Saturday, September 19, 2009

Common Wasp Vespula vulgaris

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!

5 comments:

George G said...

What a fantastic site, in subject, quality, and intent! I've never seen such an expression of analytical clarity, wonder, and economy -- all found within one's yard. Thank you for your efforts, Mr. Walloon; they enrich us all.

Might you share something of the photography and microscopy you use? I'm fascinated by your photos with the microscopic measuring scales.

George Goldsmith
Watching plants in and around Diamond Bar, California, USA
g_goldsmith@hotmail.com

George G said...

What a fantastic site, in subject, quality, and intent! I've never seen such an expression of analytical clarity, wonder, and economy -- all found within one's yard. Thank you for your efforts, Mr. Walloon; they enrich us all.

Might you share something of the photography and microscopy you use? I'm fascinated by your photos with the microscopic measuring scales.

George Goldsmith
Watching plants in and around Diamond Bar, California, USA
g_goldsmith@hotmail.com

Maggie's Devon nature blog said...

Thanks for that - I'll look more closely at wasps on our own apples now. Great pic of the wing. Wasps seem particularly to like figwort in our garden, but only at the end of summer. And I'm told, though I haven't tried it yet, that a bunch of mint on your picnic table will see off the wasps. Not that anyone's been stung yet. We had a nest in the roof of a previous house, and when the colony died in the winter there would routinely be 30-40 dead wasps by the window of the spare room of a morning - but still no-one got stung, even my mum who continued to sleep in there!

Henry Walloon said...

George

Many thanks for the kind words of encouragement. I'm pleased to meet a fellow plant watcher.

My microscope and photography methods are rather humble! I have a modestly priced student microscope (a Wesbury SP30). An optional extra was to buy an eyepiece that has the microscopic measuring scale built in. To take microscopic photos I simply hand-hold a small Olympus 'point and click' digital camera up to the eyepiece and snap away.

For more general(i.e. non-microscope) photography I did recently splash out on a more expensive digital SLR camera (a Canon EOS 450D). I've had the occasional kind comment about some of the photo's I've taken with it but once again I wouldn't claim to possess any real photography skills. Rather, the wonders of digital storage permit my 'brute force' approach of simply snapping several dozen photo's of a subject in the hope that one or may turn out to be of reasonable quality!

Henry Walloon said...

Maggie

Thanks for dropping by again and your nice comments.

Mint heh? I shall give it a try and let you know how I get on! (Though like you, I can't complain about any actual stings at my garden picnic table).