Wednesday, September 01, 2010

Cousin wasp

We found this wasp climbing up a window in Tim Horton's. Laurie dug a pill bottle out of his pocket, and I popped her inside.

An Ichneumon wasp, Pimpla sanguinipes, female.

At home, she gave me all sorts of trouble, refusing to sit still, even for a second. Even after a time-out in the fridge, she revived instantly and started to race around. I got a few blurry photos, decided that's as good as I was going to get, and put her outside.

She immediately flew over my shoulder, back into the house, and disappeared. Half an hour later, she turned up on an air cleaner behind my computer, and puttered around, stopping every now and then to contemplate the camera. Silly bug!

She's an ichneumonid; a parasitoid wasp. There are tens of thousands of species of these, found world-wide. All are parasites, mostly parasitoids (parasites which eventually kill their hosts) preying on larvae of beetles, flies, moths, butterflies, etc., each wasp specializing in one or a few host species. I couldn't find which one would be the victim of this red-legged wasp.

The female wasp finds a caterpillar or maybe a pupa of the target insect, and lays an egg on or even inside it, using the long ovipositor at the end of her abdomen. This egg-laying tool is specialized to reach the specific prey; in some wasps, because the larvae it seeks are deep inside tree bark, the ovipositor is as long as the wasp herself.

The egg hatches, and the wasp larvae begin to eat their host, still alive.
"The tiny larvae that hatch fed upon the fatty tissues of the Caterpillar's body without damaging any vital organs. When the Ichneumon larvae are almost full-grown they begin to feed on the more vital organs, resulting in death of the caterpillar."
From Organic Garden Info
The wasp larvae then pupate inside the body of their prey, emerging finally as adults.

A gruesome story, especially if you have a vivid imagination, if you can feel empathy even towards the little white maggots and squirmy caterpillars. Not hard, since in reality, they are our distant cousins; they have their tiny delights and agonies, like us, if on a lesser scale. It's a dog-eat-dog world, difficult to understand.
I cannot persuade myself that a beneficent and omnipotent God would have designedly created the Ichneumonidae with the express intention of their feeding within the living bodies of Caterpillars, or that a cat should play with mice. - Darwin, 1860, letter to Asa Gray.
And yet, we are part of that tooth and claw economy, and we can find a benefit even in these wasps; they kill insects that otherwise would damage our crops and reduce our food supply.
Parasitic Wasps are arguably the most important beneficial garden insects. They’re critical because they operate at low population densities. That is, they’re the first check on insect pests. From Grow it Organically.
My little red-legged visitor flew away, eventually. I let her go; she's a solitary, so she should feel at home in my garden. Maybe she'll lay eggs in the aphids, maybe in some other animal that I really don't want in my plants. Or maybe not; maybe she'll just tootle around until the cold weather arrives, providing a spark of warm red on the cool greens of my shady haven.


  1. This was a fun post. Thank you.

  2. I was remarking to Wayne the other day that there haven't been as many wasps around the cabin this year. We didn't get a hornet's nest, but maybe that was a good thing. But the wasps that usually bother us during dinner at the picnic table didn't even show up. Must have been another reaction to the weird summer weather. - Margy

  3. I think the wasps that are missing from Powell's neck of the woods have come over to settle in ours! I've never seen so many wasps, hornets, and yellowjackets as I have this year.

    I don't think I've ever looked at one so close up, though. I kind of like those weird red legs!

  4. Can it bite pets such as cat, dogs or even humans?

  5. Probably not. It's very small, and that long thing at the back is for laying eggs, not for stinging.


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