A Hoverfly, Syrphus ribesii

I am an amateur trying to learn a little about every creature in my garden.

I recently blogged the blooming of the California poppies in my garden, and it was on one such flower that I found the hoverfly seen in photo 1 (click to enlarge).

For the amateur naturalist attempting to decide which of the 250 British (or worse, several thousand global) species of hoverfly you are looking at, an obvious first problem is how do you know you're looking at a hovefly at all, as opposed to any of the much larger class of non-hoverfly flies? The answer is easily stated, though perhaps not so easily observed in the wild: hoverflies (family Syrphidae) are distinguished amongst the flies (order Diptera) by the presence of a vein that runs along the edge of the wing together with a so-called 'false vein' running along the wing's length. Houseflies, for example, have neither. I don't have access to fancy photographic software, but in photo 2 I've done my best in to enlarge and highlight these features for the hoverfly in the photo above.

The above facts, and just about everything else I've learnt about hoverflies I've garnered from the excellent Hoverflies (Francis S. Gilbert, publ. Richmond, 1993). This book, written for the amateur naturalist, contains a wealth of detailed but easily digested information. It also contains some beautiful colour plates, by which I believe I've identified my hoverfly as Syrphus ribesii (I haven't found a common name. Anyone?).

Hoverfly adults visit flowers to feed on nectar and pollen, the latter as it contains necessary carbohydrate (typically about 25%; nectar has none). It's believed that hoverflies select flowers mostly on colour (rather than e.g. scent). Yellow seems a particular favourite. Whilst the adults may be peaceful vegetarians, the larvae of S. ribesii are aphid predators.

One of the impressive abilities of S. ribesii is its ability to regulate it's body temperature somewhat by vigorously 'flapping' its wings whilst remaining perched. On cold mornings, the 'whine' of S. ribesii males can be heard in woodland as they seek to build up body heat, driven by the urge to get airbourne and seek females. It is apparently even possible to hear the pitch increase as their body temperature rises- like a jet engine powering up - something I'm determined to listen out for.

A particularly inspiring feature of the book above is that the author tabulates a whole series of unanswered hoverfly puzzles of genuine scientific interest to the professionals, yet simultaneouly fully amenable to study by the amateur: "Do predators such as wasps take feeding hoverflies. How risky is feeding is feeding at different flowers?"; ""Is there a definite [hoverfly] courtship? What is it like? How long does it last?"and a dozen others. I personally find it inspiring to know that even in the household garden there is a complexity that exceeds our current best understanding, and yet may require no more than patient observation to unlock its secrets.

Horray for the humble hoverfly!

Heartsease pansy Viola tricolor

I am an amateur naturalist attempting to find out something about everything in my garden.

Spreading their way along the front flower-border of my garden are numerous little Heartsease pansies (Viola tricolor). Photo 1 (click to enlarge) shows a solitary plant flowering in early April and photo 2, taken more recently, a patch of its joyously sprawling compatriots enjoying Oxfordshire's recent combination of warm, wet weather. As was the case for the California poppies I wrote about recently, I am in no doubt about the identify of these plants since it was me that grew the first of them from a packet of seed some few years ago.

A tough little creeping perennial, Heartsease is the wild ancestor of the myriad cultivated pansies you can find in your local garden centre. As I learnt from reading the site of the American violet society, amongst the first persons to take a horticultural interest in Heartsease was the British Admiral Lord Gambier (1756-1833) who, when he wasn't battling the Napoleonic fleet, was busy with his gardener William Thompson, breeding the first hybrid pansies. I have to say that I prefer the original, but each to their own!

From my copy of The Englishman's Flora (Geoffrey Grigson, publ. Paladin) I learn that there are dozens of alternative names for my pansy, including the poetic Love-In-Idleness the name used by Oberon in Shakespeare's A Midsummer Night's Dream (Act II, scene 1) when he describes the power the flower has as a love potion:

And maidens call it love-in-idleness
Fetch me that flower; the herb I shew'd thee once;
The juice of it on sleeping eyelids laid
Will make or man or woman madly dote
Upon the next live creature that it sees.

Can anyone out there tell me if this works?!

A name that doesn't get a mention in the book above is 'Johnny Jump Up', the name used in the U.S. I understand.

V. Tricolor is a member of the (approximately four-hundred strong) Viola genus of flowers. The rather asymmetrical (the technical term being zygomorphic) arrangement of the five petals is believed to make it an example of a highly evolved flower. The streaks on the lower petals are supposedly there to act as nectar guides for pollinating insects, these being (in the Netherlands at least, according to a scientific paper I came across by Veerman and Zon, 1964) mainly bumblebees and the Silver 'Y' Moth (Plusia gamma).

There are some excellent sites (this one for example) on the internet describing the botanical details of flower structure. The name and purpose of one structure has eluded my (decidedly non-expert) attempts to identify it however, namely the two white 'lips' that can be seen in the centre of the flower in photo 1 (click to enlarge). Under magnification (photo 3, 40x) these remind me of white-tentacled sea-anemones. No doubt an embarrassing display of botanical ignorance, but can anyone tell the name and purpose of these curious structures?

A fungal rust Puccinia lagenophorae

I am an amateur naturalist trying to find out what lives in my garden.
I ended my most recent posting by saying that that a certain "elderly gentleman" had taken up residence in my garden and that he was not in the best of health. Photo 1 (click to enlarge) shows one of his leaves and the rusty brown patches afflicting it.

I know almost nothing about plant diseases, but a short time spent searching the Internet for diseases on groundsel convinced me that the cause of the brown patches on the leaves is Puccinia lagenophorae, an example of a fungal rust.

A close up (photo 2, 40x magnification) shows the cup-like fungal craters produced in the leaf. I believe these may be what are technically termed the rust's spore producing aecidia.

The technical name for the rusts is the Urediniomycetes. From my copy of Fungi (Spooner and Roberts, Collins NN, 2005) I learn there are about 7000 species worldwide and 260 in Britain of which 14 are new here since 1966, suggesting there are still more to be discovered. They have a complex and fascinating life cycle, though one rather alien to us. They can go through periods of sexual cross-fertilization in which they exude nectar-like liquids to attract "pollinating" insects, other periods as airborne spores and still others as thick-walled teleutospores designed to lie dormant over winter and germinate in the spring. Some parasitise different plants at different points in their life cycle, changing their form and appearance as they do so. This site has some more details. I find it wonderful to think that such intricate and complex patterns of life are carrying on quietly in the little places of my garden.

Puccinia lagenophorae has an interest all of its own: it is a relative new comer to the UK having arrived here from Australia only in the 1960's (it was first recorded on groundsel in Dungerness in Kent in 1961). Until recently it was unknown in the US, but is apparently now making an appearance there also. P. lagenophorae's ability to attack groundsel - an agricultural weed - has led to it being investigated as a 'biological weedkiller'. Marigolds and Oxford Ragwort may apparently also be attacked

Finally, one thing I'm not clear about from my reading is how terminal infection is for my plant. Is my weed almost certainly 'doomed' or is it more akin to him having caught a bad cold? If someone out there can tell me, do please leave a comment.

Groundsel Senecio vulgaris

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

Growing in my garden behind my house - at (0.1,1.5), see here - I found the weed seen in photo 1 (click on it to enlarge). A quick look in a wildflower book and the curiously compact yellow flower heads (the flowers are fully mature in the photo, not unopened as a first glance might suggest) enabled me to easily identify it as Groundsel, Senecio vulgaris. The form of the flower head is what botanists term " a rayless capitula" (a capitula being the term for a head composed of many indiviual, bunched flowers -dandelion heads are another example).

According to my copy of The Englishman's Flora (Geoffrey Grigson, Paladin, 1975), the word groundsel derives from the Old English grunde-swilage: literally 'ground swallower' - a reference to the plant's ability to rapidly colonise newly cultivated soil. The Latin name Senecio, is thought to come from senex meaning 'old man' - a reference to the plant's white head of 'hair' (the seeds) which over time fall out exposing a little bald white head! A charming analogy I'm sure you'll agree.

Although groundsel does find mention in herbal medicine (Culpepper mentions its use in inducing sweats and as a purgative), in common with other members of the daisy family, it contains numerous unpleasant chemical compounds and is best regarded as highly poisonous to humans. The black-and-gold striped caterpillars of the Cinnabar moth are very fond of it however.

A search of the internet led me to the discovery that my humble weed has quite a degree of fame in the scientific community: In 2003 botanists Dr's Abbott and Lowe published a scientific paper describing a weed that Dr. Abbott had found growing wild at the edge of a car park in York twelve years previously. The paper showed that the plant was a fertile cross between groundsel and another British plant, Oxford Ragwort. This made it only the sixth new species of plant to have been discovered in Europe and North America in the last century. More remarkably still, since this new species was believed to be less than 50years old, finding it marked not just the discovery but the very emergence of a wholly new living species within our lifetime! (See this article for some colour photos).

Oxford Ragwort has its own marvellous story incidentally, having been introduced from Sicily to Oxford University's botanic gardens in 1690, whence botanists recorded its systematic spread over much of the UK over the next two hundred years. Being a plant indigenous to the cinder-strewn volcanic slopes of Sicily, it was aided in its march by the emergence of a network of cinder strewn railway lines in Britain at the time.

Some of you may recall that in a previous posting I wondered whether a careful study of a magnified view of a dandelion seed would allow you to tell apart the 235 sub-species of dandelion. I still don't know the answer, but certainly the seeds of groundsel (photo 2 - click to enlarge) and dandelions are quite different, with the pappus (the 'feathery bit') connecting directly onto the achene (the seed body) in groundsel, whilst for dandelions (or the one I found at least) the two were separated by a thin stem.

The knowledge of groundsel's importance in evolutionary biology and its charming image as a little old man, left me with rather a soft spot for my humble weed. Unfortunately, as you will shortly read, this little old man was not in the best of health...