veins. Which veins a fly has retained however is a very important clue to its identification.

Photo 4 shows the wing of my crane fly labelled up with the help of Alan Stubbs' keys above according to the Comstock Needham system.

There was one more piece of information I needed, namely whether my crane fly's palps (=little facial apendages) were long or short. Photo 5 shows they're short.

Armed with this information I was finally able to identify my cranefly as Limonia nebeculosa. Final 'clinchers' were the presence of 3-coloured bands on my fly's femurs (enlarge to see these in photo 1) and the sort of smudgy 'hoop' on the wing I've delineated with the dashed white line in photo 4.

Today's posting was a bit technical in places but I am pleased to have identified my first fly to species level. Only another 250,000 to go!

References

[1] Averof M., Cohen S.M., Nature 385, 627-630, 1997 Evolutionary origin of insect wings from ancestral gills.

[2] Matthew J., et.al. Phylogenetic synthesis of morphological and molecular data reveals new insights into the higher-level classification of Tipuloidea (Diptera), Systematic Entomology (2010), DOI: 10.1111/j.1365-3113.2010.00524.x

A lichen Malanelia subaurifera

2010-12-11T15:15:00.028Z

I am an amatuer naturalist trying to learn something about everything living in my garden.

Photo 1 shows a lichen growing, amongst a number of similar patches, on a wooden bird table in my garden.

I am very far from being an expert on lichen identification but in the course of doing this blog over several years I have picked up a few tricks. One is to examine your lichen through a hand lens for any characteristic surface lumps on bumps. Some lichen species become decorated with powdery granules called soralia. Others with tiny sausage shaped protuberances called isidia. For my lichen, the latter are present in abundance as can be seen in the close-up Photo 2 (click on photos to enlarge).

Another trick to help with lichen identification is to check the under surface. In photo 2 I have peeled back a small section to reveal a black underside with a covering of tiny, root-like hairs. In the jargon, these are known as rhizines. Not all lichens have them. They are not roots in the traditional sense, since they do not function to suck-up water as do the roots of plants. Rather their job seems to be to help anchor lichens to surfaces.

Armed with the features above and my trusty copy of Lichens (Dobson, Richmond Publishing) I'm confident to identify my lichen as Melanelia (Parmelia) subaurifera. The book suggests a final test: gently rubbing the surface should leave a pale yellow-white abrasion. Photo 4 shows this.

I am fond of lichens and so was very pleased when someone recently made me a present of the new edition of Lichen Biology (Ed. Thomas H Nash III, publ. Cambridge). This book is primarily aimed at professionals and I don't pretend to have followed some of the very detailed sections on e.g. lichen biochemistry, but I was able to follow others and came away with a new respect for the intricacy with which nature adapts these little creatures to their environment. Take for example the construction of the little air-filled spaces often found inside the bodies of lichens:

Under a microscope a lichen is revealed to be a mass of long, spaghetti-like fungal cells ('hyphae'), mixed-through with a sprinkling of green, single-celled algae or sometimes cyanobacteria. (The fungus carries out various tasks such as water storage. The algae or cyanbacteria do what no fungus can: photosynthesise food from sunlight). In considering this description however it would be wrong to picture things as a random tangle of fungal threads and algal cells. Photo 5 shows a lichen cross section I made and discussed some time ago (here) and reveals that things are far from random. Of particular relevance for today's posting is the layer known as the medulla that contains a lot of air-filled voids (see the region of the box in photo 5 for example). What is the purpose of these voids? The answer of course is that algae, like all plants, 'feed' (via photosynthesis) on a diet of sunlight and gaseous carbon dioxide. This is the key to understanding the voids: they are present to allow the flow of gaseous CO2 gas to the algae.

So far so good, but possibly it might occur to you to wonder what happens when it rains?! Do these voids fill up with water and in so-doing stifle CO2 flow, and hence photosynthesis, in the lichen? As I learnt from the book above Nature, of course, has an answer. In one chapter, a remarkable photograph taken by Rosmarie Honeggar with an electron microscope reveals how the fungal threads in the medulla carefully coat themselves and their precious cargo of algal cells in a minuscule layer of water-repellent proteins. This remarkable water repellent 'jacket' prevents the medulla from becoming saturated with water and so maintains the algae in a gaseous environment conducive to photosynthesis.

The water-repelling proteins the fungal hyphae secrete are known as hydrophobins and their discussion would make a lengthy posting in its own right. They were unknown to science until the 1990's when they were discovered by Wessel and co-workers in a fungus called Schizophyllum commune. Since their discovery these remarkable molecules have turned out to be widespread amongst fungi, with fungi using them in a variety of ingenious ways to 'manipulate' the surface tension of watery environments. For example, in order to help their spores get airborne, some plant-infecting fungi coat their spores in hydrophobins so as to prevent them becoming trapped or stuck together by thin films of water. Hydrophobins also help the infectious spores stick to the waxy, water-repellent leaves of targeted host plants. You can find a short introduction and further references on hydrophobins in lichens here ( P.S. Dyer, New Phytologist (2002) 154 : 1–4).

So there you have it! Minuscule, air-filled voids in a wafer-thin lichen...but take a closer look and as so often in natural history, one finds a hitherto unimagined world of subtlety and sophistication.

Greater Plantain Plantago major

2010-12-04T16:53:00.011Z

I am an amateur naturalist trying to learn something about everything living in my garden.

Taken in August, photo 1 shows a specimen of the weed Greater Plantain (Plantago major) growing on my lawn. This plant is very common in the UK and likely to be encountered on any patch of rough wasteland (= my lawn!).

For such a common plant I have found relatively few freely available papers dealing with Greater Plantain on the web. There are a number (such as here and here) that deal with its medicinal properties. Plantago major appears to have a long list of antibacterial, antifungal and antitumeral properties and has even been recommended to treat the bites of rapid dogs! Amongst the interesting snippets I picked up from skimming the paper by Velaso-Lezama et.al. [1] is that Greater Plantain is today used as a medicinal tonic in Mexico having been originally introduced there by the Spanish conquistadors.

A number of species of Plantain grow in the UK including Ribwort- and Buck's Horn- , both of which have narrower ('lanceolate') leaves than Greater Plantain. Also Hoary Plantain (Plantago media) which as the name implies differs from Greater Plantain in having greyish down on the leaves. That at least is how things are set out in my copy of The Wild Flower Key (F. Rose, publ. Warne). If however, the Plantago media above is one and the same as the Plantago intermedia described in this paper [2] by El-Bakatoucshi et.al., then these authors cast doubt on whether major and intermedia are sufficiently distinct to be regarded as separate (sub) species.

In skimming the paper above by El-Bakatoucshi et.al. , a word I came across that was new for me was protogynous (in context: "Plantago major is protogynous"). A little research and I now understand what this means. I'll share it here for interested readers: Firstly one has to recall that for many plants, the flower is typically neither male nor female. Rather the same flower combines male pollen producing parts (the anthers) and a female reproductive part (the stigma). This gives plants an issue of how to avoid self-fertilisation (i.e. self pollination). Plants have come up with a variety of solutions including i) Ignore the problem (= allow self pollination) ii) Separate your line into two, so that some plants carry only male and others only female parts (these are the so-called dioescious plants - from the Greek "two houses" . Our old friend the stinging nettle is an example) iii) Develop some "chemical / structural" approach that avoids self pollination. I wrote about a classic example when I discussed the two types of primrose, 'pin' and 'thrum' iv) Separate the time at which the male and female parts of a flower are active / receptive. This latter method ('iv') is protogyny and is the technique adopted by Greater Plantain. The female stigmas of Greater Plantain flower are protruded 1-3 days before pollen is produced and in this way the chances of self pollination are reduced. Another of those small but elegant behaviours Mother Nature has carrying on all around us.

References
[1] Effect of Plantago major on cell proliferation in vitro R. Velasco-Lezama et.al., Journal of Ethnopharmacology 103 (2006) 36–42

[2] Introgression between Plantago major L. subspecies major and
subspecies intermedia (Gilib.) Lange. in a British population, R. El-Bakatoushi et.al. , Watsonia 26: 373-379 (2007)

Smooth Hawks-beard Crepis capillaris

2010-10-13T21:47:00.044+01:00

I am an amateur naturalist trying to learn something about everything living in my garden.

I have mentioned previously that the pleasure for me in maintaining this blog is that some previously unnoticed (by me at least) plant or insect, once researched, takes on a whole new aspect. So it is with today's posting. A scattering of facts about the genetics of an inauspicious weed may seem obscure to some, but for me, a weed on my lawn catches my eye with a new interest these days. Photos 1,2 and 3 shows said weed. It pops up frequently in my garden.

For the unskilled amateur botanist (=me!) identifying yellow flowered weeds isn't altogether trivial as the guide books contain a long lists of yellow-flowered ragworts, fleabanes, marigolds, colts-foots, dandelions, sowthistles, cats'-ears and hawkbits. After a little work however I'm fairly confident my plant is none of these and is instead Smooth Hawks-beard (Crepis capillaris). A characteristic feature of the Hawks-beards are 'involucre bracts' (=the little leaves around the base of the flower head - best seem in photo 2) organised in distinct inner and outer rows.

Surprisingly, although it is a common UK weed, I've been able to find almost no detailed online information on Smooth Hawksbeard. One exception is the bioimages site that lists a handful of fungal rusts (including some Puccinia species - see my post here) and a gall fly known to parasitise Hawksbeard. The other exception was an online paper by Oud et.al. [1] that describes the chromosomes of C. capillaris. With my comments of the opening paragraph above in mind, its this I'll discuss.

As most people know, the DNA inside cells is packaged into structure called chromosomes. When new cells are needed by a body, the existing cells set about creating copies of themselves by dividing into two, in a process known as meitosis. (Cells destined to become specialist structures such as sperm or eggs do something slightly different called meiosis, but never mind that here). To create two cells from one its clearly necessary to replicate the DNA. To do this the chromosomes perform a complex little 'dance' inside the cell in which they double in number (in a process called interphase), pair up and line up along of the middle of the cell ('prophase' and 'metaphase' respectively) and finally split apart ('anaphase') as the cell separates into two ('telophase').

I got the hang of this terminology recently using my colouring crayons! (I've a copy of the very clever - 'The Botany Colouring Book', Young - in which you learn by doing). You can find any number of explanations on the web however (here for example).

It's perfectly possible to watch the whole miraculous 'chromosomal dance' down a hobbyists microscope. The classic place to look is at the growing tip of a young plant root where new cells are being feverishly created to grow the root. Indeed, I've tried looking for it myself a few times. I've yet to succeed in getting any really good results, but rest assured when I do there'll be a posting...

I can't resist a small digression at this point to mention microtubules. When it comes to pulling chromosomes apart (i.e. during anaphase), cells do this by strapping tiny cables (microtubules) to chromosomes in a process akin to hauling logs out a log pile by pulling on ropes. These microtubules are tiny (around 25nm across where a 'nm' is a millionanth of a millimetre) and hollow. So tiny are they that some physicists (notably the famous blackhole physicist Roger Penrose) have even speculated that inside microtubules, reality ought to be dominated by the small and weird world of quantum physics (cats being both alive-and-dead; particles being in two places at once - that sort of thing) and that signals propagating inside microtubules in the brain might have something to do with the mystery of human consciousness (you can listen to Penrose give a lecture on it here). Anyway, this is a highly contentious claim and a long way from today's discussion. To return to more certain issues:

In their paper above Oud et.al. set out to study the three-dimensional arrangement of chromosomes inside replicating cells during prophase. It turns out if you want to study chromosome arrangements inside a cell without being mired in complexity, you can do worse than make use of Smooth Hawks-beard since it has a mere 6 chromosomes (strictly one should write '2n=6' - see my previous explanation here). Compare that with humans with (2n=) 46, or some ferns with around a thousand! (I have no idea why there is such variation in nature. Generally, there is no relationship between the number of chromosomes and the complexity of an organism. Anyone?).

Trying to image the three-dimensional arrangement of tiny objects is not simple when you remember that looking down a conventional microscope all you see is a flat, two-dimensional view of an object. To achieve a 3D visualisation of chromosomes Oud et.al. used a special type of microscope known as a confocal scanning laser microscope. As anyone who has a normal microscope knows, images suffer from a limited 'depth of field': only a portion of your object appears in focus. Other parts of an object, at different depths, appear blurred. Often this is a nuisance, but confocal microscopes cleverly use it to advantage. They physically block out light from anywhere other than the one extremely thin section of a sample that happens to be in focus. The advantage of this may not be immediately clear, but the point is that by slowly varying the point of focus, one can build up a stack of images where each image contains only light coming from that single, selected slice through the sample. By taking a bunch of such images from different depths, and stacking them all together (using a computer) one arrives at a three dimensional image.

Using this method Oud et.al. arrived at the wonderful picture of the three dimensional arrangement of chromosomes in a Smooth Hawks-beard root cell in their paper. Of course, their study was not about making 'pretty pictures'. They were interested in adding to biologists' long-standing interest in knowing how chromosomes are arranged in space inside the nuclei of cells; In particular whether the arrangement is random or not. Their conclusion (as I understand it) was that although a range of differing arrangements were observed across cells, overall the chromosomes seemed to arrange themselves in space in a finite number of non-random ways.

So there we have it! A week ago, for me, an unknown weed. Now, a named plant with a intriguing inner life. Bye for now.

Footnote:
I have begun to think that my habit of normally giving only a link to articles isn't the best, as articles may disappear online in future. From now on therefore, I'm going to make an effort to selectively include proper references at the end of postings. To that end:
[1] Oud JL, Mans A, Brakenhoff GJ, van Der Voort HT, van Spronsen EA, Nanninga N. Three-dimensional chromosome arrangement of Crepis capillaris in mitotic prophase and anaphase as studied by confocal scanning laser microscopy. J Cell Sci. 1989 Mar;92:329–339

A Rotifer, Genus Mniobia

2010-10-10T12:43:00.069+01:00

I am an amateur naturalist trying to discover everything living in my garden.

Autumn has arrived in the UK. The leaves are dropping from the trees and the wet weather has created puddles of rain water and detritus in my garden. Hoping to investigate the life therein, and having a cheap plastic fish tank to hand, rather than stand outside getting wet I decided to bring a puddle inside. It makes rather an attractive room feature don't you think?! (Photo 1).

Photo 1 shows one of the inhabitants: a rotifer.

Rotifers have long been a favorite of amateur naturalists. Under the microscope they have instant appeal. Take a drop of pondwater and you'll find smaller creatures swimming around (algae, protozoa, fungal spores...) but all tend towards the 'minimalist', typically a single, roughly spherical cell. Rotifers by comparison have a true multicellular body. The amateur gets to search for eye spots, 'buccal tubes', kidneys, ovaries... add to this the wonderful, whirling 'wheel organs' at the front of the head, setting up eddies in the water and dragging hapless prey into the mouth and onwards to the tiny but perpetually snapping jaws ('trophi'), and you have a recipe for many hours of fascinating microscope viewing. In photo 1 I didn't manage to capture the 'wheel organs'. There are some virtuosic photos by Charles Krebs here. Ultimately however there's no beating moving images, these being a fine example.

When it comes to identifying my rotifer I don't have any dedicated books. I did find a basic key in my copy of Microscopic Life in Sphagnum (Marjorie Hingley, Richmond Publishing) however. Some of the features of importance for rotifer identification include the presence of any hard shell ('lorica') and the presence of any eye spots. Mine has neither. The foot is another important feature. My rotifer crawled around 'inch worm' fashion beneath a microscope cover slip and obligingly gave me the views in photo 2. The labelled features point to my rotifer being in the genus Mniobia. As always, I'm happy to have any reader correct me.

The professionals too have given their attention to rotifers. One feature that has provoked serious study has been rotifer sexual reproduction. For many rotifer species, males are very rare. For some, no male has ever been found. How and why rotifers accomplish this, when almost everywhere else in the animal kingdom evolution has rendered reproduction reliant on two sexes, has been actively researched. I considered making this the topic for today's posting. I decided instead however to talk about some experiments into rotifer populations by a Professor Gregor Fussman and colleagues (very helpfully Prof. Fussman has made his all papers available online here).

Biologists have long been interested in trying to model the dynamics of populations. Suppose an isolated island starts out supporting a population of, say, a hundred rabbits and ten foxes. Biologists would like to be able to predict how many foxes might exist on the island a certain number of years into the future. The non-mathematically-minded amongst you (the others might want to skip this bit) might be puzzled by the meaning of the word "model" in the sentence before. Basically it means this: Take a pen and paper. In the middle of your page write an equals sign ('='). On one side of the equals-sign write a letter ('f' say) to represent the thing you're trying the predict (here, the rate at which the fox population is changing). On the other, write all the stuff you guess 'f' depends on - for instance, one might guess the size of the fox population would depend on the size of the rabbit population, the breeding rate of foxes, the old-age-limit of foxes etc. Finally, take the equation you've by now written down, and stuff it into a computer (i.e. tell the computer to plot a graph of the fox population over time using your equation). Of course there are many subtleties and details in order to do this sort of thing well, but in principal at least that is how population models are done.

Rather than 'foxes', Fussman and colleagues set out to model a population of rotifers (Brachionus calyciflorus). The rotifers were feeding on algae ('the rabbits') called Chlorella vulgaris not unlike the alga I blogged here. Rather than an 'isolated island', the environment was a 'chemostat' which is basically a fancy fishtank with tubes in and out in order to controllably input and extract nutrients for the algae to feed on ('grass for the rabbits'). Fussan and team wrote down a set of equations they presumed took account of all the factors that would influence the population growth of their rotifers and fed their euqation into a computer. When the computer results were compared with real life however, they got a surprise: The predictions of their model were in gross disagreement with experiment.

In a textbook example of the scientific method the investigators set out to track down the 'missing ingredient' from their equations. The answer, when it was found, was sufficiently surprising and profound to ensure its publication in the prestigious journal 'Nature'.

The hidden factor influencing their population experiments could be summed up in a word: Evolution. This was a great surprise. After all, the effects of evolution are only 'supposed' to show themselves only over millenia. Evolution doesn't go around dominating the behaviour of fishtanks over a period of a fortnight, right!? What was going on? The answer was subtle: It turned out that the algae in the chemostat occurred in two subtly different forms - the species existed as two clones (I'll call them 'A' and 'B' here). Although only a little different, it transpired that rotifers were unable to 'go forth and multiply' when feeding on one of the clones, 'A', but could happily do so when feeding on the other ('B'). When a population of predatory rotifers was introduced to a population of algae, at first there would be plenty of both types of clone. The hungry rotifers would start to feed on the B's and the rotifer population would grow. Simulataneously, the population of 'A' algae would also grow as they carried on reproducing, free from predation. By contrast, alga B's population would fall, not only because they were being eaten up by rotifers, but also because the bugeoning population of 'inedible' A's was using up an inreasing amount of the tank's nutriants. Eventually the population of 'B' could crash to zero...

...And there it was: Darwin's famous "survival of the fittest" acting on a small difference between two sub-species so as to drive one to extinction in mere weeks!

Actually, my explanation above is oversimplified. In fact the B's didn't always disappear. Sometimes, it was the rotifers whose population would crash as they ran short of food as the B-algae became scarce. The disappearance of predators would then give the 'B' algae the chance to recover. Rather than complete extinctions, the experimenters often observed more complicated oscillations in population sizes in their tank therefore. Nevertheless, once suitably analysed, the conclusion was the same: Evolution was a powerful force at work in their system.

The implications of this discovery for biologists seeking to model important systems may be very large. If evolution is a driving force for the dynamics of algae in a fishtank on short timescales, is it also an important, fast-acting player in such vast and critical eco-systems as the oceans' plankton food chains?

I don't know the status of this last suggestion. I do know however that these days a humble puddle in my back garden evokes a new fascination. Hoorah for natural history!

A lichenicolous fungus Illosporiopsis (syn. Hobsonia) christiansenii

2010-10-02T13:06:00.058+01:00

I am an amateur naturalist trying to learn something about everything living in my garden.

No, not another lichen posting! Instead, the star of today's posting - the pink blobs in photo 1 - is a fungus. Specifically a lichenicolous fungus (from the Latin colous = living amongst [lichen]).

The lichen being infested here is our old friend Physcia tenella.

Photo 2 shows the rather lumpy, 'coralloid' texture of the fungal blobs close up.

I first noticed pink blobs of this type some years ago on a country walk. I struggled to identify them for a long time but an acquaintance suggested the fungus Marchandiomyces. Searching the internet for more information led me to the very nice website of Alan Silverside. There I found pictures of two species: the rich-pink blobs of M. corallinus and the orangey-pink blobs of M. aurantiacus. I was ready to settle for one of these, but then I noticed a comment alluding to yet another pink-blob species called Illosporiopsis christianesnii. (There is yet another called Hobsonia christiansenii - but as far as I can tell this and Illosporiopsis are the same).

Distinguishing between these various blobs seemed a forlorn hope. As it said in a paper by Sikaroodi et.al. (Mycological Reserach, April 2001) I came across during my searches

"These [species] are frequently misidentified because of a paucity of morphological characters"

I was about to quit, but then I caught sight (here and in a paper by Lowen et.al. Mycologica 78(5), p.842) of a mention that the 'conidia' (= asexual spores) of I. christiansenii had a characteristic 'spiral' appearance. I took a tiny part of my fungus in a drop of water, squashed it between a slide and cover slip and viewed it with my trusty student microscope. The result is shown in photo 3 (click to enlarge).

I'm not expert enough to be confident of what I'm really looking at here. Furthermore, working at x1000 magnification is a tricky and frustrating business - there's hardly any depth of focus and the slightest knock sends things scudding out of the field of view. Nevertheless I was left pretty confident there were indeed some spiral 'objects' in my sample (the object in the photo inset for example, and another in the main image above the number '3'). On that basis I'm identifying my fungus as Illosporiopsis (syn. Hobsonia) christiansenii.

Searching more generally for information about lichenicolous fungi I was rewarded by finding the splendid review article by Lawry and Diederich here. From this I learn that the whole research topic of lichenicolous fungi is enjoying a purple (pink?!) patch. From a single illustrated species (a gall on the lichen 'Usnea') in 1792, the number of known species grew steadily to reach around 686 in 1989. Over the past 10-years however, as scientists around the world have started look in earnest for such lichen-loving fungi, the number of known species has more than doubled.

With this explosion in species-count is coming a growing appreciation of just how rich a field-of-enquiry the lichenicolous fungi represent. Take the task of unravelling and understanding the interactions between the attacking fungus and its target lichen. Some fungi are very unfussy, being adaptable to a wide range of lichens. Others have a very intimate and specific relationship with only one or two hosts. Some invaders aggressively attack and kill their target lichen. Others are parasitic, insinuating their hyphae (=the long tube-like cells that make up a fungus) into the cells of their host to suck the juices, vampire-like, from their cells. Some lichenicolous fungi even stage a 'take-over' bid: A lichen is basically a fungus that is 'farming' a crop of algae (see my post here). The game plan of some lichenicolous fungi is to kill the 'farmer'-fungus' in order to acquire his algae.

There are more questions over how lichenicolous propogate and spread themselves. It's hypothesised that some may hitch a lift with roving, lichen-feeding mites. But generally not much seems to be known. There are unanswered questions about the sensitivity of lichenicolous fungi to air quality. Certainly some lichens are incredibly sensitive to impure air, unable to survive even trace amounts of pollution. Whether this holds for their attackers isn't known.

There are further questions about how lichenicolous fungi affect the ecology of a region. It's been argued by biologists that having a lot of parasites in some eco-system ought to encourage a lot of species diversity. Whether this is born out in regions where parasitic lichenicolous fungi are prevalent however is not well studied however.

These topics (and a lot more) are discussed in the review above. All in all, I suspect that any amateur naturalist hoping to make some genuine and lasting contribution to scientific understanding could do worse than to cultivate an interest in lichenicolous fungi!

To return to the pink blob species M. corallinus and I. christiansenii, and the paper I mentioned above by Sikaroodi et.al., a remarkable thing to learn was that these two nominally identical blobby fungi in fact represent two entirely separate fungal kingdoms. There are millions of species of fungi, but (crudely) they can be split into two huge groups. There is a huge group of fungi that grow their spores inside little sausage-shaped bags called asci (see photo 4 on my posting here). Such fungi are termed ascomycetes. The other group grow their spores, not inside asci, but on the ends of sausage-shaped protruberences called basdia. Such fungi are termed basidiomycetes. From everything I've read this is a very deep and ancient division, the ascomycota and basidiomycota representing an ancient 'parting on the ways' in the evolution of fungi. What's surprises me therefore, is that whilst M. corallinus and I. christiansenii seem almost indentical in every regard (both are small pink blobs, and both grow on the same types of lichens), whilst the former is a basidiomycete the latter is an ascomycete. Now, sometimes, entirely different lifeforms can end up evolving very similar bodies simply because these are the best bodies for the life they're trying to live ('convergent evolution'): Think 'whales' and 'fishes' or 'birds' and 'bats'. Have two very distant fungal cousins independently evolved the conclusion that if you want to survive on lichen, being a small pink blob is a good way to go? The plot only thickens when you learn that although DNA testing shows the species above to be members of the basidiomycota and ascomycota respectively (and therefore that they should grow their (sexual) spores in quite different ways) in fact for neither species has this (sexual) fruiting stage ever actually been seen! (Though it should be remarked that the same was true of the blob M. aurantiacus until recently when a fruit body ('teleomorph') was discovered by Diederich and co workers).

So there we have it. A tiny inconspicuous fungus occupying the (to our human eyes) minute and obscure niche of subsisting in the crevices of a lichen. And yet what a rich and unexplored natural history awaits.

"Great fleas have little fleas upon their backs to bite 'em,
And little fleas have lesser fleas, and so ad infinitum"
( Augustus de Morgan, 1806-1871)

Meadow Brown Maniola jurtina

2010-09-30T09:04:00.021+01:00

I am an amateur naturalist trying to identify and learn something about, everything living in my garden.

At the risk of butterfly-blog-overload ("Impossible!" I hear you cry) photo 1 follows on from my last posting and shows a Meadow Brown (Maniola jurtina). The photo was taken late last summer.

The Meadow Brown is fairly easy to identify, though it is worth checking you are not looking at a Gatekeeper (see my posting here) or Ringlet (some photos here).

My specimen here is tattered and faded - not uncommon for the Meadow Brown in late summer. Earlier in the season the upper parts of the wings would have been warm orange.

As with my Red Admiral last time, most of what I've learnt about my butterfly is taken from the splendid new book The Butterflies of Britain and Ireland (Jeremy Thomas and Richard Lewington, British Wildlife Publishing). Unlike many guidebooks, which merely supply you the name and a few scant details (foodstuff etc.) for your specimen, this book sets out to survey the literature and provide a scholarly essay on the natural history of each butterfly individually (not unlike what I aspire to do on my blog, though I don't for a moment pretend to the same levels of completeness or professionalism).

The Meadow Brown turns out to have a particularly rich history of scientific study. In particular it was extensively studied in the 1950's by the famous lepidopterist E.B. Ford and co-workers who were attempting to bring a new, quantitative understanding to genetics and evolution. Butterflies and moths make very good subjects if you want to study evolution: Their lives are relatively short thereby permitting one to follow some feature of interest across multiple generations. And at the same time, variations in their colourful wing patterns give you a very obvious and visible 'signature' that you can set about trying to relate to their genetic makeup.

Ford and others were interested in a wide variation that occurs in the number and spacing of some black spots that appear on the underwings of Meadow Browns. Unfortunately my Meadow Brown wouldn't stay still long enough for me to get a non-blurred photo of these but you can just about make out some spots towards the bottom of the wings in photo 2 (click to enlarge).

At this point I can't resist a small digression to talk about about E.B. Ford. A professor at Oxford University, by many accounts Ford seems to have been a somewhat 'difficult' character. He seems to have been not at all fond of women. He campaigned strongly against their being accepted to the then, all-male, college of All Souls. I also recall hearing somewhere he once refused to give a lecture on the basis that only females had turned up and that therefore there was no one 'worthy' to receive it! (I should add that I have failed to find a reference on the web to back-up this second story. I hope I am not falsely maligning Prof. Ford by it. If someone tells me it's incorrect I'll certainly take it down).

I have not found any free online archive of Ford's papers (anyone?). Whilst searching however, I did find an excellent and comprehensive archive of the papers of Ford's long-time co-worker R.A. Fisher here. (The good people of the University of Adelaide seem to be suffering from the strange delusion - shared by too few UK universities and institutions- that having presumably paid for some piece of university research in the first place, tax payers should get the chance to read the results without having to pay a second time to some private journal publishing house for the privilege!)

Anyway, getting back to the Meadow Brown. Through their work, Ford and others discovered some intriguing and puzzling trends in the wing-spot variation of this insect. They discovered, for example, that the typical spot pattern of Meadow Browns on small islands differed from that on larger islands. The question (unanswered at the time) was why?! What were the evolutionary causes and benefits driving this variation?

As the book above explains, answers only really emerged much later. The studies by Paul Brakefield were particularly important (you can find one of his papers here). It has become clear that spot variation is linked to habitat, in particular the extent of the ground-cover available in some region. Butterflies living in an area with lots of ground cover (long grass) can spend a lot of their time hidden away. For these butterflies, lots of spots would be a positive hindrance - if anything likely to 'blow their cover' to predators. Butterflies from areas with lots of long grass tend to lack lots of small spots therefore. They retain the big 'eye spots' seen in photos 1 and 2, but when resting in deep grass keep these hidden away behind their lower wings, bringing them out only as a 'startle measure' to frighten predators if they are attacked (I spoke more about eyespots here).

On the other hand, butterflies living in areas of sparse, grazed, or stunted vegetation (a small, wind-swept island as in Ford and others' study above for example) are forced to spend much of their time 'out in the open'. Such butterflies tend to have a lot of small wing spots. The reason is that these act as an 'always on' predator defence; An attacking bird is drawn to peck at the black spots on the 'expendable' wing tips, reducing the chance that the insect's precious head or body will suffer the first attack and thereby giving the butterfly the chance to escape attack with only minor damage.

There is much more than could said, especially about some further differences between male and female Meadow Browns. The former need to spend more time 'on the wing' and hence benefiting from some further differences in spot pattern. Since the authors above have already done it so much better than I might howver, I'll stop here, refer you to their book, and, apropos of nothing, end with a quote from the great P.G. Wodehouse:

The least thing upset him on the links. He missed short putts because of the uproar of butterflies in the adjoining meadows.

Red Admiral Butterfly Vanessa atalanta

2010-09-25T17:53:00.019+01:00

I am an amateur naturalist trying to learn something about everything living in my garden.

Taken last summer, photo 1 shows a butterfly basking in the sun on my garden table. There's no mistaking it as a Red Admiral (Vanessa atalanta).

What I have learnt about Red Admirals I have got from reading my newly acquired copy of The Butterflies of Britain and Ireland (Thomas and Lewington, publ. British Wildlife Publishing). This is a major new work that I can't recommend too highly for the interested amateur. All 72 'properly recognised' species of UK butterfly, each copiously and beautifully illustrated as egg, adult, caterpillar and chrysalis, and each with a full and scholarly essay on its natural history.

In common with the Painted Lady I blogged here, the Red Admiral undergoes a remarkable migration. Red Admirals overwinter in Southern Europe, not as adults, but as caterpillars, maturing slowly in the cool Southern winters. In early spring the (by then) adult Admirals start to fly North. Some will fly as far as Scandinavia.

When they arrive at a suitably Northern destination, the males set up territories on high ground where they mate with females which go on to lay their eggs, singly, on plants such as nettle (see my posting here). Eggs hatch after about a week and the emerged caterpillers mature over about a four week period. The caterpillars carry a dozen or so sets of bristles along their bodies and come in two forms: black and green. They have the evolved the remarkable trick of constructing a 'tent' of leaves, sewn together with silk (there's a picture here). Sitting inside they can munch away out the sight of predators. The caterpillars pupate in an attractive grey and yellow-spotted chrysalis to emerge to later as the beautiful butterfly of photo 1. Around October, as the weather cools, these adults fly to back to Southern Europe and the cycle begins again.

The book above mentions a fascinating puzzle for a population of Scandinavian Red Admirals. Leaving Scandinavia at the end of summer the adults start out by flying due South. After a time however, they reach the coast in Southern Sweden. At this point the butterflies 'cleverly' turn West in order to minimise the distance they need to fly across open sea before reaching land again at Denmark. From Sweden, the coast of Denmark is 24km away and only barely visible to human eyes in a fine day. How the butterflies are able to detect it and know to turn West therefore is a puzzle. It is speculated that they may be making use of an ability of many insects have to see the 'polarisation state' of light. 'Polarisation' is a property of beams of light that humans can't see, but suffice to say land and water can affect it in different ways. It is theorised the migrating Scandinavian Red Admirals are using this to aid them in detecting land at a distance. This appears to be unproven however. Another of nature's mysteries!

A lichen: Lecidella elaeochroma

2010-09-17T20:24:00.073+01:00

I am an amateur naturalist trying to discover everything that lives in my garden.

Once upon a time there was a large, upright apple tree in my garden. And then quite suddenly, one night, there wasn't!

What happened is a story most relevant for this blog...but one for another time. For today let me remark only that this calamity gave me an unprecedented opportunity to inspect my tree's upper branches for one of my favourite lifeforms - the lichens.

Photo 1 shows a lichen new for this blog (the grey smudge that is, the yellow is Xanthoria parientina I've blogged previously). Photo 2 shows a closeup of my lichen's areolate thallus (=cracked surface) and black, lecideine apothecia (= fruit bodies - see my artwork and explanation here).

Despite my fondness for lichens I am very far from being an expert. One problem facing the amateur is that many species look rather similar to the eye. Some are all but impossible to separate by anyone who does not happen to possess a forensic chemistry laboratory. (This is not a joke. It is not uncommon for the professionals to turn to e.g. chemical chromatography in pursuit of accurate identifications of lichens).

Fortunately there are a few 'tricks' available to the amateur. One is to observe your lichen under UV light. This is not as difficult as it sounds. In my case a battery-powered banknote reader from a 'pound store' (that's 'dollar shop', '100yen shop'... to those of you reading overseas) yielded the rather lovely result at the bottom of photo 2. The point is that had my lichen been the superficially similar Fuscidea cyathoides (picture available here), also occasionally found on wood, then UV light wouldn't produce the glow seen here. In the jargon, F. cyathoides is 'UV-' . By comparison, as I learnt from to my copy of Lichens (Dobson, Richmond Publ.) the common UK lichen Lecidella elaeochroma is 'UV+ orange' - clearly a good fit and my identification for today (as always I'm happy to be corrected).

I have mentioned previously a question that I have puzzled over regarding lichen: My (decidedly amateur) understanding of evolution has always been that, over time, it drives species towards adopting the optimal form for surviving in their environment. What has puzzled me is how then, it can be commonplace to see lichens with really quite dissimilar features occupying the same environmental niche. Inspect a few twigs on a tree and it's really not uncommon to find, side-by-side, both crustose (pancake-like) lichens, and, as here say, the bright yellow, foliose (=leafy) lichen X. parientina. To survive on wood, how can it be 'evolutionarily optimal' to be a bunch of bright yellow flakes, and optimal to be a grey pancake. Surely one ought to have 'won the argument'? It was satisfying recently therefore to come across a section in the book Introduction to Bryophytes (Vanderpooten and Goffinet, publ. Cambridge) that I think has given me the inkling of a solution to my confusion.

The book describes how some species of moss have become expert in seizing the opportuntity to colonise fleeting, virgin, environments. A newly appeared patch of burnt ground after a forest fire for example. Clearly being 'first moss on the scene' has the benefit you will enjoy the resources of your new home free from the pressure of competition. There is a price to pay for such a lifestyle however. To succeed at rapidly detecting newly emerged environments requires that you to put a great deal of your energies into sending out countless 'scouts' (a.k.a. spores) to explore your environs. By definition, if you're putting your energies into volume spore production, you are precisely not putting them into your own growth (producing lots of leaves etc.). Such 'fugitive mosses' therefore tend to be slight, quick-to-mature, normally annual plants, producing large numbers of small 20um spores.

Now 'fugitive' is not the only survival strategy amongst mosses. Enter the dominants. Dominants aim to out-compete other mosses for light and nutriants by growing faster and larger. This is a perfectly reasonable strategy, but again has its limitations. By investing a large proportion of their energy into the rapid growth of leaves etc. such mosses are left with little energy for the production of spores. Dominants then, will be less successful at rapidily discovering new areas, and tend to be larger, perennenial mosses with fewer spores. This is far from the complete story. As well as doimants and fugitives, the book above goes on to discuss the strategy of 'colonists', 'perennial stayers' and 'annual shuttles'. I have not found any freely available articles discussing similar issues for lichen (anyone?), but I think its not unreasoanble to suppose some similar ecology might hold for these fellow tree- and rock-dwellers.

All of which brings me back to my puzzle of how evolution can have a arrived at two such different forms (body shapes and colours) as optimal solutions for lichens living in the same place (a twig). I don't pretend a complete answer, but I feel I may have started to get an inkling of understanding. I think my confusion likely stems from woolly thinking on my part, namley, in erroniously imagining that evolution is about optimising a creature's form to fit a place. The more I've thought about the moss examples above however, the clearer it seems to me now that it is not 'body shape' that evolution is working to optimise, but rather the whole organism. That is, not merely its shape and colour, but rather the totality of its life cycle and survival strategy. Furthermore it is not sufficient to think of a lichen's 'environment' as being merely some unchanging point in space (the surface of a twig, say). This misses the very significant additional fact that our twig is subject to an annual cycle of dramatically changing seasons and that it itself is a growing, changing, transitory thing. At the risk of sounding too poetical, thinking of the lichens on my tree now I begin to get an image of a complex spaghetti of life histories and strategies at work. It is facile to try to ask whether 'yellow and flaky' is a 'better or worse' body shape for living on twigs than 'flat and grey'. Instead, each lichen will be following some complex survival strategy with multiple factors and tradeoffs. Viewed in this way, although two lichens have met on a twig in photo 1, viewed over extended time, the 'trajectory' of their lives is no doubt entirely different. The forms they have will be because these are the forms that best befit them to their individual, distinct, extended, life styles.

My great pleasure in researching this blog is that through it my view of my garden grows richer all the time. To my mind, no one has said it beter than Martin Luther

For in the true nature of things, if we rightly consider, every green tree is far more glorious than if it were made of gold and silver.

An Ichneumon wasp - Amblyteles armatorius

2010-09-11T08:25:00.019+01:00

I am an amateur naturalist trying to learn something about everything living in my garden.

Hello! After a goodly absence I am back with some more of my garden wildlife. I hope there may be one or two of you out there still reading. Certainly my garden has not run short of new lifeforms to offer. Despite over a 100-species blogged so far, I have a long backlog of additional finds with more turning up all the time.

Photo 1 shows a magnificent insect I spotted resting on my hedge in late-summer of last year. The body was around a cm in length. Based on some similar images on the web I'm identifying it as an Ichneumon wasp - Amblyteles armatorius.

With tens-of-thousands of species of Ichneumon wasp worldwide and about 3200 in Britain alone, definitively identifying Ichneumons is a job for the specialist. Dr Gavin Broad is one such and has helpfully made available an online British checklist and a key to the sub-families of Ichneumonidae. You can download the entire 380-odd pages of the 1903-published Ichneumonologia Brittanica for free here. For any naturalist willing to grapple with the subject however, a supreme example of what can be achieved (and surely a candidate for "all-time greatest garden study") is given by Jennifer Owen. Her book, The Ecology of a Garden (Cambridge Uni. Press) records 15 years of painstaking cataloguing of the wildlife in a UK garden. During her studies Dr Owen discovered no fewer than 529 species of Ichneumon of which 15 were new to Britain and a staggering 4 were new to science!

From the comments above it will be understood my amateur's identification, based on a photograph alone, of my wasp as A. armatorius is to be treated with caution. It is certainly not the only European black -and-yellow striped Ichneumon as can be seen, for example, from the photo's here of species such as Ichneumon stramentor, I. xanthorius, Eutanyacra crispatoria and Diphyus quadripunctarius. For now I'm sticking with A. armatorius, as some of these others have yellow-striped antennae and other small differences, but I'm happy to be corrected by any of the experts out there.

Sadly, I have been able to uncover rather few details of the natural history of my Ichneumon. I have learnt that it is fairly common in the UK and the sole species in the genus Amblyteles. Adults apparently feed on pollen, that of umbellifers being a common target. In common with many other ichneumon's, the larvae are parasites of caterpillars, one target moth being The Yellow Underwing (Noctua pronuba). The larvae hatch inside the caterpillar and devour it from the inside. Other target moth species besides the Yellow Underwing are variously stated for A. armatorius. The scientific paper by Rolf Hinz (Entomofauna, 6(8), 1985, pp.73-77) disputes these claims however.

The paper above is in German incidentally, which is unfortunate if like me, you don't speak the language! (I found a free online copy of this paper some time ago, but have entirely failed to relocate it since. Anyone?). Since this was one of the very few learned articles I came across on A. armatorius however, I was determined not to be put off and came up with the idea of running the German text through Google's free, online automatic translation service. The results of computer translation are not always transparent. A German sentence that, in the original, I take to say something along the lines:
"I'm grateful to Messrs. G. and E. MannBausch Heidt of the Künanz Upland Bird-research Centre for supplying me with specimens"
gets translated as
"Messrs. G. and E. Mann Bausch Heidt from the research Künanz bird-house in the mountain, the procurement of the material allowed, thanks."
Nevertheless, with patience it's generally possible to get the gist and I'll certainly consider using this approach in future.

I appear to have digressed! When starting today's posting it had been my intention to say something on the amusing topic of the religious debate sparked amongst Victorians naturalisists by the life-style of the Ichneumonidae. Since I have written enough for now however, and since, with another 3000-odd British Ichneumonidae out there, I feel confident I will have other chances to revisit this fascinating family of insects in the future, I will leave my somewhat cryptic last sentence hanging in the air and bid you farewell for now.

Two Prominent Moths

2010-05-07T21:29:00.043+01:00

I am an amateur naturalist trying to identify everything living in my garden.

Some time ago I blogged the moth trap I was constructing. My first design was only partially successful (most of my catch were escaping!) and since then my designs have undergo a number of iterations to finally arrive at The Walloon Super Trap you see before you in photo 1! I'm pleased with this design. In fact, the only problem is that the few times I've put it out in my garden it has yielded such a bumper catch of night-time insects I now have a long backlog awaiting a write up on this blog.

Anyway, on to the stars of today's posting. Photos 1 and 2 show two moths trapped (for the record) on 25th and 22nd April 2009 respectively (I let them go after I'd taken their photos).

A little time spent with my copy of Field Guide to Moths (Waring, Townsend) and I was able to identify the first as a Lesser Swallow Prominent (Pheosia gnoma) and the second as a Coxcomb Prominent (Ptilodon capucina). I'm guessing the various points and fluffy quiffs on my moths are there to resemble thorns and to break up the moths' outline when resting on branches.

The Lesser Swallow Prominent is superficially similar in appearance to the Swallow Prominent (Pheosia tremula) but the neat white triangle on the upper part of the wing identifies my moth as the former. The caterpillars feed on Birch and the book tells me it is fairly common in the UK.

The Coxcomb is also common. Its larvae feed on a variety of trees including birch, hazel and hawthorn.

My moths are both members of the Notodontidae family of moths of which 27 species have been recorded in Britain (there are several thousand worldwide). My attempts to learn something of them led me to some fascinating online papers about the sense of hearing in moths.

It turns out the Notodontidae moths are notable for having some of the simplest ears of any insect. To we humans, insects wear their ears in rather strange positions - sometimes on the legs, sometimes the thorax and even (in the case of some lacewings) on the wings. This paper by Yager gives a review.

Insect ears broadly follow a common design. A thin membranous 'ear drum' (the tympanal membrane) vibrates in response to sound and the vibrations are detected by structures called scolopidia that are basically stretch receptors. The scolpidia detect movements of the membrane and fire off signals down a connecting nerve. Some grasshoppers have around 2,000 scolopidia. Notodontid moths are at the other extreme with only one.

Yager's paper above quotes the remarkable figure of 1 Angstrom (=a ten-millionth of a millimetre) as the smallest vibration of the membrane that insect ears can detect. If true, I find this truely incredible as 1 Angstrom is about the diameter of a single atom!

I did not manage to find any freely available references to the hearing specifically of my moths, but I have come close with a paper by Annemarie Skurlykke on the hearing of the Swallow Prominent (you'll recall my moth above is the Lesser Swallow Prominent). From this I learn that the Swallow Prominent hears best at frequencies around 60kHz. For perspective, the highest note an adult human can hear is said typically to be around 20kHz. Why should moths be sensitive to such high ('ultrasonic') frequencies? The answer can be summed up succinctly: Bats! Bats are prodigious predators of night flying insects and hunt by echolocation using ultrasound.

I came across a couple of interesting online review articles (by Ratcliffe et.al. and another by Miller and Surlykke) describing how moths and other insects react to hearing an approaching moth. It seems that many moths react in two stages. If the bat is some distance away the moth simply flies away from the sound of the echolocating bat. If the bat gets close enough to strike however, the moth takes more dramatic action such as spiralling in flight or even folding its wings and dropping out of the air. How moths are able to determine the range of the bat isn't fully understood. Bats reduce the time between their ultrasonic squeaks as they get near to striking an insect however in order to better 'see' their prey, and the suggestion is that the moths are sensitive to this increase in squeak-rate. Regardless of how they do it the defence seems fairly successful with those species of moth capable of hearing and reacting to bats improve their survival chances by some 40%.

Of course moths do not get everything their own way. Firstly, diving to the ground is fine...unless (as Guigon and Fullard explain) the 'ground' turns out to be water! Naturally also the bats are not about to take things lying down and have evolved a number of strategies to bypass the moths' defences. Some appear to have adopted frequencies above or below the range of moths' hearing and others may rely to a significant extent on simply seeing (visually) or listening for their prey. Ultimately however, as Miller and Surlykke comment "some barbastelle bats prey almost exclusively on tympanate moths, and just how they do this is not known". Another of nature's puzzles!

A signalling fly Poecilobothrus nobilitatus

2010-04-24T12:48:00.051+01:00

I am an amateur naturalist trying to learn something about everything living in my garden.

I have a plastic tub in my garden that has become partly filled with rainwater. Passing it last summer, my attention was caught by some flies busying themselves at the water's edge. A closer look revealed some fascinating behaviour: the wings of my flies were characteristically marked and the flies were solemnly raising and lowering them just as might an airport worker guiding a plane to a parking spot with a pair of semaphore flags.

I took some photo's though I confess I rather expected to fail to identify my fly. There are so many species (more than 15,000 in Europe) that to identify an unknown fly can be a tall order unless you're willing to spend hours with a magnifying glass and have access to some serious, specialist literature. Fortunately however, it turned out my fly is not uncommon, its behaviour having been noted by a fair few people, and an internet search led me to the species name: Poecilobothrus nobilitatus.

The stately wing-spreading displays of my fly are part its courtship display. As everyone knows, courtship displays are very widespread in the animal kingdom and can be fantastically intricate (one need only think of peacocks or the dance of Great Crested Grebes (video here)) . It's very natural to wonder what purpose such displays serve. Vast amounts of literature exist on this topic, with a great many unknowns and disputed theories. I don't have anything like the knowledge to comment expertly. My blog is about my learning something of my garden's natural history however, so a few facts gathered from some general reading on my part seem in order:

According to my copy of An Introduction to Behavioural Ecology (Krebs and Davies), the modern view is that, at the deepest level, courtship arises from a conflict between males and females over scarce resources. The point is that sperm are small and energetically 'cheap' to produce. Eggs, however, are larger and energetically more costly to produce and gestate. In the jargon, eggs are a scarce resource. Since eggs are, in this sense 'expensive, high value objects' it is worth males investing effort and energy competing for them. Equally, for females it pays to be 'choosy' when it comes to 'cashing in' the energy investment an egg represents.

The argument above might seem rather abstract, but its consequences are deep. Take the issue of mating with a wrong species: Some species of fruit flies for example, can and sometimes do, interbreed. Often this inter-species breeding results in sterile offspring however. From the perspective above, such parents have wasted precious time and energy. Clearly, it would have benefited them to have had some way to accurately check a prospective partner's species prior to mating. The elaborate courtship dances of some fly species (see here for example) may be just this: a way for females to check whether a male is of the correct species. From the female viewpoint, this avoids wasted energy on improper fertilization of her 'expensive' eggs. From the male point of view, although dancing costs him some energy, eggs are a scarce resource and having found some (i.e. a fertile female) it is worth the investment.

To take a second instance: Since eggs are a scarce resource it is important to lay them somewhere safe and where there is enough food available for the hatchlings. Some courtship displays - such as those where a male presents a female with some 'gift' (say, a morsel of food or a beak-full of nesting material) may be a way for the sexes to share the energetic cost of laying in a particular location (the female pays the cost of depositing her precious eggs; the male pays the cost of finding and presenting a 'courtship gift' that proves the location's suitability).

Yet another purpose of a courtship display may for females to test whether a male is a fit, strong individual, and able to pass on good genes to the egg. Actually, one needs to be a little careful before asserting a given courtship display is about a male demonstrating genetic fitness. To see why, imagine a species of bird that shows-off some glossy plumage during courtship. To say the male is demonstrating genetic fitness, makes an assumption that there exists an (inheritable) gene for glossy plumage for that bird. There may be, but on the other hand there may not. It could be that a male's glossy feathers are nothing to do with his genes but are due to him having been living somewhere that allowed him a good a plentiful food supply. The fact that females are choosing glossy feathers may be nothing (or perhaps only indirectly) to do with a male's genes, but because they say: "Food here is plentiful. It's a good place to breed". The point is not that advertising 'good genes' can never be a reason for a courtship display, simply that one cannot take it for granted as an explanation.

Anyway, in summary, a modern view is that courtship is about competition for resources between males and females. The successful male gets the benefit of the female's energy investment in eggs. In return females get an energy expenditure (=courtship display) from a male that relays something of benefit such as 'this is a good place to lay', or 'the male before you is the correct species', or 'the male before you has 'good' genes', or...(there are lots of other scenarios).

This barely makes a dent on a vast subject of course, and a great deal more could be written on the theory of courtship. This isn't the place to do it however, and instead let's get back to talking specifically about the my fly P. nobilitatus:

The best freely available online paper about my fly I came across was that of Zimmer, Diestelhorst and Lunau which describes the courtship behaviours of eight, so-called 'long legged flies' (Dolichopodidae), mine included. A number of these flies carry display 'badges' they use in courtship. Liancalus virens for example, also has signalling spots on its wings (see picture here). Neurigona quadrifasciata (here) uses foot markings to signal to females.

The paper provides a number of interesting facts about my fly. Firstly, experiments show that male wing span is directly proportional to body size: males with a big thorax also have big wing spans. During courtship P. nobilitatus males work to keep at a constant distance of 2.5cm from females. Taking these facts together, a plausible hypothesis is that female P. nobilitatus flies consider male body size important (as an indicator of a male's health status perhaps). By this argument the male's wing badges and constant- separation-dance are present in order to help females accurately estimate the body size of their suitor by sight.

Another intriguing suggestion in the paper is that males may have evolved signalling 'badges' to allow them to mate on the ground. The idea is this: some species of flies court in flight with males performing aerial stunts or hovering. Presumably these difficult and energetic winged manoeuvres may again allow females to assess health by looking at, say, wingspan. Now, suppose a male could 'con' a female's reproductive senses into thinking she was being presented with a hovering male when in fact both were sat firmly on the ground?! This is not as implausible as it sounds when we remember we are talking about a little fly whose intelligence and eyesight are not necessarily great! The female's reproductive senses may detect the 'beating' wings of a hovering male simply by whether her eyes detect (say) the outline of a wing and certain patterns of light and dark in the space before her. If a male could replicate these patterns whilst still on the ground, he might be able to fool the female's senses into a mating response, and at the same time save himself from the energetically costly business of hovering. The technical term for such cheating is 'sexual mimicry'. The paper concedes that this idea remains unproven for the long legged flies. I hope you'll agree however it's fascinating stuff and it all goes to show just how incredibly rich and intricate are the patterns of life just outside our front doors.

Lady's Smock Cardamine pratensis

2010-03-20T13:29:00.032Z

I am an amateur naturalist trying to learn something about everything living in my garden.

Photo 1 shows an attractive flower I found growing wild in a neglected corner of my garden early last summer.

A little time spent with my trusty copy of The Wildflower Key (Francis Rose) and I'm fairly confident my plant is Lady's Smock. The leaves of my plant are also rather characteristic (photo 2) with the lower leaves tending towards round with the largest leaf being the one furthest from the stem, whilst the upper leaves are rather long and narrow.

My copy of The Englishman's Flora (Geoffrey Grigson) lists around thirty alternative common names for Lady's Smock from the pretty Cuckoo Bread, Cuckoo flower, Lucy Locket and Milking Maids to the less flattering Pig's Eyes and Bog Spink!

The scientific name for my flower is Cardamine pratensis. Pratensis is from the Latin 'of meadows'. From some web searching I understand Cardamine owes its heritage to the anicent Greek physician Dioscorides (ca. 50AD) who used the name for some cress-like plants, karda being Greek for 'heart', and damao to 'tame or overpower'. (I've read that Lady's Smock is an edible, spicy, salad leaf, though I can't vouch for the truth of this.)

Lady's Smock is a favoured food of the caterpillars of the Orange Tip butterfly.

C. pratensis is a perennial, native to the British Isles and is highly variable. The paper here gives a flavour of the lengths the professionals have gone to in attempting to characterise it. My copy of New Flora of the British Isles (Stace) sums things up rather bluntly however as "impossible to subdivide usefully; identity of [named] variants [...] is very dubious". My attempt to get some basic amateur understanding of the issue led me into a study of polyploidy. I'm certainly no expert on genetics but briefly my understanding is this:

As most people know, at times the DNA inside living cells gets packaged into structural units, the chromosomes. A microscope reveals we have 46 chromosomes. Closer investigation reveals that these 46 are in fact present as two largely similar sets of 23 i.e. 23 chromosomes from our mother and a similar 23 from our father. (The phrase 'largely similar' skips over a wealth of detail, such as the fact that a certain chromosome from our mother might carry a different characteristic, say eye colour, to that from our father etc. - but never mind that here) . For humans we say "2n=46". Other mammals have other chromosome counts, for example I read variously on the web that the kangaroo has a mere 2n=12 whilst the European hedgehog boasts 2n=88 (in general there is no link between chromosome number and the size or complexity of a creature).

In the case of many plants, a lesser number of insects, amphibians, fish and a very few mammals (one being an Argentinian Plains Rat - see the parade of polyploids here!) however, things are more complicated. Some varieties of strawberry for example contain not, as we humans, two largely similar sets of 23 chromosomes but no fewer than eight sets of seven chromosomes. This gets written as "8x=56". This condition of having more than two sets of chromosomes is termed polyploidy.

The fact that more than 30% of plants go in for polyploidy would seem to indicate it must have some important benefits. There are many theories as to what these benfits might be. It's been suggested for example, that polyploidy may promote greater variation in a species and thereby help it evolve ('radiate') more easily into new environments, or that polyploidy may provide protection against 'in-breeding' issues that might otherwise arise for plants that self-fertilise. It seems also that some polyploids are healthier and more vigorous than non-polyploids. In all however, there seems to be no universally accepted theory of why so many plants are polyploids. Another of nature's mysteries!

Anyway, all of this preamble basically allows me to comment that my garden weed occurs in a bewildering variety of genetic 'forms' from the 'diploid' 2n(=2x)=16 through types with chromosomes numbers of 14, 15, 16, 19, 20, 21 – 28, 30, 32, 37, 42, 44, 45 and 48.

After the science, who better to have the last word than the Bard. From the song 'Spring' at the end of Love's Labour's Lost:

When daisies pied and violets blue,
And lady-smocks all silver white,
And cuckoo-buds of yellow hue
Do paint the meadows with delight,

Painted Lady Butterfly Vanessa (Cynthia) cardui

2010-03-07T10:21:00.040Z

I am an amateur naturalist trying to learn something about everything living in my garden.

Photo 1, taken back in late Summer, shows a Painted Lady butterfly enjoying a well-earned rest on a leaf in my garden. I say 'well earned' as this butterfly will likely have undergone an amazing 1000 mile migration, to arrive in my garden from North Africa.

The entire British population of Painted Ladies (Ladys?) arrives here in Spring and leaves again in Autumn (strictly not all leave, but those that don't fail to survive the British winter).

To have encountered a Painted Lady in my garden last Summer is perhaps unremarkable when you learn that 2009 was a mass migration year for Painted Ladies to the UK. Millions arrived, with one flutter (the collective noun for butterflies) alone of 18,000 spotted off the South Coast of England.

A fun thing to know (who knows, it may help you win a pub quiz one day!) is that the Painted Lady is the only species of butterfly recorded from Iceland. I got this fact from the admirable UK Butterflies site, which contains numerous facts and photos about the lifestyle and food preferences of the Painted Lady that I'll not reiterate here. Suffice to say that caterpillars of the Painted Lady are dark and hairy and feed on thistles and nettles.

My searches for information on my butterfly were complicated by the fact that some sources seem to use the Latin name Vanessa cardui, others Cynthia cardui, and still others talk about the species cardui in the genus Vanessa and sub-genus Cynthia. I've not had a chance to sort out which is the professionally accepted name. Anyone?

Another topic my searches led me to was the (new for me) subject of 'foraging theory'. This is a huge topic and the reader should be take my (decidedly amateur) understanding and description with a 'health warning'. Briefly however my understanding goes like this: We've all watched bees and butterflies drifting through patches of flowers, or watched little songbirds working their way through the tree tops pecking at tidbits. Perhaps, like me, you've never really noticed any particular pattern or method to the foraging of these animal. At a glance, butterflies for example, seem to drift along haphazardly, landing on any such plant as they encounter and (one might presume) staying there for as long as it takes to drink a flower's nectar dry. In fact, many years of fabulously detailed studies by armies of biologists have shown that the foraging practices of many animals are anything but random. Quite the contrary, foraging animals have evolved highly specific methods and rhythms, carefully fine tuned to allow them to optimally gather food from their environments.

A classic example of decidedly non-random foraging was revealed by the studies by Messrs. Richardson and Verbeek (you can find one of their papers here) on the feeding habits of a population of crows in British Columbia. The crows were foraging on a beach for clams. Now, you might naively assume that a crow would simply gobble up any clam it came across. This fails to take account of the fact however, that a crow has first to open up a clam's shell in order to get at the meat inside. Now, little clams don't take much time and energy to open...but then, they don't yield much meat either. Huge clams yield lots meat...but they require the crow to spend a lot of time and energy to get them open. From this you start to realise that if a crow is to get the maximum food benefit from an hour (say) spent feeding, there will be some optimal clam size the crow should target in order to spend the least time for the most meat. Amazingly, this is what the studies showed: the crows were selecting just those sizes of clam that allowed them to maximise their average energy intake.

Similar studies have been replicated across many animals with the same results: crabs show optimised strategies similar to those of crows when selecting the size of mussels to open and eat; studies on brooding starlings show that parent starlings will continue to hunt for worms in the field until they are have just the number of worms held in their beaks that optimises the bird's efficiency in getting to and from the nest (Carry too few worms and the parents must make too many energy-sapping flights back and forth to feed the chicks. On the other hand, spending too long in the field trying to peck up worms with a beak already stuffed full is slow and cumbersome and results in the parent trying to carry an excessively heavy load back to the nest); Male Yellow dung flies show behaviour that optimises the balance of time and energy spent feeding vs. the time and energy spent in moving between dung heaps looking for females with which to mate.

Actually, although foraging behaviour can be discussed using words as above, in using phrases such as ' the maximum energy acquired per unit time' etc. the numerically minded amongst you may start to realise we are approaching the possibility of a mathematical desciption of foraging ( time-rates-of-change of quantities are the 'bread and butter' of the calculus you may recall from school). A mathematical description of foraging is just what the professional biological community has developed. The classic textbook Foraging Theory by Stephens and Krebs, gives a flavour.

Some of the seminal early work on foraging was by Charnov in 1970's. Charnov developed an important theorem known as the marginal value theorem which dealt with the situation of an animal foraging between patches of food spaced some distance apart (separated patches of flowers in a meadow for example). The question is, how long should a feeder spend in any given patch before moving on? Spend too long in one patch and the available food dwindles away (the animal is reduced to hunting around for the few remaining 'scraps' so to speak). Equally it takes time and energy to fly between patches. Charnov's theory was developed to predict the optimal time an animal should remain in any one patch in order to maximise its average rate of energy intake (or to put it another way, the foraging pattern resulting in the animal getting, on average, the most calories per hour).

All of which preamble, brings me back to the Painted Lady and the papers I came across by F.R. Hainsworth. Hainsworth studied whether Painted Ladies follow the predictions of the marginal value theorem. Specifically he studied how Painted Ladies reacted to being offered sugar-water solutions of varying strengths. Should Painted Ladies be following the predictions of the marginal value theorem then they should preferentially feed on those sugar solutions that would allow them to take up, on average, the most energy per hour. Now, a crow having to wrestle with opening a clam shell or a fly having to divide its precious time between feeding and mating is one thing. But you may wonder what's to stop a butterfly simply opting to feed on the most sugary solution offered every time? The answer is satisfyingly subtle: you must remember that a butterfly is constrained to having to feed through a straw! (The proboscis). If you imagine yourself being hungry but constrained to eat through a straw, you'll realise that whilst a thick gloopy syrup will certainly provide you more total energy than a thin watery one, sucking a jar of treacle through a straw is certainly no quick meal! When you realise this, an answer to the question of what sugar concentration in water will allow you to imbibe the most calories per hour is suddenly not so obvious.

I can't help but digress at this point to briefly address the question: How do you gather data on the feeding preferences of a butterfly? One option is to chase your specimen around a forest with a stopwatch! Preferable of course, is to find some way to get a captive butterfly to eat 'on demand' in the laboratory. This might sound tricky but Hawksworth provides a wonderfully simple solution that any suitably motivated amateur could replicate (naturally, you need a supply of butterflies but there are various companies on the web that will sell you eggs and caterpillars). The trick is to know that butterflies can taste through their feet! Gently hold your butterfly between thumb and finger, lower its feet into a dish of sugar water and, bingo!, it will instinctively unroll its proboscis and begin to feed. Get yourself a stopwatch and you're all ready to test the marginal value theorem!

Anyway to return to our main question: Are the eating habits of Painted Lady's in agreement with the marginal value theorem, with butterflies eating so as to maximise their average rate of energy uptake? Interestingly, the answer seems to be no. Instead, Painted Ladies go for meals that give them the most energy in one sitting (even though it may take longer to eat such a meal). This doesn't mean the marginal value theorem is 'wrong' (as above, it applies well in some situations), it simply means that one or more of the assumptions upon which this theorem is based don't apply to the Painted Lady. One suggestion is that rather than playing the 'long game' of choosing sugar solutions that maximise the calorie intake over a long period of time, newly emerged female butterflies are keen to pack in high calorie meals early, in order that they can quickly take on board enough energy to enable them to lay a large clutch of eggs. Whether this is the full story however appears to require more study...but then of course, you, dear reader, now know how to approach the task of conducting butterfly feeding experiments. I'm entirely confident therefore, that the answers will be with us shortly!

Helophilus pendulus hoverflies

2010-03-06T09:50:00.024Z

I am an amateur naturalist trying to learn something about everything living in my garden.

Photo 1, taken back in September, shows two mating hoverflies resting on a leaf of my garden Buddleja bush. The characteristic brown stripes on the thorax quickly let me identify the species as Helophilus pendulus in my copy Hoverflies (Francis Gilbert, Richmond Publishing), an excellent monograph I've talked about before.

I assume the pair in photo 1 is male and female. Apparently it's normally possible to tell the two sexes apart in hoverflies by the eyes: The eyes of males touch at the top of the head, whereas those of females don't. Unfortunately this isn't true of Helophilus species. Why, generally, hoverfly sexes should differ in this regard, and specifically why they don't in Helophilus species, I can't imagine. Can anyone comment?

As I've mentioned previously, it's possible to distinguish hoverflies ('Syrphinae') from other flies by the veinature of the wings. In photo 2 I've zoomed in and enhanced the shot with my camera's software. Hoverfly wings have a 'false vein' (running approximately vertical in photo 2) and a section of vein at the edge of the wing that other flies lack.

In The Encyclopedia of Land Invertebrate Behaviour, the authors, R&K Preston-Mafham, describe male H. pendulus hoverflies as searching near flowers for females but often pouncing on other species of fly by mistake.

My copy of The Colour Guide to Hoverfly Larvae (G. Rotheray, Dipterists Digest 9) explains that the larvae of H. Pendulus thrive in farmyard drains and wet manure. Nice! My web searches also turned up a paper by one E. Stanley in the Veterinary Record 1845, 1(4) that describes finding an H. Pendulus maggot infesting the spinal marrow of a horse. By appearance they are a dark brown maggot with a tail as long as the body that acts as a breathing tube.

An obvious feature of hoverflies is the resemblance of many species to wasps and bees. Indeed, as explained in the extensive and very readable paper The Evolution of Imperfect Mimicry in Hoverflies by Francis Gilbert, at least a quarter of European hoverflies are mimics. Clearly, the mimicry is simply a matter of hoverflies trying to fool birds into thinking they are a wasp that will sting them....right? Well no actually, or at least it can be said the situation is far more subtle. As the paper above highlights the subject of animal mimicry is a complex one, much studied by biologists, and a topic where numerous questions and controversies persist.

Firstly, one should not assume that the 'warning colours' of hoverflies are, in all cases, a response to the threat of bird predation. There are plenty of other animals such as dragon flies, wasps and spiders will also eat hoverflies. Spiders have been shown to have an ability to recognise the threat posed by wasps in their web, and to treat them with greater caution than they do with other insects. At the same time, some experienced birds such as Flycatchers have been shown to be rather skilled at 'seeing through' the disguise of hoverflies - readily distinguishing them from wasps.

Next there is the issue of whether what we, with our human eyes, see as a resemblance to a wasp, is the same as what a predator perceives with eyes that might have very different characteristics to our own (different colour sensitivity etc.) Experiments studying the willingness of pigeons to peck at images of various hoverflies and wasps have shown that pigeons do broadly rank resemblances of hoverflies to wasps in the same way that we do. But there are exceptions with pigeons regarding Syrphus ribesii as the most wasp-like hoverfly of all, a view not shared by humans.

Next, there is the question of whether it is a bee's or wasp's sting that a predator is avoiding and that a hoverfly is "pretending" to posses. In fact, it seems that birds hardly ever suffer wasp stings and actually it is the unpleasant taste of a wasp's internal venom sack that some birds avoid. With Bumblebees (which some hoverflies mimic) the situation is more subtle still. There is some evidence that the sheer effort (in terms of wasted time and energy) involved in removing all the various hairs and largely inedible, chitinous, 'body armour' of a bumblebee is enough to put off some birds. Contrary to proclaiming its sting, the colouration of bumblebees (and their hoverfly mimics) may be a way of saying "I'm not worth the time and calories you'll get from eating me!".

This brings us to the difference between so-called Batesian mimicry and Mullerian mimicry. Batesian mimincry is the type of mimicry most of us imagine at first, whereby a harmless insect species evolves to copy the warning colours of a harmful one. By contrast, Mullerian mimicry involves two or more species that each have defences of their own, but nevertheless carry a common warning colour or form. Lots of bees and wasps all have yellow stripes for example. One can understand how this might arise: Suppose a predator has a bad experience with a harmful species. If that predator comes to associate the bad experience with a warning marking for that one species (yellow stripes say), then there's clearly potential benefit in other poisonous species adopting similar markings. By adopting similar markings however, one wasp species is not really 'copying' another, rather, both species are gaining benefit by evolving in parallel to advertise their venomous natures through similar body markings (multiple species settling on a 'common format' for advertising their individual danger signals if you will) . Now, in saying that hoverflies 'copy' wasps we are making the tacit assumption that hoverflies are harmless Batesian mimics. This is probably mostly the case. But it need not be universal. For example, it has been suggested that some species of hoverfly concentrate unpleasant tasting chemicals in their bodies through eating aphids that have been feeding on noxious plants. Such hoverflies would have their own defences (their noxious taste) and any evolved resemblance to say wasps, might then be an example of Mullerian mimicry.

The list of fascinating questions surrounding mimicry goes on. There is the question of the drawbacks of mimicry. Naively, it might seem there could little detriment for a species in 'wearing the clothes' of another. But suppose the venomous species being copied becomes rare. If a non-venomous hoverfly were to become more common than a venomous bee (say) it might be copying, what then? Predators would rarely (or even never) meet with the bad experience of finding that the prey in their mouth was the truly venomous one. After a time predators might simply stop associating the mimic's bright colours with danger. Indeed, the bright colours of the hoverfly mimic might become a positive liability, gaudily advertising the presence of a tasty snack! In summary, by choosing to copy the colours of another species, a mimic pays the price of shackling its population size that of the target insect being copied. Exactly the nature of the constraint (i.e. the mathematical relationship between the sustainable population of the mimic vs. the copied species) is a rich topic in its own right.

I could go on still further into a discussion of polymorphism in mimics, whereby a single species of say, hoverfly, comes in a number of different (colour) forms called morphs, and the benefits this confers. I've written enough for now however and so will leave this topic for another day, or, if you cannot wait for then, refer you to the paper above by Gilbert.

A lichen Aspicilia contorta

2010-02-21T09:40:00.027Z

I am an amatuer naturalist trying to learn something about everything living in my garden.

Returning to the iron manhole cover I discussed in my last posting, photo 1 shows yet another lichen eking out a living on the metal surface. From my copy of Lichens (F. Dobson, Richmond Publishing) I'm fairly confident the lichen here is Aspicilia contorta.

The little 'volcanoes' I've marked in the picture are the lichen's spore producing fruits (apothecia). If you're trying to identify a species of a lichen it's worth knowing that apothecia come in different 'flavours', in particular lecideine and lecanorine apothecia. This is well covered in the text books, but I wasn't able to readily locate a picture on the web so I've drawn one myself (I'm no botanical illustrator as you can see!). The difference is in the margin of the fruit body: The margins of lecanorine lichen apothecia tend to be the same colour as the main underlying lichen body (thallus) and contain algae. By contrst, the margins of fruits of lecideine lichens tend to appear distinct from the thallus and do not contain algae. The latter are often black (the books sometimes refer to the margin being 'carbonised'. I don't know whether this is just poor terminology or whether the lichen really does manufacture something akin to raw carbon in the margin. Anyone?).

From the description above it will be clear Aspicilia contorta is a lecanorine lichen.

Actually, my efforts to track down a description of all this on web led me to encounter a fair amount of technical jargon surrounding apothecia that had me quite confused at first. To save any fellow interested amateurs out there the trouble of going through the same, drawing two and the description below summarises the understanding I managed to pick up.

As I'd understood from my previous experiments slicing up apothecia, lichen fuits comprise an array of asci (= little tubes filled with spores). Photo 2 shows a single ascus I managed to separate from an apothecium I took from my garden A. contorta. As shown in drawing 2, the asci come sandwiched amidts a mass of upright fungal threads ('hyphae') known as paraphyses. The specialist textbooks often include pictures of these paraphyses, as they too can help in identifying the species of a lichen.

The fact that the asci are neatly arranged in an upright position is of course, no accident. It's important to the reproductive success of the lichen that when spores exit an ascus, they do so into the open air. There would clearly be no point in having the asci oriented haphardly and liberting a substantial proportion of their spores into back into the walls of the apothecium from where they've arisen in the first place. Of course, this only explains why the asci stand upright, it doesn't explain how they know which way is 'up'. I was fascinated to learn recently however (from a copy of the classic Spore Discharge in Landplants (Ingold) that I was lucky enough to find in a secondhand bookshop) that many cup fungi are phototropic (= sensitive to the direction of daylight), and use this to beneficially orient themselves. The book describes this for various cup-fungi, and I assume it is also the mechanism used by lichens, though strictly, I haven't come across a reference to confirm this (anyone?).

The asci + paraphyses are arranged on a thin layer known as the hypothecium. This comprises a mass of dikaryotic fungal cells, each containing two DNA nuclei. By a complex process of chromosome divison (mitosis) these cells eventually form (single nucleus-) spores. The whole business of sexual reproduction in lichens is complex and there is probably a lot left to discover. The pdf document here has some details.

The outer part of the fruit (technically termed the excipulum) comprises a mass of single-DNA-nucleus (haploid) fungal cells.

So now you know!

Today's has been a rather technical posting and perhaps marks a suitable point to leave my garden's lichens for a while (though I have yet to exhaust them). Outside the first signs of Spring are here: The volume of birdsong is increasing as the breeding season approaches and today on a country walk I spotted my first ladybird of the year (despite Oxfordshire still suffering regular frosts at night), all of which suggests I will not have to look too hard for new signs of life in my garden. Until next time...

A lichen Lecanora dispersa

2010-01-30T09:51:00.030Z

I am an amateur naturalist trying to discover everything living in my garden.

I have a manhole cover in my garden. (Try to contain your excitement at hearing this news dear reader!) This may seem an unpromising place to search for life, but a closer look reveals a host of those most enterprising (in terms of the habitats they are willing to conquer) of creatures - the lichens.

Zooming in, photo 1 (click on photos to enlarge) reveals at least two species: The yellow lichen (which looks like our old friend Caloplaca citrina - though I've not taken time to carefully check this) and a second species with numerous white, frosted fruits ('apothecia').

A little time spent with my trusty copy of Lichens (Frank Dobson, Richmond Publishing) and browsing some similar images on the internet, and I'm tolerably confident the latter is the lichen Lecanora dispersa.

There are at least 20 British species of Lecanora lichen. Dobson describes L.dispersa as 'very common and found even in the centres of cities'. It will grow on a variety of basic substrates including bark, stone, iron and leather.

Photo 3 shows a magnified view of the apothecia, with their white, wrinkled rims.

For photo 4 I took one apothecium and made a squash between a microscope slide and a coverslip. As I've discussed previously, lichens are a partnership between fungi and algae. The small green, algal cells are clearly seen in photo 4. That algae can be present throughout a lichen's cup-shaped apothecia was a new discovery for me - I'd hitherto only associated them with the non-fruit parts of a lichen.

The main purpose of a lichen's apothecia is to act as surfaces from which to liberate numerous reproductive spores. I've talked about this before, but I was not previously in a position to complement my descriptions with photographs. Recently however, I've been lucky enough to come into possession of a Cambridge rocking microtome. For those unfamiliar, this is a device for taking extremely thin (~few microns) slices of a specimen, which can then be viewed under a microscope. Actually things are not entirely straightforward, since, in order to avoid said slice ripping and disintegrating as it's cut, it's necessary to first provide support to the cellular structure of the sample by embedding the whole thing in a block of wax. The recipe for doing this is a little involved: Starting from pure water, you pass the sample through half-a- dozen water+alcohol baths. The baths are arranged so that the alcohol concentration steadily increases until finally your sample is left sitting in pure alcohol, the water in the sample's cells having, by then, been replaced with alcohol. Next, you substitute the alcohol for the solvent toluene (a solvent of wax) before dropping it into a bath of molten paraffin wax and leaving for several hours. Finally, you pour the wax+sample into a mould and leave to cool. (In fact, there are still futher steps that finesse this process - but you get the general idea! Should you wish to try it yourself the best guide I've found is the booklet Practical Microscopy (Eric Marson, Northern Biological Supplies) and/or you could join one of the hobbyist microscopical societies such as the redoubtable Postal Microscopical Society.)

Photos 5 and 6 show my rocking microtome. The blue handled blade is the extremely sharp sectioning razor. The white object is the wax-block-embedded sample. Pulling the lever at the rear of the microtome (photo 5) raises the sample and releasing (photo 6) forces it down onto the blade shaving off a wafer thin slice and simultaneously ratcheting the sample forward ready to take the next.

And the consequence of all this labor?... Photo 7 shows a cross section through a lichen apothecium. Strictly, for this posting it ought to be that of L.dispersa, but working on the principle 'walk before you can run!' I instead sectioned a sample of our old friend X.parietina from my apple tree, since the latter has large apoethecia and a robust surrounding thallus (= 'body'). I've labelled up photo 7 (click to enlarge) and you can clearly see that the apothecium surface (technically termed the hymenium) comprises an assemblage of sausage-shaped 'asci' packed full of spores.

One thing puzzles me: I have not seen the granular bodies I see here labelled up in the handful of books I have on lichen. Possibly these are air bubbles. They turned up very frequently in my samples however and I don't believe they are. Can anyone comment?

Jurassic sea creatures

2010-01-23T16:02:00.042Z

I am an amateur naturalist trying to identify everything living in my garden.

Hello, and welcome to my 100th creature posting!

I started my blog three years ago almost to the day. My motivation then as now, was simple curiosity. When I began I was almost completely ignorant of the identity of many of the insects, plants, mosses and lichens in my garden.I wanted to learn a little more. I am still learning! It has been a revelation to come to realise just how rich a diversity of life there is on my doorstep, and to discover the incredible variety and subtlety of form, function and behaviour that exists just outside my window. I have encountered flies with larvae that invade the nests of bees, cup-shaped fungi that close the 'roof' in the dry weather, hoverflies that can regulate their body temperature and spiderlings whose first meal is their own mother. It has been a further revelation for me to learn what an enormously detailed body of knowledge exists regarding the natural world (sixty years' worth of data on a Scarlet Tiger moth population in a woodland in Oxfordshire; a study of the behaviour of the Greyling butterflies taking in a staggering 50,000 experimental tests; an online database of 125,000 species of algae...) and yet at the same time, what a mass of unanswered questions exist that that any sufficiently motivated amateur could answer, thereby make a lasting contribution to human knowledge. I find it an inspiration to keep looking and learning about the countryside when I read that of 265 British species of hoverfly, a staggering 40% of larvae are simply unknown (that at least was the status in 1993 according to the Colour Guide to Hoverfly Lavae, G.E.Rotheray) ; or that there are 235 sub-species of British dandelion whose distribution and ecology in the UK in only sketchily understood; or that with changing climate patterns, the amateur has every chance of spotting some immigrant creature (a ladybird, say) new to their environment.

On to today's posting. This being my centennial posting it seemed appropriate to pick something a little different, and what better than to discuss the rarest of all the creatures in my garden, so rare in fact that they have been extinct hereabouts for around 150 million years, when my garden was last a submerged mass of Jurassic oyster beds and coral reefs.

What I know about the geology of my garden I have got from reading the splendid The Geology of Oxfordshire (Philip Powell, 2005, The Dovecote Press):

For those unfamiliar with the UK, Oxfordshire is a county located towards the centre of England. Layers of strata have built up over the eons and at some point the stack of layers has been tilted, so that as you travel across the county from North to South the layer exposed at the surface beneath your feet changes from a youngest (~100 MY-old) chalk layer in the South to an oldest (~200MY-old) ironstone and clay 'lias' layer in the North. Some of these layers are softer than others and have eroded more over time, given Oxfordshire its gently undulating landscape of hills and valleys. (These are the surface-exposed rocks, were you to drill down you would hit much older rocks; 490MY-old rocks from the 'Ordovician' period are known in the neighbouring county of Buckinghamshire). The splendid people at the British Geological Survey have recently put their maps online for free viewing so you can see some of this for yourself.

The rocks in photo 1 are known as 'Wheatley Coral Rag' limestone, Wheatley being a town in Oxfordshire where they're common, although outcrops of the rocks are also found at other locations in the county including Headington (where it was extensively quarried from the 14th to the 19th century), Cowley (where, apropos of nothing, the BMW 'Mini' car is manufactured) and the hill-top village of Beckley. Probably the most magnificent example of the use of Wheatley limestone in Oxfordshire is my garden wall...although I suppose the Radcliffe Camera building (built in the 1740's) in central Oxford isn't bad either! (Photo 2 - was taken by Tom MurphyVII and I understand I can use it here under the terms of the GNU free licence). The lower 3rd of the building is the Wheatley limestone.

The material that went into making Wheatly rag was laid down in shallow seas in the Upper Jurassic period (145-161 MY-ago) when my garden would have been at a latitude of 35-40 deg. North (the latitude of Southern Spain today). The rocks are composed of masses of shards of mollusc shells, bits of sea urchin and fragments of coral. In photo 2 I've zoomed in on the rock at the rear of photo 1. I'm not a skilled photographer but I hope you get an impression of this.

I have not attempted to identify the species of my fossils. Indeed I would hardly know where to start. If one finds a fossilised Jurassic mollusc shell, is it a relatively simple matter of keying out the find from amongst a handful of known and easily distinguished species, or is exhaustive analysis needed to separate it from hundreds or even thousands of candidate Jurassic molluscs? (Can anyone comment?). Part of me would love to throw myself into a study of this, but logic tells me that with limited time to devote to my hobby, and around 750 UK species of moss, 800 larger moths, 3500 larger fungi, a similar number of lichens, 4000 species of beetle, 7000 flies, heaven only knows how many mites and nematodes...I have more than enough living species to occupy my time without embarking on a study of the extinct ones.

I am left with one lead as to species. In discussing locally discovered Corallian fossials, the book above shows images of fossil oysters of the species Nanogyra nana, corals of the species Isastrea explanata and Thecosmilia annularis and sea urchins of the species Nucleolites scutatus. Whether any of these were truely present in my garden I do not know, and even if they were they're not living there now and so strictly I shouldn't count them in my species tally. Since this is 'my party' however, I am going to flagrantly break the rules, assume at least one of them did once live in my garden, and chalk up one more species to my blog count. Complaints should be addressed to my lawyer!

Comma butterfly Polygonia c-album

2010-01-06T14:23:00.025Z

I am an amateur naturalist trying to learn something about everything living in my garden.

January is seeing heavy snow falls in the UK and as I write there is more than a foot of snow in my garden. To remind us of those balmy summer afternoons during these dark winter days therefore, a picture of a butterfly on the buddleia bush I've blogged previously.

The unusual shape of my butterfly - unique amongst British species - leaves no room for mistaking it as anything other than The Comma (Polygonia c-album).

The species name c-album was a new one for me (I'd not come across a hyphenated Latin name before). The Latin album or alba generally means you should look for some white feature on your animal or plant. All is revealed when you learn that the butterfly carries two distinctive white letter-c's (or white "commas" - if you prefer the English common name) on the lower face of its wings. Unfortunately I don't have a photo but you can find one here.

I read here that male Commas are territorial. They take up residence on a particular leaf or somesuch, ready to chase after anything that flutters-by in the hope it may be a passing female, returning afterwards to the same leaf. I've written previously about the inspirational studies of the great naturalist Niko Tinbergen into the subtle behaviour of butterflies in such circumstances.

In the early 19th century Commas were rare in Britain (see here) possibly for reasons connected with an increase in the practise of burning of hops (a foodstuff of the caterpillars) at the time (see here). Since then however, numbers have grown to the point where the Comma is today relatively common throughout Britain. The caterpillars are striking (see photo here), with markings that camouflage them as birds droppings.

I have frequently remarked (to the point at which I fear I may be becoming a bore on the subject!) that amongst my greatest pleasures in writing this blog has been the discovery that almost any life form I come across, no matter how seemingly commonplace, will turn out to have some unusual and fascinating facet to its lifestyle or behaviour. Take the ability of the Peacock butterfly to emit sounds to startle predators, or the high latitude melanism exhibited by Hebrew Character moths. The Comma is no exception, possessing as it does a somewhat unusual breeding cycle: Adult Comma's emerge from hibernation in March. Eggs are laid, and caterpillars appear from the end of April through to mid-June. It turns out that Comma caterpillars show a peculiar sensitivity to day length. Firstly, it will be obvious that caterpillars appearing early in the season will experience a day-length that is increasing from day-to-day whilst those hatching later experience a decreasing day-length. After a period of growth the caterpillars pupate. When the adult butterflies emerge, it's found that those emerging from the pupae of 'decreasing day-length' caterpillars have dark undersides. These enter hibernation shortly afterwards, to re-emerge in Spring and repeat the cycle. By contrast, adult butteflies from earlier (=increasing-day length) caterpillars are lighter-underwinged and, rather than entering hibernation, go on to breed a second generation of adults before winter arrives. By tracking day-length in this fasion, the species gives itself an improved chance of arriving at winter with a good sized population of adult Commas.

All of this was first worked out by one Emma Hutchinson (1820-1906), who sounds to have been a remarakable lady, being a Herefordshire vicar's wife and 'renowned breeder' of butterflies and moths. There's a nice article about her by D. Jackson in this online edition of the magazine (entitled, appropriately enough, The Comma) of the West Midlands branch of Butterfly Conservation.

Along with hops, British Comma caterpillars will eat nettles. Interestingly, Swedish Commas are far less fussy, being known to feed on plants from seven different plant families. To the professionals this raises intruiging questions about how such dietary variation might be encoded within a species DNA, how it is inherited down the generations, and the evolutionary impacts of such a variation within the one species. P. c-album has been much studied in this regard. A paper by Nylin et.al. (Biol. J. Linnean Soc. 2005, 84, 755) available online here is an example, and explains that dietary prefence in the Comma is encoded on the X-chromosome of the male butterflies.

Finally, my searches led me to an intriguing comment in a paper by Vanhoutte et.al. (J. of. Neuroscience Methods, 2003, 131, p195). The paper is rather technical and I haven't taken the time to follow the details, but roughly the authors set out to study the optical properties of the eyes of various butterflies. As everyone knows, insects have compound eyes made up of hundreds of identical ommatidia (the little hexagonal facets that tile together to form the eye)...

... "identical" that is, until you read in the introduction to the paper above that "recent research has shown that the ommatidia of butterfly eyes can be highly heterogeneous " (=variable)...

...except that P. c-album itself has rather homogeous (=non-variable) ommatidia!

All of which suggests there is more to butterfly eyes than meets the eye. Anticipating future butterfly postings, I've not gone much further into exploring this topic at present, but the few quick searches I've done suggest this is very much the case, with butterflies appearing to have a superiority and variety to their 'apparatus' for colour vision unique amongst insects (there's a review article by Frientiu et.al. here).

And amidst all this talk of fluttering butterflies in summer gardens, what of my garden right now? Answer: -5'C and falling!

A freshwater ciliate

2009-12-27T22:11:00.022Z

I am an amateur naturalist trying to discover everything living in my garden.

Some time ago I wrote about the Haematococcus algae I discovered in a puddle in my garden. At the time I enthused about the book Freshwater Microscopy by W.J. Garnett, a guide from another era for the amateur to culturing and identifying pond life. Inspired by the book I recently revisited my puddle and was well rewarded with a number of tiny critters new for me. Photo 1 (click to enlarge) shows three : a) A ciliate (more below) b) what I think may be a cyanobacterium and c) another ciliate that I think may be a paramecium. (As always my identifications come with a health warning. I'm happy to have them corrected).

Photo 2 shows a closeup of 'a' taken at 1000x magnification using my microscope's oil-immersion lens. Features to note about my organism are its large nucleus and the numerous swimming hairs (cilia) covering its body.

Those interested in such arcane matters (those not may like to skip this paragraph) may like to know the specimen here was stained with ~0.01% aqueous Eosin dye then mounted in a mix of water and glycerin with a little added disinfectant (to prevent future growth of mould). In an attempt to render the slide permanent I adopted the 'double cover slip method' . There's a detailed explanation of this here but briefly it involves sandwiching the specimen in its aqueous mountant between two differently sized coverslips, then mounting this sandwich in turn in a solvent based mountant (Permount in my case) thereby sealing in the aqueous mountant against evaporation and hopefully rendering the whole arrangement permanent. (Since acquiring my hobbyists microscope a couple of years ago I've developed a growing passion for making up microscope slides!)

Returning to my specimen itself, I have a couple of basic photoguides to pondlife and from images in these, and the general size (~40um) and form of my ciliate, I was tempted to identify it as a species in the genus Colpidium. You can find some stunning photo's of this and other protozoa here. From the volume of images on the web this seems to be a not uncommon find in pondwater. Unfortunately however, having looked at the equally splendid Protist Images website I'm no longer so confident. The problem is that the phylum Ciliphora (=little organisms like mine with cilia) is broken down into such a large number of superficially similar genera that it's hard for the amateur like me to know that my wee beastie is definitely a Colpidium and not say, a member of the catchily entitled Trithigmostoma, or the Drepanomonas, or the Cinetochilium...or for that matter the Tetrahymena I hear you cry! The Protist Database does give some guidelines for discriminating amongst these genera - typically discrimination involves carefully noting the position of mouth parts, the presence/absence of any stiffer bristles amongst the more whiskery cilia, or the absence of cilia on some parts of the body - but I confess I've not attempted to apply these to my organism since, firstly, the time commitment, my limited number of specimens and my comparatively humble microscope setup would, I'm sure, limit my chances of a successful identification. Secondly, there exists a nagging worry at the back of my mind that the taxonomy ('family tree') of the protozoa may not in fact be correctly established at this time. Certainly, the arrival of DNA sequencing technology is requiring that large amounts of what was assumed to be true about the inter-relationships of different species in other fields of biology is having to be drastically revised. The problem is that what two species look like is not necessarily a guide to how closely related they really are. DNA testing is revealing that superficially similar organisms can sometimes be only distantly related. The opposite is also true. I wrote about this in detail in my previous posting on the Glistening Inkcap Coprinus mushroom. I have no knowledge of the true status for microscopic cilates but I would not be at all surprised to learn that their taxonomy is also undergoing something of an upheaval amongst the professionals. For this reason also I've not attempted a more detailed identification of my ciliate. Of course, my thinking on all this may be entirely wrong. Perhaps someone looking at my photo's can tell immediately what species I have. If so, and you're that person, do please leave a comment.

Fieldfare Turdus pilaris

2009-12-25T09:26:00.023Z

I am an amateur naturalist trying to learn something about everything living in my garden.

Happy Christmas!

And what better way to enjoy the day than with a photo of one of my favourite visitors to the British garden: the Fieldfare (Turdus pilaris). Photos 1 and 2 show rear and front views (captured using my home-made camera trap incidentally).

I have an apple tree in my garden, which, besides providing a home for various lichens and mosses (not to mention a resting post for beeflies!) yields a bumper crop of cooking apples. So many in fact that that I have given up trying to collect them all and lots are left to lie on my lawn where they fall. They may look a bit untidy but this is more than made up for by the large numbers of Blackbirds, Fieldfares, Song Thrushes and other birds they attract come winter. In my garden, it is not unusual to find fifty birds at a time feeding upon them .

At 26cm in length and 100g, Fieldfares are a little larger and stockier than Song Thrushes (the BTO site has a host of biometric data). They eat invertebrates and berries (and apples!).
Fieldfares are not really resident in Britain. I say 'not really' since, as I learn from my copy of the RSPB Handbook (Holden and Cleeves) in fact a first British breeding pair was recorded here in the Orkney Isles in 1967. Over subsequent decades the number climbed to a peak of 13, but has since fallen back to less than five pairs a year. Of the population of one million individuals in Britain and Ireland, the overwhelming number are winter migrants, arriving here from late October from Scandinavia and Northern Russia.

Attempting to learn something further about Fieldfares I did a quick internet search and came across an interesting online paper by O. Hogstadt Nest Defence Strategies in the Fieldfare (Ardea 92(1), 79-84) in which the author reports studies of the response of nesting Fieldfares to effigies of crows and stoats - common egg predators of the Fieldfare. The Fieldfare's under study showed a distinct and rather well optimised reaction to these two predators. With crows, the reaction was to try to deter the attackers by defecating on them. This makes sense as fecal matter would certainly be detrimental to the performance of a crow's feathers. With stoats however, the reaction of the Fieldfares was to silently slip away from the nest and delay their return - eminently sensible when faced with a predator that hunts mainly by smell and is an equal danger to eggs and adults alike.

To end why not a few lines of poetry. These from the Cornthwaite by the British poet, Norman Nicholson (1914-1987):

Granite and black pines, where the migrant fieldfare breeds
And the ungregarious, one-flowered cloudberry
Is commoner than the crowding bramble.

A mushroom Psathyrella lutensis

2009-12-12T22:31:00.027Z

I am an amateur naturalist trying to identify everything living in my garden.

Photo 1 shows a small troop of mushrooms I found growing in some damp grass beneath my garden hedge.
From its general appearance my first thought was that these were a type of ink cap mushroom (see my previous posting here), but after watching them for a week there was no sign of any of the caps dissolving into an inky mess and it was clear further investigation would be needed.

The first thing to do when seeking to identify a mushroom is to take a spore print. This is extremely easy: place a cap, gills down, on any suitable surface, wait twenty minutes, remove, and hey presto - a spore print. That of my mushroom is shown in photo 2. Knowing spore colour (here, black) will typically allow you to rule out at least half the species in the average mushroom guide.

If you have a microscope it can also be valuable to ascertain spore shape and size. Mine were ovoid and around 12x6micron (photo 3).

Other features I noted for my mushroom were the the grooved (the technical term being striate) mostly brown cap, fading to white at the edge, and the 'flakey stem' (a.k.a. floccose stipe) in photo 1.

With these features in mind it was time to turn to the guide books. Unfortunately, such is the number of species of mushroom in Britain (more than 3000, with others, new to these shores, being recorded regularly) that no single guide book can cover them all. This proved the case for my mushroom. I failed to find it in the first three books I tried, the floccose stipe proving a rather troublesome feature, ruling out a number of otherwise similar small brown mushrooms in the books. It wasn't until I turned to my copy of Mushrooms and Toadstools (Cortecuisse and Duhem) that I found a picture of Psathyrella lutesnsis. All the features were there and I'm fairly confident in this indentification.

Cortecuisse describes P. lutensis as growing on damp ground (a fit with my location) and being scare-to-rare.

I have learnt in the course of writing this blog that almost any life form I come across will have some unique and curious aspect to its lifestyle (for example, its relationships with other creatures, its chemistry, or its means of reproduction). No doubt this is true of P.lutensis. Unfortunately my searches have failed to turn up any information about it whatsoever. Perhaps I have merely looked in the wrong places. On the other hand, so sporadic and fleeting may be its appearance that perhaps no one has ever studied my enigmatic little mushroom. If anyone knows more any more about it than merely its name, do please leave a comment.

Gooseberry sawfly Nematus ribesii

2009-11-21T07:29:00.027Z

I am an amateur naturalist trying to learn something about everything living in my garden.

I have a Gooseberry bush in my garden. In previous years I've had a good berry crop. But not this year! In May something attacked the bush, totally stripping the leaves. The culprit is shown in photo 1.

From closely similar photo's on the web I'm fairly confident this is the larva of the Gooseberry sawfly (Nematus ribesii). I should add my customary 'health warning' however: I'm not an expert on plant pests. As an amateur, you quickly learn that in natural history, identification of insects (fungi, spiders, lichen etc. etc.) solely on the basis of a photograph is always risky. There are more than a dozen species in the Nematus genus for example (see Bioimages site). I've found photos of only a handful. My caterpillar certainly looks like N.ribesii, but I don't know for certain it isn't one of the others. Can anyone more expert comment?

The damage done to my poor Gooseberry bush is shown in Photo 2. The branches would normally have been covered in leaves at this point in the year.

I did not spot any adult N. ribesii. From the photo's on Faroe Nature however it would appear they are squat, orange insects. This site has a drawing of the wing veinature taken from the book 'The Wings of Insects' (J.H. Comstock, 1918). (Wing veins are an important guide to insect identification - see my posting here).

In searching for articles on my sawfly I came across the admirable site of the Journal of Cell Science. This carries a large, searchable database of freely downloadable scientific papers. My searches turned up three on gooseberry sawflies (L. Doncaster, 1907, L. Doncaster 1905 and S. Shafiq, 1954). All get rather technical in places and I don't pretend to have followed all the details. From a quick read however, an interesting snippet I picked up is that eggs from both fertilised and unfertilised N. ribesii females can hatch but that larvae hatching from unfertilised eggs are overwhelmingly male. Eggs are laid in rows on the lower side of leaves at intervals of about a minute incidentally.

The main topic of the papers above relates to embryogensis i.e. the truly miraculous feat that Mother Nature manages of beginning with a single cell (an egg) and by a processes of repeated cell-replication and inter-cell communication constructs a complete insect (say) comprising hundreds-of-thousands of cells of countless types, all located in the right places, and all in an incredibly short period of time (about 4 days in the case of N. ribesii). Trying to undestand how she does this remains one of the great challenges for modern bioscience. It is perhaps fitting for this posting, that one of the most intensely studied creatures in all of science is a fruit fly (Drosophila melanogaster), flies being an ideal test-animal for such studies (along with nematode worms - see my post here) since dozens can be kept in a test tube where they will breed copiously and the offspring hatch rapidly. Armies of biologists have published innumerable articles about D. melanogaster - this site gives a flavour.

So there you have it, a seemingly humble garden pest with a rich natural history. Mind you, it might have been nice to have had a gooseberry crumble this year!

A macrochelidae mite

2009-10-13T20:46:00.044+01:00

I am an amateur naturalist trying to identify everything living in my garden.

On a whim, I recently got out my trusty Baermann funnel (which sounds far more technical than it actually is, namely, a sieve for sieving tiny critters out of soil) and was pleased to discover a host of new-for-my-blog creatures in a handful of old grass clippings. One, a mite, is shown in Photo 1 (click on photo's to enlarge)

Readers of my blog will know I make some effort to research the species of any creature I find in my garden. In the case of my mite however, this turned out to be no small challenge. Before this posting I knew nothing about mites. As I discovered, there are at least three factors mitigating against the amateur seeking to identify one to species level.

Firstly, there is the obvious minute size of mites' physical features. Identification to species can depend on close examination of some minute gland on the body or joint in the jaw-parts ('chelicerae'). With only one specimen and the type of microscope equipment typically available to the amateur, such features can be a challenge to view. The professional may perhaps turn to an extensive university collection of carefully dissected and permanently mounted specimens or examine their find by electron microscope. Sadly however, I don't have a electron microscope in my garden shed (I'm open to donations!).

A second challenge is the sheer number of mite species. More than 45,000 (here) have been recorded and some sources estimate this may be only 5% of the number awaiting discovery. To make matters worse there seems to be a dearth of elementary texts or online keys in the area. A number of advanced texts are available (at suitably advanced cost!) but there seems to be little along the lines of a field guide aimed at the amateur (I'd be pleased to be corrected on this matter).

Attempting to work through academic journal papers and keys brings one to a third difficulty, namely the dense jargon that accompanies the study of mites (acarology). The amateur must wrestle with references to such arcane structures as pretarsal condylophores, filiform corniculae and Claperede's organs. To complicate matters still further, acaralogists refer to the hairs (setae) that decorate mites' bodies in code ('h1', 'pg3' etc.) and not only does there seem to be no simple online explanation of how this code works (anyone?) but there is more than one system in use amongst the professionals.

Thankfully however, there are some notable exceptions to the comments above. On his excellent web site David Walter Evans has put together a Glossary of Acarine Terms, indispensable for making sense of the jargon of acarology. For discussion of some current research topics in acarology and some superb images see Macromite's blog. My searches turned up very few online keys but notable exceptions are the one on David Evans' site above and the interactive key here on the site of the North American Bee-Associated Mites project.

It was the latter that enabled me to make some progress with my mite. I spent some time inputting various features into the key with limited success, but then noticed my mite had 'brush like arthropodrial processes on the chelicerae' (in English: a fringe of hairs on its pincer-like mouthparts). You can see these in photo 2. In the key above this immediately narrows things down from my mite being in any of 36 possible families, to it being in the single family macrochelidae. (As always my identifications come with a health warning - I'm happy for them to be corrected)

Unfortunately that is as far as the key takes me and from the webpages of Dr G.W. Krantz I learn there are still well over a hundred individual species in the macrochelidae family. The book to consult would appear to be A Review of the Macrochelidae of the British Isles by Hyatt and Emberson, but this is out of print and seems generally unavailable.

In the course of my searches I pleased to discover that I am not the only UK amateur taking an interest in the fauna beneath our feet. Over at Alan Hadly's splendid site he too is busy studying macrochelidae mites (together with a host of other critters).

I must end this posting here. My intention in writing my blog is to learn something of the natural history of the creatures I encounter. It may not have escaped the attention of the observant reader however, that in this article I have largely failed to say anything about the natural history of mites. I feel relaxed! With 44,999+ species potentially still at large in my garden, I suspect this will not be the last time I have an opportunity to study these tiny creatures...

Dasineura urticae galls on a nettle leaf

2009-10-04T08:49:00.021+01:00

I am an amateur naturalist trying to learn something about everything living in my garden.

I've previously blogged the nettles (Dioica urticae) growing in my garden (indeed, I guess some of you reading this may even now be tucked up in your nettle bed sheets!) and also described some of the capsid bugs (Liocoris tripustulatis) I found living on them.

Recently I've noticed evidence of a second lifeform feeding off my nettles, namely the galls in photo 1.

I am fortunate enough to be in possession of a set of a dozen-or-so volumes of Field Studies, a journal that was at one time published by the Field Studies Council. This admirable UK charity runs a wide range of residential study courses aimed at the amateur naturalist. The Field Studies journal is no longer printed which is a pity as it commonly used to feature keys for the amateur wanting to identify some of the trickier plants and animal in our fields and gardens, including (for present purposes) a key to British Plant Galls by Redfern, Shirley and Bloxham in the October 2002 issue. Fortunately, for those of you without old copies of the journal to hand, this key has been reprinted. You can purchase a copy along with various other gall guides from the British Plant Gall society here.

Redfern, Shirely and Bloxham list five arthropods and one fungal rust capable of causing galls on British nettles. The pouch-like swellings with slit-like grooves in their surfaces on the leaf in photo 1 indicate these are galls caused by the small fly, Dasineura urticae. Had I cut open some of the galls (I didn't) I might have been lucky enough to find some of the white grubs of this fly. Indeed, as I learnt from the very nice 'A Nature Observer's Scrapbook' site, I might even have found some predatory grubs from another species, laid there to eat the Dasineura urticae grubs.

I'm very far from being an expert in diptera (flies). From the Bioimages site however it seems there are several dozen British species in the fly genus Dasineura. This site has pictures of the grubs and galls of some of them.

I have only found one description of an adult D.urticae fly: My copy of Insects on Nettles (Davis, Richmond Publishing) describes a "very small fly with long antenna. Under a microscope an antenna looks like a string of beads...". Unfortunately I haven't been able to find a photograph on the web, although the Bioimages site does carry a photo of another Dasineura species (D. sisymbrii) which I guess may be rather similar since it too has bead-like antenna.

Sadly, that is as much as I have managed to learn about my mysterious fly. How and when the adults mate, how a female locates a host patch of nettles, whether she lays eggs or live grubs, how long the grubs remain inside their gall... I can only guess at the answers to these and a host of other questions. Another garden study-project to add to my burgeoning list!

A Blood-Vein Moth (Timandra comae)

2009-10-03T10:42:00.019+01:00

I am an amateur naturalist trying to discover everything living in my garden.

What with photography, microscopy and literature searching, my self-imposed mission to catalogue my garden's life places lots of demands on my free-time. When I've a chance however I'm still making an effort to set out my home-made moth trap at night. I did so recently (on the 22nd August for the record) and it yielded a good haul of new species to add to my garden list, amongst them the attractive moth in photo 1.

My moth's common name is The Blood-Vein, for reasons that I imagine are obvious. It is a member of the large (several hundred species in the UK) geometridae family of moths, so called because of the caterpillars of these moths walk with a measuring (=hence 'geometer'), 'inch-worm'-like, gait.

From my copy of Moths of Great Britain and Ireland (Townsend and Lewington) I understand Blood Vein caterpillars feed on dock, sorrel, knotgrass and common orache. I've not been able to find a picture of one on the web (anyone?). Price, Goldstein and Smith studied the suitability of the Blood Vein for introduction into the States as a biological control agent against 'Mile a Minute' Weed (their paper is available here). (They found it was unsuitable)

Adult Blood Vein's are fairly common in Mid- and Southern Britain, but get rarer in the North.

The Blood Vein gets but a single mention in my copy of the excellent Moths (Michael Majerus). One might expect that such small and fragile creatures as moths might tend not to fly about in severe weather such as during heavy downpours. Surprisingly this seems not to be the case however: Majerus reports setting up a moth trap during a severe thunderstorm and trapping several hundred moths, undaunted by the driving rain, within hours. A dozen or so Blood Veins were among them.

The Blood Vein's scientific name is Timandra comae. There seems to be some confusion over the the relationship between this moth and the closely similar Timandra griseata. At various times the two have been lumped together as a single species, and at other times split out as two. Current work suggests they are indeed two separate species.

In Greek mythology Timandra was one of the daughters of the Spartan King Tyndareus and his wife Leda (she of swan-fame). Timandra's sister was Helen of Troy. King Tyndareus managed to upset the goddess Aphrodite and was punished with a curse that all his daughters would be adulteresses. Daughter Timandra duly obliged, eventually marrying one King Echemus only to later desert him for King Phyleus.

Now, whether in fact my moth has a particularly adulteress streak to its nature I really can't say. Indeed, aside from the snippets of information above, I've been failed to find any significant written accounts of the biology and behaviour of The Blood Vein. Whether this is because I've not looked in the right places, or whether it is that The Blood Vein, in common with so many other insect species, has simply not been studied in detail, I do not know. I'd be delighted to find out a little more about this pretty moth however, so do leave a comment if you can help.

A microscopic Peritrichia Cillate (Vorticella?)

2009-09-28T22:12:00.034+01:00

I am an amateur naturalist trying to discover what lives in my garden.

Readers of my blog may recall that some time ago I decided to investigate the microscopic inhabitants of some rainwater that had collected in my garden. I was delighted at the time to discover some mobile little Haematoccus algae. Spurred on by this success I recently decided to revisit a similar puddle.

This time the water was in shade and contained quantities of decaying leaf-matter. Placing a few drops under my micro- scope I saw nothing at first, but then began to notice numerous small, semi-transparent, stalked objects, such as those above the number '3' in the microscope photo 1 (click to enlarge). My first guess was that these were some sort of fungal spores. Then one moved!

Zooming in (Photo 2) revealed an ovoid creature with a fringe of hairlike cilia at the front end. You can just about make out one poking out above '2.7' on the scale bar. These cilia were in constant motion and set up eddy currents in the water, drawing in small food particles as I watched.

The move- ments made by my creature were highly charac- teristic. Any small distur- bance (such as a tapping the micro- scope slide) caused the stalk supporting the 'head' to rapidly contract, jerking the head backwards in the blink of an eye and at the same time changing the head-shape from ovoid to compact and spherical. Gradually over a period of perhaps half-a-minute the stalk would re-extend and the head return to its original shape.

My creature had one further surprise in store: I was amusing myself tapping the slide and watching the response, when, as if grown tried of my irritating presence, one of my little creatures suddenly detached itself from it's stalk and swam away!

I'm in possession of a nice introductory, colour Guide to Microlife (Rainis and Russell, Grolier Publishing) and I was relatively quickly able to identify my lifeform as a ciliate, the cilophora being a large collection ('phylum') of microscopic animals belonging to the even larger collection of microscopic animals, the protists (to get an idea of just how large you might like to peruse the 81,000 (!) images on the Protist database.)

Fortunately, the structure and habits of my creature allowed for some further progress: the presence of a contractile stalk, the cilia around the mouth and the fact that my little critter was able to swim free of its stalk all point to it being a member of the smaller (though still sizeable) subclass of organisms the peritrichia (which I read is from the Greek, peri=near, trichia=hair).

Now, had I observed any 'stalks' with more than one 'head', that might have narrowed things down to my creature being in the genus Epistylis. I didn't (though of course absence of evidence isn't evidence of absence), which finally brings me to the (somewhat tentative) conclusion that my little creature is a member of the genus Vorticella. Unfortunatly that's as far as I've got. There are a more than a dozen species in this genus and which mine is I can't tell. I'll be happy if anyone out there can tell me.

Naturally, I'm not the first microscopist to observe Vorticella and a little web browsing led me to two very nice articles (here and here) for the amateur. The latter includes some excellent photos including some of Vorticella reproducing by asexual budding. From these and other sites I also learn that a free swimming Vorticella 'head' is termed a telotroch and the stalk is able to contract by virtue of a contractile bundle of threads within termed a moneme. A paper by Sotelo and Trujillo-Cenoz (available to download here) has some ultra-high magnification electron-microscope photos of this and also reveals that the moneme is responsible for the shape-change the head suffers when the stalk contracts.

On the subject of cilia a quick web search turned up numerous papers and articles. My intention was talk about some here, but since I've already gone on for some length in this posting, and since I'm certain to have another opportunity to discuss cilia in the future (so many microscopic creature have them), I'll leave the topic for now.

Instead I'll end with a photo of a free-swimming little animal I encoun- tered in the same sample of water. The ident- ification of this one defeated me. Am I looking at a free swimming Vorticella or is this something else? If you know do please leave a comment.

Couch Grass (Elymus elegans) and Perennial Ryegrass (Lobium perenne)

2009-09-26T19:19:00.058+01:00

I am an amateur naturalist trying to learn something about everything living in my garden.

Success in discovering the identity of some plant or animal is all about the careful and methodical observation of details. I've written this before, and had I only paid attention to my own dictum, I might avoided wasting half a morning recently getting thoroughly confused over the species of some grass growing in a corner of my garden!

Intrigued by a comment in a booklet Practical Microscopy (Eric Marson, Northern Biological Supplies) - a superb guide I cannot recommend too highly to any amateur interested in preparing their own high quality microscope slides - I had set out to examine some blades of grass under my microscope.

Venturing into my garden I came across the grass in photo 1. The long, seed bearing structure is technically termed a 'spike'. I picked a little and came back inside but before putting it under the microscope I decided to try identifying the species using my copy of Grasses (Fitter et.al. publ. Collins). Having only a few inches of specimen, it wasn't long before I was stuck however. I went back outside therefore, found my clump of grass and picked a little more. Embassingly foolish as it seems now, this went on for nearly an hour, with me traipsing back and forth, collecting a little more grass each time and returning inside only to find myself more confused than ever.

Finally, in exas- peration, I threw away my growing collection of tattered grass cuttings and started a fresh, and this time, methodical study. The result was the arrangement in photo 2 and the belated realisation I'd been collecting bits of two different grasses!

The two in question are Couch grass (Elymus repens) (photo 2, upper) and Perennial Ryegress (Lolium perenne). Laid out neatly in photo 2 the differences are obvious. I can say that it underlines the lesson that one cannot trust that causal glance at that seemingly undifferentiated clump of 'spike bearing' grass swaying in the breeze!

One difference between the two grasses in photo 2 is leaf size. In fact however, this is not an overly useful guide to species identification, as the size of the leaf baldes can vary with their position on the 'stalk' (culm) and other factors (soil quality etc.). Instead, amongst the most useful guides to a grass's species is the shape and size of the ligule, a small vestigial leaf-like structure the nestles between the culm and a leaf. Photo 3 shows the ligule of Perennial Ryegrass. By contrast, Couch grass lacks a ligule (though just to confuse the unwary, the leaves wrap around the culm via two little sheath-like flaps know as auricles - see photo 4).

Returning to the spikes of my two grasses, photo 5 shows a closeup of both. These bear the grasses' minute flowers (the source of all that hayfever-inducing pollen in summer). As I learnt in my previous study of the Cultivated Oat (Avena sativa), the structure of grass flowers comes with a lot of botanical jargon. I'll not repeat it here, but for completeness I've labelled up photo's 6 and 7.

And what of that micro scope image I originally set out to acquire? Well, as everyone knows you can get a painful cut from the edge of a blade of grass. Putting one under the micro scope (photo 8) shows just why: a margin decorated with a row of tiny saw-toothed daggers. Another of nature's tiny miracles.

Common Wasp Vespula vulgaris

2009-09-19T09:07:00.027+01:00

I am an amateur naturalist trying to learn something about everything that lives in my garden.

Not everyone's favourite insect it must be admitted, photo 1 shows two wasps feeding on a rotten apple on my lawn (a habit shared with the mucor moulds I blogged previously).

The species here is the Common Wasp (Yellowjacket to those of you reading in the States) Vespula vulgaris, one of eight British species in the Vespidae family of social wasps. The hornet I blogged previously is another.

A number of the British social wasps are superficially rather similar and it can pay to take a close look at the face (photo 2) to be confident of the species. Were my wasp to be the not-uncommon German Wasp (Vespula germanica), for example, then it would have three little black dots in the centre of its face (mine doesn't). You can find a nice set of photos of the various British Vespidae species here.

Photo 2 also reveals my wasp is female: Her antennae have 12 segments (males have 13).

Wasps have been very common in my garden in recent summers and this is no doubt partly explained by the impressive abandoned nest (photo 3) I found in attic last winter.

Wasps have two pairs of wings, with each pair comprising a larger- and smaller wing. A pair gets 'zipped' together when the wasp lands so that it appears to be only a single wing. You can see this in photo 1. Taking one of the smaller wings and putting it under the microscope reveals that the analogy to a zip is well chosen: a row of hooks lines the edge of the smaller wing, allowing it to hook tightly onto the larger. Personally I never tire of looking at structures like this under the microscope. Any engineer will tell you how enormously demanding it is to machine mechanical devices to micron accuracy, yet mother nature is routinely able to grow fantastically intricate structures out of such unpromising materials as chitin or cellulose.

My efforts to learn something about Common Wasps led me back to the subject of 'worker policing', which you may recall I touched on in my posting on hornets. Briefly, it turns out that female workers in the colonies of many types of social wasp, bee and ant permit only eggs from the queen to hatch. Eggs laid by female workers are removed from the colony by other workers before they hatch. To the evolutionary biologist, this begs the simple question 'why?'. What advantage does the colony gain by only tolerating the eggs of a single individual (the queen)? Many learned papers have been written on this subject and I wouldn't presume a detailed understanding of all the technicalities but in brief, I understand the reason relates to so called 'kin selection'. It turns out that as a female worker, you are more likely to be closely genetically related to a grub hatching from a queen's egg than you are to one from the egg of fellow worker. Maximising all individuals' relatedness to each other is therefore achieved by preferentially rearing the queen's eggs.

Now, all of the above is as I explained it in my hornet posting. Whilst I didn't doubt the explanation, what I'd struggled to do there was to understand for myself in simple terms precisely why workers relate more closely to the queen's egg than to those of their sisters. In preparing this posting however, I came across the commendably readable More Than Kin and Less Than Kind by Douglas W. Mock. The key information I'd been missing concerns the way in which genes are passed down the generations in these many insects. Firstly it turns out what whilst female wasps each carry two sets of chromosomes (making them 'diploid' - just like us), males carry only a single set (they're haploid). Secondly it transpires that queens in insect colonies that practise worker policing, typically mate with multiple males. The sperm from all the queen's male partners is mixed together and stored in a vessel inside her body known as the spermatheca until needed to fertilise an egg. Which male's sperm fertilises which egg is then random. Taking these two facts together (the haploid/dipoloid male/female divide and the queen's 'random polygamy'), and working through some relatively simple genetics (anyone who remembers Mendel's sweet peas from school biology lessons should follow it), its not too hard to follow the chain of logic that shows that as a female worker born to a queen, you'll have a closer genetic resemblance to eggs from your mother than you will to eggs from your sisters.

And finally, I learn from a paper by Landolt et.al. that a good way to attract Vespula vulgaris wasps is to fill a vessel with acetic acid and isobutanol... of course, alternatively you might simply try eating a sandwich in your garden in August!

Gatekeeper Pyronia tithonus

2009-08-20T19:29:00.028+01:00

I am an amateur naturalist trying to learn something about everything alive in my garden.

Photo 1, taken on a sunny day in recent July shows a butterfly I found resting on a post in my garden. A few minutes with a butterfly guide and there's no mistaking it as The Gatekeeper (Pyronia tithonus).

My Gatekeeper was very obliging and gave me oodles of time to fetch my camera and take photo's. I might have thought nothing of this, but then I came across a nice online study by Christopher Young of 516 butterflies visiting a UK garden over three seasons. P.tithonus 'stuck around' for the longest of all. Whether this is simple coincidence or whether it points to a behavioural trait of the Gatekeeper I've no idea (an unrecognised butterfly habit awaiting study?).

A second common name for the Gatekeeper is the Hedge Brown. For some reason I prefer the first, though I can't imagine how it originated (anyone?).

The Gatekeeper in photo 1 is a male as confirmed by the dusky patches towards the centre of the forewings. In preparing this posting I came across a number of websites declaring that these are a source of pheromones. I haven't managed to locate an authoritative account to confirm this however (anyone?).

The Gatekeeper is a member of the Nymphalidae family of butterflies that includes some 25 UK resident species, amongst them my previously blogged Peacock . An obvious feature of both are the 'eye' spots. My quotation marks are carefully chosen having come across an interesting article by Stevens et.al. As I learnt in researching my Peacock butterfly posting, many studies have shown that the conspicuous wing spots of certain butterflies have a valuable effect as anti-predator devices, acting to startle small birds about the seize the insect. It has been widely assumed that the reason for this is that, to the birds, the wingspots resemble the eyes of larger predators (hawks, owls etc.). The paper by Stevens et.al. casts doubt on this however since their ingenious test experiments imply that the most effective patterns are not necessarily those that most closely resemble the eyes of predators.

Caterpillars of the Gatekeeper eat grasses. You can find an image of one here.

Sadly, that is as much as I have managed to learn about the Gatekeeper. I should like to have read a 2001 paper by Conradt et.al. that my web searching tuned up. From the abstract, I understand the authors' studies to have shown that P.tithonus can detect and orient itself by landmarks up to 150m away (an impressive distance sensing range for a small insect I'm sure you'll agree). Sadly however, like so much internet information about the natural world, the details are viewable only by making a payment to a private publishing house. Not something I, as am amateur, am inclined to do. Alas therefore, my curiosity and yours, dear reader, must go unsatisfied!

Common Toad Bufo bufo

2009-08-17T20:05:00.017+01:00

I am an amateur naturalist trying to learn something about everything alive in my garden.

Weeding out my shrubbery recently, I was pleased and surprised to come across a second example of a UK amphibian to add to the first (a common frog) I wrote about last year: specifically a rather large toad. Sadly, by the time I had raced to my house and returned with my camera my toad had disappeared. My luck was in however as a few minutes spent hunting through the undergrowth turned up a second: the little fellow in photo 1.

Britain has only two species of toad. One, the Natterjack (Epidalea calamita), is a rare and protected species. I have never knowingly seen one myself. Our second is the Common Toad. There are various ways to tell the two apart but the most useful from the point of view of photo 1 is the paratoid gland which I've marked with a 'p' in photo 1 (click to enlarge). The fact that this is rather regular and pronounced indicates that mine is a Common Toad (Bufo bufo).

What I've learnt about the Common Toad has been mostly through reading The British Amphibians and Reptiles (Malcolm Smith, Collins New Naturalist). With regard to diet, the book contains the amusing quote (attributed to Newman 1869) "[the food of the toad] seems to consist of all living things that are susceptible to being swallowed". Bees, ants, whole snails, moths and young snakes have all been recorded in the diet of the Common. In the case of some larger South American and African toad species even full grown live mice are taken.

It seems possible the first, larger toad I saw and the second smaller one were a female and male respectively. Male Common toads average 60-65mm. Females are typically 10-15mm longer.

Common toads can live a surprisingly long time. Forty years has been recorded in captivity. They hibernate on land in burrows from around mid-October until mid-March when they emerge to spawn. Spawning continues until around the end of April. As is well known, toad spawn forms long 'necklaces' in the water as opposed to the more amorphous blobs formed by frogspawn.

Finally, a word about the predators of the Common Toad. Crows, magpies, rats and snakes are all known to eat toads (some of the former tending to eat the innards, leaving behind the unpleasant tasting skin). Prize for most gruesome predator has to go to the greenbottle fly Lucilia bufonivora however. Having located a victim an adult bufonivora lays up to 100 eggs on its unfortunate victim's back or thighs. Some time later the eggs hatch and the emergent maggots immediately make their way up the toad's back and into its eyes and from there into the nasal cavity. Within a few days the toad is dead. The maggots devour the corpse before dropping off to pupate in the soil and emerge a week or so later as adults ready to repeat the cycle. For those with a strong stomach you can see a photo of an infected toad here.

The Collared Parachute mushroom Marasmius rotula

2009-07-29T13:20:00.017+01:00

I am an amateur naturalist trying to catalogue all the life in my garden.

No, despite appearances to the contrary, I have not gone away! My camera has been kept busy over summer snapping pictures of a host of interesting creatures in my garden and it's high time I resumed the task of writing about them.

Some weeks ago I was clearing away a patch of weeds bordering my vegetable patch and I came across a troop of the lovely little mushrooms seen in photo 1 (click to enlarge). They seemed to be growing on a lump of decaying wood.

A quick look in my mushroom guide and I'm fairly confident my mushroom is a Collared Parachute Marasmius rotula.

I say 'fairly confident' as Marasmius bulliardii is similar in appearance though I read it is typically somewhat smaller than rotula and grows on leaves . You can find pictures of both, plus various other species, on the splendid Bioimages site and a key to some 60+ Marasmius species on Michael Kuo's site.

Had I gone to the trouble of taking a spore print (see my previous posting here), and assuming my mushroom is indeed M.rotula, I'd have found the spore colour was white. Under the microscope the spores are 7-10um x 3-4um in size and elliptical.

Turning to my copy of the excellent Fungi (Spooner and Roberts, publ. Collins) a nice thing to learn about Marasmius mushrooms is that one of them is amongst the world's oldest toadstools. A Marasimus-like mushroom ('Archeomarasiumus liggetti') was found, trapped in a 90 million year old piece of amber, in New Jersey by one David Hibbett, a Harvard mycologist. The American Museum of Natural History webpage carries a photo and Hibbett's webpage includes a link to his 1997 paper on the discovery ('Fossil mushrooms from the Cretaceous and Miocene ambers and the evolution of homobasidiomycetes' ).

And finally, the exceptionally sharp eyed of you may have spotted a second life form in photo 1, namely the little reddish insect clinging to the cap in the centre. Photo 2 shows a close up of the little critter. Some remarkably complex relationships exists between fungi and insects. The grubs of certain woodwasps for example, though partial to chomping holes in trees, are only able to ingest wood that has been first rotted by a fungus. Adult woodwasps therefore carefully transport this fungus in special grooves on their body and introduce it the same hole as their offspring. My little insect in photo 2 has a superficially wasp-like look about him or her, but his or her true identity and whether he or she has any sort of relationship with my mushroom, or simply happened to be passing through when I took the photo, I have no idea. If anyone of the experts out there can offer any information do please leave a comment.

Hebrew Character ( Orthosia gothica) and Common Quaker (Orthosia munda)

2009-04-04T07:15:00.019+01:00

I am an amateur naturalist trying to identify everything that lives in my garden.

Photo 1 shows two more moths I caught (for the record, on 26th March) in my recently- constructed moth trap.

I didn't know the species of either at first but from my copy of Moths (Waring, Townsend and Lewington, British Wildlife Publishing) it's clear I've found (left) a Common Quaker (Orthosia cerasi) and (right) a Hebrew Character (Orthosia gothica).

I should easily identify them in future: the two, kidney-shaped wing spots of the Common Quaker and the black shapes on the wings of the Hebrew Character are very characteristic.

The Hebrew Character gets its name from the resemblance of its black wing markings to the letters (characters) of the Hebrew alphabet.

I was puzzled by the origin of the name 'Common Quaker' but then came across an article from the Times newspaper 2003, describing an interview with the naturalist Peter Marran. It seems that many of the common names for British moths were made up by members of the The Aurelian Society - one of world's first entomological societies, established in London in the 1760's. According to the article, Quaker's of the time wore (quotes) "subfusc attire" (i.e. dusky or drab clothes). This inspired the naming of not one but three British moths: The Powdered -, The Twin Spot- and (our moth here) The Common Quaker.

Adult of both the Hebrew Character and the Common Quaker feed on the nectar from sallow catkins whilst their caterpillars will eat a range of plants including Oak, Birch and Hawthorn.

An interesting feature of the Hebrew Character I learnt from reading Michael Majerus' book Moths (The New Naturalist Library) is that it displays high latitude melanism; In Northern Scotland, a form of the Hebrew Character - specifically Orthosia gothica f. gothicina - is found that lacks the black colour to the 'Hebrew letters' on its wings. Some other moths, notably the Scalloped Hazel and the Ingrailed Clay, also shows a distinct form at high latitudes. Why? Because, high latitudes impose some unique selective pressures on the moths that live there: firstly there may be issues of thermal regulation (having dark or pale wings will effect how easily a moth heats up or cools down); secondly the low angle of the sun creates softer lighting conditions that may mean birds can more easily pick out camouflage patterns that might work well elsewhere; thirdly, at high latitude in summer the sun does not set - a challenge for the camouflage of normally night flying moths. Low latitude moths that want to 'make the transition' to high latitudes are therefore faced with the need to adapt their colourings or suffer the consequences. A wonderful example of evolutionary change.

Bee Fly Bombylius major

2009-04-01T14:15:00.019+01:00

I am an amateur naturalist trying to identify everything that lives in my garden.
Photos 1 and 2 (click to enlarge) show what must be the most dramatic 'nose' of any British fly.

A quick look through my copy of Michael Chinery's book Insects (Collins) and it appears that I've come upon a Bee Fly (Bombylius major). There are ten British species. B. major is the most commonly observed.

Bee Flies use their 'nose' (proboscis) to probe flowers for nectar. The length arises from their preference for hovering above, rather than actually landing on, flower heads. They do this presumably to avoid being ambushed by predators such as Crab Spiders that sometimes lurk behind flower petals.

Apparantly Bee Fly's are superb ariel acrobats. I didn't get a chance to observe this however since the one in the photo remained stubbornly perched on the branch of my garden apple tree. We'd had a few warm Spring days here in Oxforshire. On the day the photo was taken however it had turned cold and my Bee Fly was very sluggish (he/she was still on the same spot half an hour later).

I've not found a specialist UK site devoted to Bee Flies, but you can find a key to those of Canada here.

The best general description of Bee Fly natural history I've come across on the internet is that of Louise Kulzer. They have a complex life cycle. As above, adults feed on nectar. Their grubs are parasitic on solitary bees and wasps however. An adult Bee Fly lays it eggs near the burrow of a (true) bee and the grubs, once hatched, find their way into the nest and consume the food intended for the (true) bee larvae. Later, the Bee Fly grub undergoes a 'shape change' (hypermetamorphosis) into a carnivorous grub, and eats the (true) bee larvae.

That at least is a general description. Ideally I'd have liked to have found some more specific details about my species Bombylius major (What types of bee/wasp species it parasitises; How the Bee Flies tracks down a host-bee's nest etc.) but sadly there seem few descriptions on the web. I did find one other site that references a paper by one T.A. Chapman, specifically on the life history of B. major ...from 1878! (I haven't been able to find a copy)

My searches were not entirely in vain. I did come across the studies of Catherine Toft who has written about the ecology of Bee Flies in the Californian Desert, in particular observations on the foraging behaviour of two species. My amateur understandingof her work is as follows:

Back in the late 1960's, one T.W. Shoener argued that, other things being equal, females in nature should seek to maximise the time they spend feeding (on the assumption that taking in more energy through feeding translates into being able to produce more offspring). Males on the other hand should be 'time maximisers' i.e. beyond basic dietary needs, time spent feeding is in some sense 'wasted time' away from looking for, and breeding with, females. Dr Toft noted that two species of Bee Fly (Lorodotus pulchrissimus and L. miscellus) lent themselves very well to a study of this since the two species of fly live in an essentially identical environment, sharing the same desert habitat and even feeding on the same plant.

As it turned out, L.misecellus matched the Shoener prediction: females spent more of their days foraging than males. Males of L. pulchrissimus bucked the trend however. They spent exactly the same amount of time foraging as females. This is apparantly a feature they share with male moose! Although Dr.Toft offers some tentative explanations as to why this might be. The ultimate answer appears to await a deeper study however.

All of which suggests to me, that should you be an amateur naturalist reading this and searching for an amusing but scientifically useful 'project' to undertake in your neighbourhood this summer, you could do worse than to sit in a deckchair with a cold drink and a stop-watch, and time the foraging patterns of that little-known bug in your backgarden!

Candlesnuff fungus Xylaria hypoxylon

2009-03-28T08:59:00.020Z

I am an amateur naturalist trying to discover everything that lives in my garden.
Chomping its way through a fallen twig, photo 1 shows a collection of the 'candle wick-like' fruiting bodies of the Candlesnuff fugus Xylaria hypoxylon.

This fungus is very common here in the UK. Scan piles of logs or fallen branches and you're likely to spot it on almost any country walk.

In common with the holly leaf fungus I blogged recently, and the morel before that, X.hypoxylon is a member of the ascomycetae - a huge collection (phylum) of fungi that 'grow' their spores inside microscopic tubes called asci.

In the case of X. hypoxylon a couple of hunded asci are, in turn, packaged into a structure called a perithecium - basically a small 'pimple' with a hole in the top through which spores, once liberated from an ascus, escape. There's an excellent cross sectional microscope photograph of a perithecium of one on the mycolog site (it's a big webpage - the photo's about half way down).

To the eye, the perithecia of X.hypoxylon appear as tiny black pimples on the surface of the white 'candle wicks'. You can see some in photo 2. (Perithecia are common features of lichens also (see my post here).) Over time, the surface tends to become increasingly covered with these pimples (compare Photo 1 with Photo 3 taken about two weeks later) until finally the 'wick' ('compound ascoma') appears quite black. The resulting 'charred' look gives the name pyrenomycetes (from the Greek 'pyr' = fire) to the class of mushrooms of which X.hypoxylon is a member.

The definitive web site on the pyrenomycota is that of by J.D. Rodgers.

In fact the life cycle of X.hypoxylon is a little complex. The spores liberated by the pimply black perithecia are the result of sexual reproduction. X. hypoxylon is also able to reproduce asexually via so-called 'condiospores' however. These conidiospores give the fungus its white powdery appearance in photo 1.

Seen under the microscope, the sexual spores of different species of mushroom show characterisitic differences in size and shape (a helpful aid when trying to identify a mushroom - see my previous posting). I read on Michael Kuo's site however, that conidiospores from different fungi all look basically the same. Why nature has chosen to distinguish sexual and asexual spores in this fashion I can't imagine. Can anyone comment?

A black lichen Placynthium nigrum

2009-03-24T21:17:00.000Z

I am an amateur naturalist trying to discover everything living in my garden.

Spring is well and truly springing here in Oxfordshire. Soon animals and plants will be appearing in my garden faster than I can photograph them, let alone write about them. Whilst things are still moderately calm therefore, I'm seizing the moment to press on with my task of cataloguing my garden's lichens.

Quietly going about its business, photo 1 (click on photos to enlage) shows a black crustose lichen (for the uninitiated, see my explanation here) that decorates my garden wall in places. Photo 2 is a closeup (I've slightly digitally sharpened this image using software).

I'm no expert, and happy to be corrected, but from what I can tell from leafing through my copy of Lichens (Frank Doson), although there are numerous lichens with black fruiting bodies ('apothecia') on otherwise coloured 'backgrounds' ('thalli'), there are only a handful of mostly- or wholly-black crustose lichens to be found in Britain. A number are marine. Verrucaria maura, for example, is common on rocky shorelines where it is somtimes mistaken for oil pollution.

Of the mostly black, 'land-locked', lichens, I spent some time looking at the photos of Verrucaria nigrescens on the excellent 'UK Lichens' site. Looking closely however, this seems to have a more chocolate-brown thallus, albeit one peppered with many black 'perithecia' (see my definition here).

On balance therefore I'm tentatively identifying my lichen as Placynthium nigrum which my copy of Dobson describes as being "Very common, mainly on hard calcareous substrates throughout Britain. Often found on flat tombstones and cement".

A slight puzzle is that the photo in Dobson shows a more powdery ('coralloid') surface than is evident in my photo 2, although the book adds this lichen may be "sometimes smooth and cracked especially in polluted areas". Where I live is rural and I don't believe especially polluted. That said, some lichens are extraordinarily sensitive to even minute amounts of air pollution - whole books have been written on this topic. Anyhow this variability in texture gives me some added confidence in my identification.

Turning to my copy of Lichens (Oliver Gilbert, New Naturalist Library) a nice thing to discover was some growth-rate data for Placynthium nigrum. I learn that young patches expand their radius at 1.66mm/year and mature patches at 0.08mm/year. Lichenometry is the technique of dating old structures (churches, stone circles etc.) by studying their lichen populations - you can find an article here. Applying the data above to the approximately circular, 10mm-radius, patch in photo 2 ages my lichen at between 6- and 125-years old! Not the most exact figure I grant you, but fun to know.

As I commented in a recent posting, I am puzzled by the colours lichens adopt. Over the millenia animals have been driven to evolve their numerously-coloured fur coats, feathers and exoskeletons so as to optimally attract mates, hide from predators, advertise their venomous stings etc. Similarly my amateur's understanding is that plants are mostly green by virtue of the need to pack their leaves and stems with chlorophyll. Even various of the larger mushrooms have evolved specific colours, presumably to alert browsers to their poisonous nature or advertise their presence to 'pollinating' (botanists may wish to turn away at this point!) insects. Some even glow in the dark for this very purpose. But how it is that some lichens on my garden stonework gain advanatage by being coloured matt black, whilst others 'prefer' greyish/white and still others, bright yellow, I struggle to guess. Can anyone help?

Today's posting brings my garden lichen species-count to eight. I feels that I may be approaching completion with regard to this particular lifeform. Until, that is, I find another dozen species through more careful inspection of my garden's rocks and trees. Stood outside earlier today for example, when acquiring the photos above I was aware only of our black friend and of the grey-white patches which (though I haven't checked in detail) I'm assuming is our old friend Verrucaria. Sitting now at my computer screen however, staring at an enlarged version of the photo 1, I'm suddenly noticing the array of tiny orange blobs towards the centre of the image. Time to go back outside methinks!

A Snowdrop Galanthus

2009-03-24T18:21:00.003Z

I am an amateur naturalist trying to learn a little about everything living in my garden.

Hot on the heels of one of my favourite garden birds, one of my favourite flowers: The Snowdrop (the photo was taken back in mid-February)

Snowdrops are members of the plant genus Galanthus (from the Greek 'gala'=milk, 'anthus' = flower). What I've learnt about them has been mostly through Mark Smyth's very nice Snowdropinfo website, the Royal Horticultural site, the BBC site, and from my trusty copy of The Englishman's Flora (Geoffrey Grigson).

Firstly, regarding the name, both the RHS site and Grigson state that 'Snowdrop' derives from the German word Schneetropfen, a type of ear ring popular in the 16th and 17th century. Now, whilst I'm entirely happy to accept this, neither author gives a reference without which it's not immediately obvious to me that likening this plant to a 16th century German earring is more likely than people having chosen the 'Snowdrop' after... er, well...drops of snow! (Anyone?)

Geoffrey Grigson lists other folk names including Eve's Tears and Candelmas Bells, the latter a reference to the Christian festival of February 2nd when Snowdrops are one of the few plants in flower.

The snowdrop, in purest white arraie,

First rears her hedde on Candlemas daie

(Early church calendar of English flowers, c. 1500 - see here)

According to the BBC's site, bringing Snowdrops into the house at Candelmas symbolises a death.

Snowdrops are widely spread across Europe and Asia. There are nineteen true species (there's a list on Wikipedia's Snowdrop page) and literally hundreds of artificial cultivars, with new ones created all the time by enthusiasts ("Galanthophiles"), and old varieties occasionally re-discovered in sleepy vicarage gardens or (see the National Trust site here) on overgrown Victorian rubbish dumps!

You can find a photo-gallery of cultivars on Mark Smyth's site. What characteristics elevate nineteen types of Snowdrop to true species level I'm not sure (anyone?). My copy of 'The Wildflower Key' (Francis Rose) lists only one for the UK - Galanthus nivalis.

The chemical Galantamine was first isolated from Snowdrops and today finds medical application in the treatment of Alzeimer's disease.

Finally a few words on Snowdrop pests and diseases, of which there are various: The RHS site describes the two fungi Botrytis galanthinae and Stagonospora curtisii as 'the bane of many snowdrop growers.' Snowdrops are also attacked by the larvae of the Swift Moth and the stem nematode worm (Ditylenchus dipsaci) (you can download a pdf file about the latter here). Prize for impressive pest has to go to the Narcissus fly (Merodon equestris) however. This black-and-yellow insect wards off predators by mimicking a Bumblebee. You can find some photo's at the insect images website. Painful as it will be to the ears of gardeners, and although I enjoy my garden's snowdrops far too much to want to see them all wiped out, as an amateur naturalist I have to say I wouldn't mind sacrificing just one or two bulbs for the chance to see one of these flies for myself!

Early Grey moth (Xylocampa areola) and Dark Chestnut (Conistra ligula)

2009-03-23T18:21:00.020Z

I am an amateur naturalist trying to discover everything that lives in my garden.

I promise that shortly I will end my minor obsession with moth postings dear readers and return to describing some of my garden's other life. For now however, two more moths caught in my new home-built moth trap.

Photo 1 shows an Early Grey (Xylocampa areola), its wings camouflaged to help it hide on trees and, photo 2, a rather tired and tattered looking moth that I think may be a Dark Chestnut (Conistra ligula) though is possibly a Chestnut (Conistra vaccinii) (My identifications come with a ‘health warning’ - I’m no moth expert and happy to be corrected). You can find better photo's on the excellent UK Moth site.

Caterpillars of the Early Grey feed on Honeysuckle, and those of the Dark Chestnut on Willow and other plants.

I learn from my copy of Moths (Michael Majerus) that the Dark Chestnut is an unusually early egg-layer amongst British moths, usually laying in March.

Sadly, beyond the facts above, I’ve been able to find very little to say about the life-styles and behaviours of either of my moths. Of course, this may be because I’ve not searched enough. If there is one thing that I have learnt from writing this blog however, it won't be because there is nothing remarkable to discover about them. As I've discovered time and again during my researches, there is an almost inexhaustible subtly and complexity in nature.

Take for example, the two butterflies, The Grayling (Eumenis semele) and the European Silver Washed Fritillary (Argynnis paphia) -

In his semi-autobiographical Curious Naturalists, a wonderfully readable account of a life spent watching and recording behaviour in birds and insects, and one of my all-time favourite natural history books incidentally, the Nobel Prize winning biologist Niko Tinbergen described some of the 50,000(!) experiments he and his team performed to gain an understanding of the behaviour of the former butterfly.

During the breeding season, male Graylings are in the habit of chasing almost anything that flutters by in the hope it may be a female. Using equipment no more sophisticated than a fishing rod 'baited' with a series of cut-out paper shapes, Tinbergen was able to reveal such facts as i) Although male Graylings are sensitive to colour (they preferentially feed on blue and yellow flowers) surprisingly, when choosing to give chase, they don't care about the colour the object fluttering by ii) Nor are they the least concerned that the ‘flutterer’ should resemble a fellow butterfly – they will happily chase a fluttering paper rectangle iii) They do care about size however; If you’re a male Grayling seeking a mate then, within reason, the bigger she is the better!

This is only the start. Once a male finally meets a female, a rich and complex courtship ‘dance’ ensues with he performing acts such as wafting scent over his partner with his wings, and gently clasping her antennae between them.

Now, in her book, Courtship: A Zoological Study (publ. Heinemann), Dr. Margaret Bastock describes some similar studies (made by D. Magnus in the 1950's) into the breeding rituals of the Silver Fritillary. Again males will chase a variety of passing ‘fluttery things’, but this time males are choosy about colour -they like best to chase yellow things.

Two butterflies, two rich and complex behaviours with intriguing differences, both only ‘decoded’ by thousands of hours of patient observation. It makes me wonder what intricate shenanigans my two moths may be about in the dead of night. (Anyone?).

Even supposing more is known about my two moths however, with more than 850 larger moths in the UK alone, not to mention 250 hoverflies, more than 450 spiders, 3200 Ichneumenoid wasps…and let’s not even think about beetles (see here), it’s certain that only a tiny fraction of what goes on in the gardens, fields and forests on our doorsteps is known in any detail.

Personally I find it both an inspirational ‘call to arms’ to we amateur naturalists to get out our notebooks and our ‘paper butterfly' experiments, but also (if you’ll permit me a slightly gloomy ending to today’s posting) a little sad to think that in one’s lifetime there will never be enough time to observe even a small part of what there is.

A March Moth (Alsophila aescularia) and The Yellow Horned Moth (Achyla flavicornis)

2009-03-21T20:44:00.014Z

I am an amateur naturalist trying to discover everything that lives in my garden.

In my last posting I described my newly home-built moth trap. I’ve been operating it for only a week, and although we’re still in chilly-March here in Oxfordshire in the U.K., I’ve already ‘discovered’ a further half dozen species to add to the seventy-five living things I’ve already reported on this blog. Normally I give each species its own posting. I’m beginning to think however, not least with summer’s ‘bounteous harvest’ approaching, that it’s likely I’ll find so many night- flying insects I’m going to need to relax this rule if I’m to stand any chance of cataloguing my garden life in a realistic time frame.

Why is it that some - although interestingly, by no means all- species of moth are attracted to artificial light? The late, great moth expert Professor Michael Majerus had a wonderfully concise answer in his book Moths (The New Naturalist Library):

“I do not know”!

A common hypothesis is that moths, some of which navigate by the distant moon and stars, are fooled into trying to navigate by the artificial light. Possibly this is the answer, but if true you might reasonably expect to see moths approaching lamps in a navigational fashion via orbital, in-spiralling flight paths. Watch a moth approach a light trap however, and I have to agree with Majerus, it’s not easy to convince yourself you’re witnessing 'navigation-in-action'. Moths often fly directly towards the light, flutter around it in seemingly haphazard ways, or seem content to settle some distance from it.

Hsaio has put forward (Jour. of Insect Physiology, Vol. 19:1971-76, 1973) an alternative theory that point light sources ‘interfere’ with the operation of moths’ compound eyes causing them to perceive regions of darkness (i.e. good places to hide) around a lamp where there are none. Again, Majerus isn’t convinced. Another of nature’s mysteries! Maybe a reader here has a comment?

To the moths themselves: Firstly, attracted to my light about a week ago, the moth in photo 1. I struggled to identify this one at first, but then caught sight of a photo of The Yellow Horned (Achyla flavicornis), in a slim photo-guide (G.Hyde, British Moths, Jarrold Colour Publications) I’ve had since I was a boy. The larvae (you can find a photo on Ian Kimber's excellent UK Moths site) feed on Silver and Downy Birch from mid-May to July before pupating to over-winter and emerge as the adults found from late-February to mid-April. I read that the Yellow Horned is a member of the Thyatiridae family of moths represented by only nine species in the U.K.

On the same evening, photo 2, a March Moth (Alsophila aescularia), the green larvae of which (again, photo's available on Ian Kimber's site) feed on many broad leaf trees including Oak, Willow and Birch. The adults fly from late February to April and over-winter as a pupae. The March Moth is notable for being one of a small number of moth species where the female is flightless. You can find a photo of a wingless female here.

Why it is that a small number of moths can ‘get away’ with having no wings, whilst all the rest expend precious energy growing them is...yep you guessed it...another of mother nature’s mysteries...at least, it is to me. Comments anyone?

Oak Beauty Moth Biston strateria

2009-03-16T17:54:00.034Z

I am an amateur naturalist trying to discover everything living in my garden.

In my last posting on the Song Thrush I introduced my home-made camera 'trap' and mentioned that this gadget was one of a number I've been cobbling together:

Ladies and Gentlemen, a round of applause please for... (photo 1) ...the Skinner/Walloon Moth Trap!

One of a number of moth trap designs you'll find on the web, the principle of the Skinner trap is simple enough: A lamp to lure the critters towards a box fitted with a 'lid' comprising two sloping sheets of plastic that don't meet in the middle (leaving a gap of about ~1inch) . The moths flutter around the lamp, land on one of the slopes and slide into the box below, whence they aren't smart enough to find their way out. A few egg-boxes give them somewhere to hide.

To best attract moths you need a lamp that peaks towards the blue/ultra-violet. Best is a mercury vapour- or so-called actinic-bulb (you need the correct electronics (a 'ballast') to power either incidentally). I bought the various bits I needed from the Entomological Wildlife Group.

And the result?

After an evening spent excitedly watching my moth trap through my kitchen window...photo 2! (In acquiring the photo, I let the moth out of the trap and it alighted on my house wall incidentally).

Twenty minutes spent flicking through my copy of Moths (Waring and Townsend, British Wildlife publishing) and I'm confident I've met an Oak Beauty (Biston strateria).

The Oak Beauty is a member of the Geometridae family of moths of which there are some 20,000 known species with 300 occurring in the British Isles. Geometridae is from the same stem as geometer and is a reference to the measuring, 'inch-worm' gait of these moths in the larval stage. The caterpillars of the Oak Beauty feed on Oak, Hazel, Alder, Aspen, Elm and Sallow. They are well camouflaged to resemble twigs. I've never myself seen one, but you can find a photo of one here.

The moth I caught was a male, as indicated by his impressively large, feathery antennae (close up in photo 2). I personally find such structures a miracle of natural engineering.

Turning to my copy of the superb Moths by (the recently deceased) Michael Majerus (The New Naturalist Library), one thing I learn about the Oak Beauty is that it has a melanic form that occurs in Holland but not in Britain.

For those unfamiliar with melanism: Much as people can differ in their eye colour and yet all remain members of the same species (human'), so some moth species can show considerable variation in their wing pattern. Within one species, some individuals might have patterned wings whilst others might have, say, matt black wings. Careful studies over decades have shown that the places where moths with certain wing patterns predominate are those places where having e.g. black wings is a recipe for good camouflage from predators (say, birds).

The increased prevalence of black winged moths of the Oak Beauty's sister species, the Peppered Moth (Biston betularia), in heavily polluted areas is an extremely famous example of supposed evolution in action (a.k.a. 'survival of the fittest') and consequently has drawn a very great deal of study and heated debate. From everything and anything convincing I've ever read however, the basic conclusion I've drawn is: it's a fact! You'll find no better, more balanced account than Michael Majerus' book above.

Finally, I can't help but end with a comment on the truly wonderful 'folk law' names of moths. The Oak Beauty, The Burnished Brass, The Twin Spot Quaker, Mother Shipton...- the list goes on an on. I commend the following link to one of my all time favourite poems: All These I have Learnt, by Robert Byron.

Song Thrush Turdus philomelus

2009-03-08T13:29:00.038Z

I am an amateur naturalist trying to discover something about everything alive in my garden.

Photo 1 shows a photo of what is, I think, my favourite garden bird, the Song Thrush (Turdus philomelus), snapped on a snowy day in February.

In case you're wondering about the piece of wood lined with seeds in the foreground incidentally, I can tell you it is the latest in the small arsenal of apparatus I'm acquiring to catalogue my garden's natural history. Ladies and gentlemen I present to you...(drum roll)...The Walloon IR-Beam-Breaker!

Photo 2 explains: Having often been frustrated at seeing a bird on my lawn that I've been too slow or too far away to photograph well, and having a modicum of electronics knowledge, I've recently cobbled together a system for automatically capturing photos. With the cable in photo 2 plugged into my camera, anything crossing the line between the two margarine tubs interrupts an invisible, (harmless) infrared beam and sets off the camera's shutter. Though its rightful place might be my dedicated robin posting, you can see a robin in photo 3 kindly demonstrating the correct technique.

Anyway, back to the star of today's posting. What I've leaned about the Song Thrush (Turdus philomelus), has mostly come from the pages of Eric Simms British Thrushes (New Naturalist Series).

Thrushes are a large, globally distributed genus that includes the blackbird, the American Robin and the Ring Ouzel (an occasional visitor to the UK and perhaps the bird I'd most like to see incidentally).

Song Thrushes average about 32cm long and 74gm. The feathers on their back are a warm brown and they have a creamy-white, speckled breast. (The superficially similar Mistle Thrush (Turdus viscivorus) is about 4cm longer and has a whiter breast). Song Thrushes have a characteristic direct flight, easier seen than described (Mr Simms quotes speeds of around 48kph).

Song Thrushes breed from early March through to July and moult in July. UK birds typically do not migrate any great distance, though birds that do, do so around October.

Song Thrushes have a lovely piping voice (you can hear a clip on the RSPB site). Their repertoire can include imitations of other birds and supposedly even car alarms and the trilling of mobile phones. Singing peaks around April/May, when birds are most active in breeding and defending territories. One physiological trigger for singing is temperature: Mr Simms describes his own careful observations on how singing in his garden thrushes correlated with ambient temperature and also mentions that some researchers have induced premature singing in thrushes in winter by artificially raising the temperature.

In a study of territorial behaviour in Oxford, male/female pairs of Song Thrushes were observed to hold territories of around 150feet square during the breeding season. During winter, most territories were held by solitary males, though occasionally one would be held by a solitary females. (No doubt there's enough ecological complexity underlying this behaviour to motivate a whole PhD's-worth of research, if indeed such a study hasn't already been done).

It's not uncommon on a country walk here in the UK (does this happen elsewhere?) to hear the 'tap tap' of a Song Thrush engaged in the business of removing the shell of a snail by smashing it against a rock ('a thrush's anvil'). You can find some video footage on the RSPB site. Interestingly, Mr Simms says that snails tend to be a last resort food for Thrushes - their preference being worms, insects and berries (including those of Holly, Ivy, Yew, Honeysuckle and Hawthorn). Something I had not hitherto known was that Song Thrushes will forage on shorelines where they've been recorded feeding on periwinkles, dogwhelks and sandhoppers.

I'll close with a personal comment: For me much of the fascination and enjoyment of natural history comes from trying to acquire a smattering of 'scientific' understanding about my garden's life. At the same time of course, like everyone, I have an emotional response to the things I see. Actually however, in the case of garden birds, although I find them wonderfully formed and love to hear their singing, I personally don't find them 'cute' or 'charming' in the way I think some people do. I've heard the idea that birds evolved from dinosaurs ("dinosaurs that grew feathers"). The scientific truth of this is hotly disputed and I don't know enough of the debate to knowledgeably comment, but watching blackbirds scurrying around on my lawn, for me there is more than a passing resemblance to a hunting pack of miniature Velociraptors! No one's said it better than English poet Ted Hughes in his poem Thrushes

Terrifying are the attent sleek thrushes on the lawn,
More coiled steel than living - a poised
Dark deadly eye, those delicate legs
Triggered to stirrings beyond sense - with a start, a bounce,
a stab
Overtake the instant and drag out some writhing thing.
No indolent procrastinations and no yawning states,
No sighs or head-scratchings. Nothing but bounce and stab
And a ravening second.

Haematoccus algae

2009-02-28T09:09:00.032Z

I am an amateur naturalist trying to learn a little about everything living in my garden.

Recently, in the interests of finding some life-form with which to entertain the legions of avid readers of this blog (hem, hem), I decided to investigate what life might exist in a small pool of rainwater that had collected in the crevices of a sheet of polythene lying in my garden. Putting a drop under my hobbyist's microscope I was immediately confronted by large numbers of the creature seen in photo 1 (scale:1 small division = 1um). Some were motionless. More excitingly, others were highly active, 'zooming' through the water at a rate of knots (see later)

Some internet searching later, and with the help of photo's such as those on Ralf Wagner's microscopy site, and I'm tolerably confident I'm looking at a Heamatoccus alga.

The red colouration, motile behaviour and the presence of the transparent, gelatinous envelope surrounding the central green body all fit with the the species being H. pluvialis on this site ('Algaebase') . I don't claim any certainty over this identification however, since firstly I'm no expert, and secondly the same site lists 5 other species in the Haematoccus genus and a staggering 123,336 species of algae overall.

The family Haematoccae is part of the Volvocales order of algae, one example of which - Volvox - is a perennial favourite with microscopists. The Volvocales are equipped with two whip-like flagella - the secret to their ability to 'swim' through the water. The length and positioning of any flagella on an alga is an important aid to identification. Unfortunately the quality of my camera/microscope optics doesn't appear to be good enough to have caught these in the (dormant) Haematoccus specimen in photo 1 (or is it that flagella are lost in the dormant state?) - but the superb photo's by Wim van Egmond here show them clearly.

In researching the life in my garden I constantly come across what I imagine at first to be 'obscure' creatures. "Beyond naming it, surely no-one can have found the time to learn anything interesting or remarkable about this little critter!" I think to myself. It's a constant source of enjoyment to me to learn I'm wrong, and that for just about anything I come across, someone somewhere will have discovered some remarkable or interesting 'story' (which isn't to say that vast amounts don't remain unknown about the natural world of course).

So it was with H. pluvialis. Beyond a few dry descriptions in an obscure journal, surely there would be nothing say? Wrong again! It turns out H.pluvialis is an algae of significant commercial importance. It produces the highest known concentrations of astaxanthin of any living creature and is cultured on a commercial scale. Astaxanthins are chemicals used in the cosmetics, food and feed industries. They are antioxidants and have been studied for their potentially beneficial effects against everything from cataracts to colonic cancer. Guerin et.al. have produced a review (Trends in Biotechnology, 21(5), 2003). Astaxanthins are cartotinoid chemicals responsible for the red coloration in photo 1. They act as a 'sun block' against harmful UV rays. Those dormant algae I observed in my microscope sample seemed to contain more red pigment than mobile ones. I assume this is because dormancy is, in part, a mechanism to survive in dry conditions when cells can expect to need more protection from the sun.

Algae introducing astaxathanins into the food chain is the reason why animals higher up like shrimps, salmon and flamingos end up with pink flesh or feathers.

Returning to the issue of the mobility of H.pluvialis, Burchardt et.al (Biodiv. Res. Conserv. 1-2, 163-166, 2006) give a figure for their swimming speed of 200m/h. Given that their size is about 20um, scaling this up, and assuming a human about ~2m tall and I've got my maths right, this corresponds to a person swimming along at 20,000 km/h!

Finally, I can't end without mentioning one of the few books I have that gives a fairly detailed introductory guide to freshwater algae, namely Freshwater Microscopy by W.J. Garnett. Though it contains no real information about Haematoccus beyond a mention, it covers many common UK species in some detail. First published in 1953, I particularly like dipping into it for its evocation of a seemingly quieter more 'holistic' (for want of a better word) world, before out-of-town shopping centres and a life of frenzied commuting up-and-down packed motorways, when armies of amateur hobbyists seemed to spend their evenings and weekends learning the art of painting watercolour landscapes, investigating the geology of their county, or studying the lifeforms in their village pond. Or perhaps that's rose-tinted nonsense, though I do wonder how many hobbyists there are today, who, of a typical weekend, boil hay in rainwater in order to culture pond protozoa for study as Mr Garnet advises!

On the other hand I may be entirely wrong and there are legions of you hay-boilers out there! If you're one such, do leave a message to say hello.

Common Pheasant Phasianus colchicus

2009-02-14T09:03:00.032Z

I am an amateur naturalist trying to discover everything living in my garden.

Handsome fellow isn't he! Photo 1 shows one of two male Common Pheasants (Phasianus colchicus) that visited my garden recently. Living as I do in rural Oxfordshire, meeting one isn't unusual; their rearing and shooting is common hereabouts.

The RSPB estimates there are 1.8million breeding female pheasants in the UK.

From a search of the internet a few random facts I've turned up about pheasants include some evidence that pheasants are sensitive to noises beyond the range of human hearing (Stewart, The Ohio Journal of Science. v55 n2 (March, 1955), 122-125). Secondly, given a choice, the 'stuff' (sand, loam, straw, feathers...) in which an adult pheasant will choose to take a dustbath can be predicted ahead of time by noting the material a bird prefers to peck at when still a chick (Vestergaard&Bildsoe, B Acta Vet. Brno, 1999,68, p141). This may seem an esoteric piece of knowledge, but as anyone who has ever watched a documentary about battery chickens will know, feather plucking is a damaging problem among livestock birds under confined conditions and an understanding of pecking behavior in birds can have worthwhile commercial implications.

The Common Pheasant is native to Asia. Like the peacocks, the Common Pheasant is an example of a sexually dimorphic species - a species in which males and females show consistent difference in form. Male pheasants are brightly coloured; Females are cryptically camouflaged. Photo 2 shows a female I spotted lurking in my garden shrubbery early last summer.

Sexual dimorphism is a much studied topic in the theory of evolution. Scientists would like to understand more deeply what forces encourage it and what advantages follow.

An internet search led me to a number of papers on sexual dimorphism in pheasants but unfortunately most were on the pay-to-view sites of commercial publishing firms. This always irritates me as it's typically you and I, the taxpayer, that has paid for the research contained in these papers. To be asked to pay again to read the results seems a bit much! Anyway, I did manage to find a few freely available papers from which I learn that female pheasants choose male mates based, in part, on the length of their spurs. Studies have shown spur length to be an honest indicator (see my peacock posting) of male health - males with longer spurs really do seem to be fitter than less well endowed males.

Spurs are a secondary sexual characteristic - a characteristic that differs between the sexes.

Girl pheasants also appear to judge their men folk according to the quality of their wattles (the red cheek patches in photo 1). Smith et.al. provide one study of this. My (amateur) understanding of their work is as follows:

Biologists had previously worked out that certain 'carotinoid' chemicals were associated with coloured appendages in some animals. At the same time, animals getting a good diet were known (perhaps unsurprisingly!) to have stronger immune systems than poorly nourished specimens. Smith et.al. wondered whether carotinoids were the root cause of both i.e. whether both the strength of a male's disease immunity and their wattle quality were directly controlled by the amount of carotinoids in their diet. If so, this might provide a very natural explanation of why females have 'a thing' for wattles -good wattles would be an honest indicator of the disease resistance of a suitor.

And the answer...after a series of detailed experiments Smith et.al. found no such correlation! Back to the drawing board in terms of discovering the deeper explanation of what's going on, but a nice example for those who might question whether science isn't ultimately a process of rigorous enquiry.

A lichen Aspicilia calcarea

2009-02-08T10:16:00.028Z

I am an amatuer naturalist trying to discover what lives in my garden.

Those following my recent posts will know I have been on something of a mission to blog the lichen-life on the exterior of my house. Photo 1 shows yet another inhabitant - another crustose lichen (for those unfamilar with lichens, see my post here).

Incidentally, photo 1 also captures (upper left) our old friend, the moss, Tortula muralis.

After a little research I'm confident the lichen here is Aspicilia calcarea. Characteristic features include the cracked, white thallus (the main body of the lichen) and the irregularly shaped apothecia (the black, spore-liberating cups) sunk into the thallus. The books tell me that A. calcarea is common on hard calcareous walls etc. in lowland Britain. Photo 2 shows a closeup.

For those wanting a cheap photographic key to some common, British, urban lichens incidentally, I recommend the short-form guide sold by the good people of the Field Studies Council . For something more detailed the book Lichens (Frank S.Dobson) is especially good.

I'm fond of lichens. Their ability to shrug off the worst the elements can throw at them gives them, for me, an appealing minature 'feistiness' - I picture them squatting on exposed boulders on windswept mountain sides goading the rain "Come on! Give me your best shot! Is that all you've got pal !?"

On a more rational note (!), something that intrigues me is the diverse array of colours and shapes lichens adopt. I have no deep expertise in evolutionary ecology but as I understand it, there is nothing haphazard about the forms taken by species. Life is hard and an ever-present scarcity of resources and the threat of predation and disease is a constant imperative, forcing species to individually specialise in unique methods of suvival. A famous example is of course the beaks of finches, with different species having been driven to evolve different beak-shapes to allow them to eat different nuts and seeds. Different birds evolving different beaks to help them occupy different feeding niches is one thing. The distinct environmental pressures or purposes that drive two lichens such as A. calcerea and C. citrina to adopt such different colours and (once you look closely) really quite different textural forms, when both seemingly occupy the same ecological niche of lowland stone (indeed, the same household windowsill in my case!) - I struggle to guess. Do leave a comment if you can help me.

European Hornet Vespa crabo

2009-02-02T12:02:00.029Z

I am an amateur naturalist trying to learn something about everything alive in my garden.

Photo 1 (click to enlarge) shows the handsome insect I found lying dead on a windowsill in my house some months ago. I am not expert at insect identification so at first I wasn't sure what I was looking at, but a little internet browsing and I'm confident I've found a European Hornet (Vespa Crabo): of the half dozen-or-so social wasps one might encounter in a British garden, the hornet is the only one with a distinctly brown coloured thorax. Much the most extensive introductory source I've come across online is Dieter Kosmeier's excellent hornet website.

Despite their fearsome reputation hornets are no more likely to attack humans than other wasps, nor is their sting notably worse. They are voracious predators of other insects however; a nest colony can take up to half-a-kilo a day. There are even records of hornets taking down pairs of copulating dragon flies (see Dijkstra et. al., Int. J. of Odonatol. 4(1),17-21, 2001).

Queen hornets hibernate over winter - the site of the Bees, Ants and Wasps Recording Society gives a record of a queen discovered beneath a rotting branch of cherry wood. She emerges around May and begins the process of constructing a nest and egg laying. By mid summer the nest is in full swing and may contain in excess of 500 individuals. Nests of one species of hornet (Vespa wilemani) have been recorded at altitudes of 2300m (Martin, Jpn.J.Ent.61(4), 679-682,1993). Come winter the nest is permanently abandoned (hornets do not reuse a nest the next year).

Figure 2 (click to further enlarge - if you dare!) shows a close up of my hornet's feasome jaws and, atop the head, the circle of small primitive light sentive 'eyes' (ocelli). Counting the number of segments on the antennae (=12) tells me my hornet is a female (males have 13)

A debate amongst professional naturalists concerns the mechanism and role of 'brood policing' in Vespa crabo. In brief the debate surrounds the question of why only the eggs of the queen, and not of the workers, are allowed to hatch (I was surprised to learn that the workers are not in fact sterile, and are quite capable of producing progeny). In the 60's the British evolutionary theorist W.Hamilton, argued mathematically that, other things being equal, in order to benefit their gene-line organisms ought to behave in ways that favour their close relatives (kin). Genetically however, a Vespa crabo worker is closer to its own offspring or indeed the offspring of a fellow worker than that of the queen. Despite this, workers ruthlessly seek out the eggs of fellow workers and discard them. Foster et.al. argue (Molecular Ecology (2000) 9, 735-742) that this may be due to the queen chemically controlling the 'minds' of the workers, hence the title of their paper 'Do hornets have zombie workers?' - although overall the jury seems still out.

Or at least that's my loose understanding of things. As I say often, I'm not a professional. I'm happy to be corrected and in particular I've not managed to follow the quantitative aspects of this debate. For example, Foster et. al. begin:

"In a colony headed by a singly mated queen, workers should prefer rearing sons (r= 0.5) and other workers’ sons (r= 0.375) to their mother’s sons(r= 0.25)'

I get the general idea, but can anyone give me a simple explanation of what these numbers mean and how they're calculated?

A lichen Caloplaca citrina

2009-01-17T12:59:00.013Z

I am an amateur naturalist trying to discover everything living in my garden.

I've previously blogged the yellow lichen Xanthoria parietina that grows on the upper, east-facing exterior window sills of my house. On the lower sills there's another yellow algal/fungal partnership taking place (photo 1 - click to enlarge), this time in the form of a crustose, Caloplaca lichen.

I'm not a lichen expert, but having referred to the text books, I'm fairly confident the species here is Caloplaca citrina. The apothecia (the little, yellow spore-producing 'pin cushions') are spread about over a powdery, yellow thallus. Were this C. holocarpa (another common Calopaca with yellow/orange apothecia) the thallus would be grey. The thallus of C. dalmatia is cracked by thin black lines. The lack of any change in lichen texture / colour near the perimeter of the patch also distinguishes it from other various other superficially similar Caloplaca species such as C. decipiens. Identifying lichen is all about noting the tiny details!

There is yet another common possibility: the superficially similar powdery, yellow lichen Candelariella vitellina. In this case however there is an acid test (if you'll forgive the (chemically imprecise!) pun) to tell the two apart: a tiny drop of potassium hydroxide applied to most Caloplacas will turn them red. Candelariellas on the other hand, show no reaction. Photo 2 shows the positive result in my case.

I've read a suggestion that the purpose of yellow colouration in lichens is to provide protection against the harmful UV part of sunlight. I'm happy to accept this but it makes me wonder why only some lichens need to bother (there are plenty that don't: green, grey, white and even black lichens being commonplace - the two Verrucaria lichens I've previously blogged for example) .

Finally, the fact that C. citrina occupies the lower sills or my house and X. parietina the upper ones, makes me wonder whether the latter is more tolerant of low light conditions. Can anyone tell me?

Coal Tit Parus ater

2008-12-08T21:11:00.019Z

I am an amateur naturalist trying to teach myself something about everything alive in my garden.

Taken on the same morning as my Blue Tit photo, photo 1 shows a Coal Tit (Parus ater) on my garden birdfeeder.

Averaging around 9-gm, Coal tits are the smallest British tit and easily recognised by their black crown and the white patch at the back of their head: No other British tit has the same. They are common in the UK, often inhabiting conifer woodland, the RSPB website giving the number of breeding pairs as 653,000.

What other I know about coal tits I've learned from reading The Titmice of the British Isles (John A.G.Barnes, publ. David&Charles 1975), this includes the rather charming fact that once mated a male-female pair will tend to remain bonded across the years, assuming both manage to survive that is; Annual mortality for coal tits is around 80%.

I was surprised to learn that coal tits make their nests very near to ground level in tree stumps or even in holes in the ground. I've spent many hours walking through woodland and don't recall ever having seen one, which I suppose must mean they're well concealed. Females lay on average 9 eggs around April-May. Coal tits are diligent parents and have been recorded making upwards of 60 visits to the nest in a single day to feed their chicks.

Coal tits spend a great deal of their day - around 90% - feeding. Given their small body size and slender beaks they consume the smallest insects (typically 0-2mm according to the book above) among the tits, an example of evolution driving different species to specialise in different feeding habitats and foodstuffs to best survive in one another's company. An exception to the rule is beech mast, which is so plentiful in Autumn that many different tit species come together to enjoy the glut.

Something I didn't know is that coal tits will sometimes store food (seeds etc.) for later consumption. Typical hiding places might be holes or under moss on tree trucks. There is a record of one bird digging up a seed that it had hidden more than a fortnight previously.

Finally, I have often wondered about the time at which birds go to bed. Of course 'late in the day', but is that as light is dimming, or say, a little after sunset? Dr. Barnes' book has answered my question: the coal tit is on average an early rooster, typically abed 1.7 minutes before local sunset. Good night!

Blue Tit Parus caeruleus

2008-12-06T22:16:00.046Z

I am an amateur naturalist trying to learn something about everything living in my garden.

Some of you may recall that in my posting on White Tipped Bristle Moss I mentioned being impressed at the performance of the camera I was fortunate enough to borrow on that occasion. Well, I'm pleased to announce that the birthday fairies have since visited and I am now the proud owner of a fancy digital SLR. I offer this in explanation for why I have spent the greater part of Saturday morning, crouched in a 'birdhide' (a.k.a my garden shed!) my zoom lens trained on my garden birdfeeder.

Blue Tits (Parus caeruleus) are small birds (around 11gm, 11cm), easily recognised by the yellow breast, black eye stripe on a white face, blue crown, and blue and green dorsal (=viewed from back) feathers (photo 2 - click to enlarge). With experience (which I don't have!) it's apparently possible to distinguish males from females by the slightly smaller size and less vivid colourings of the latter.

The Blue Tit's call is a high pitched 'tsee-tsee-tsee' or occasionally a scolding 'churr'. They are one of Britain's commenest birds: The RSPB website gives the number of breeding pairs in the UK as approximately 3.5million.

According to my copy of The Blue Tit (Jim Flegg, Shire Natural History) female Blue Tits normally lay a single batch of between 5- and 16-eggs, during March or April. As with Robins, life is hard, and annual mortality in Blue Tits is around 90%. I had not hitherto realised that predators of the chicks include the Greater Spotted Woodpecker. Late summer and autumn see the highest mortality rates. More happily for my blue tit, birds that make it into Winter have a decent chance of reaching the Spring.

During Spring male Blue Tits defend terretories. During Autumn these break down and Blue Tits join large flocks of small birds roaming the hedgerows. During Winter a sort of 'half way house' emerges with birds forming smaller flocks and confining their travels to smaller (300-400m^2) areas. Again, like Robins, UK Blue Tits tend not to travel any great distance during their lives, <1% moving more than 100km although every few decades climate conditions lead to mass influxes ('irruptions') of birds from the European mainland.

A puzzle about Blue Tits, described in the book above, relates to their dietary fondness for Winter Moth (Operohtera brumata) and Tortix caterpillers. In some years in Oak woodlands, these attain epidemic proportions. Blue Tits seem able to predict (or to state things less anthopromorphically - there is a correlation between) when, and how many eggs to lay to take best advantage of the arrival of the caterpillers. How they do this isn't known, or at least wasn't when the book was written.

Finally, a fact well know to Brit's of a certain generation, which I include here for the interest of overseas readers, was the tradition (now rendered largely extinct by the ubiquitous supermarket) of having milk delivered to the doorstep in glass bottles capped with aluminium foil. It was to a national hazard to find Blue Tits had pecked through the foil to get at the cream below. You can find a photo of this here. Charming at first, but the householder soon learnt to leave empty youghurt pots out for the milkman to place over the bottles to thwart the theives!

Trochila ilicicola A fungus on holly leaves

2008-11-12T20:48:00.033Z

I am an amateur naturalist trying to learn a little about everything living in my garden.

For those of an inquisitive disposition, one of the wonderful things about natural history is its ability to generate an inexhaustible supply of questions one doesn't need to be a professional to either ask or investigate: Noticed something alive!? O.k., so what is it?...and what does it eat?... what eats it?...when does it mates, how does it mates?...You get the idea.

To supply a germane example: In a previous posting on my garden's holly tree, I reported being struck by the small number of creatures reported to derive nourishment from holly's tough and spiny leaves. This started me wondering about what creature might surmount the seemingly even tougher problem of eating dead holly leaves...

...photo 1 (click on photos to enlarge) shows a holly leaf I found in the leaf litter beneath my tree. Photo 2 shows a 100x magnified version of some of the small black dots decorating the surface upper-centre, and photo 3 some of the larger ones covering the remainder of the leaf.

It's perhaps no surprise to learn that the agent of decay of dead holly leaves is a fungus. Fungi are separated into two great divisions ('phyla'), the basidiomycota (=most of the familiar 'mushrooms') and the ascomycota which are typically small, cup shaped fungi (see a previous posting for more details). Clearly photo 2 shows my fungus to be one of the latter. The cup's inner surface (hymenium) is the site of spore production.

In the case of my holly-leaf, a little web searching (specifically of the encyclopaedic bioimages site) suggests the species of fungus at work is Trochila ilicicola. (A smaller question I do have however, is whether the two types of black spots - the smaller dimples of photo 2 , and larger pustules of photo 3 - might conceivably be two different species. Can anyone comment?)

I'm led to understand my cup fungus has a rather neat trick up it's sleeve, namely a hinged lid which it can open when conditions are damp (and hence good for liberating spores), and close when conditions are dry. I didn't get the opportunity to try observing this under the microscope, but you can find some photos on the fine mycolog site.

So there you have it. The next time you take a walk on an late autumn day when interesting natural history might seem in short supply, try picking up a dead leaf!