Friday, 10 November 2006

The sting is the tail

I spotted this wasp in a garden bed at work. It's either an ichneumon or a braconid. (I'm still not up to speed on wasp systematics but maybe Amegilla can narrow it down.) Either way, it's a parasitoid, one of those wasps with the grisly and fascinating life cycles.

The female lays her eggs on or in the host, using the long ovipositor to position them just so. The host remains alive, which means that the larva is living in a larder that never runs out of fresh food.

These wasps have several interesting adaptations. There's that whopping great big ovipositor—the hypodermic needle at the rear end—which penetrates the host's exoskeleton and deposits the eggs with surgical accuracy. And the underside of the abdomen is less heavily armoured than in other types of wasps, so it is extremely flexible. This helps in egg-laying. For a similar reason, the legs also have an extra joint, so the wasp can raise its body high over the host.

They 'parasitise' a wide range of species and are not above attacking their cousins, the sawflies.

Ha! Alien schmalien.

3 comments:

AYDIN ÖRSTAN said...

Glad they don't come looking for humans.

amegilla said...

Good spotting and a great captue. They're flighty little beasts and can be frustrating to photograph.

To differentiate a Braconid from an Ichneumon you have to engage in the preposterous activity of attempting to locate an extra wing vein in the forewing.

If you don't feel like deep freezing the animal and examining it under glass, you can fool yourself into thinking you've almost got it sussed - and then it turns out to be a Gasteruptid.

I now call them all Brachneumons. Or Ichonids. Works for me.

Snail said...

They're rather speccy, aren't they. I've seen this species or something resembling it around my garden. I've never been game enough to try to catch one in a jar. I know my limitations.