Ichneumon from Grocery Store

2016 November 16

On November 3, 2016, Sandy spotted this wasp on the window of our local grocery store. All she had to take its picture with was a cellphone, but she got a couple of pretty good pictures regardless:


This is really late in the season for us to be seeing any type of insect. This particular one looks like a wasp in the subfamily Ichneumoninae, which includes a number of species of black wasps with white markings in the middle of their antennae.


I’ve muttered about this before, but boy, are the various ichneumons hard to identify. There are about 700 known species in this subfamily alone, but good luck identifying them because their differences are mostly in the hosts that they parasitize, which is not something you can tell by looking at an isolated specimen in a picture. This particular subfamily has a short ovipositor, and mainly lays eggs on various hairless caterpillars – probably mostly cutworms.

4 Responses
  1. November 16, 2016

    Can they use different hosts in a pinch?

  2. November 16, 2016

    Yes, there is a certain amount of host-switching, although it depends on the wasp. Some are relatively broad-minded about the whole thing, while others are startlingly specific. I think the generalists have access to a lot more hosts, but a lower success rate because they aren’t so exquisitely adapted to overcome the specifics of the host’s physical defenses and immune system. The highly-specific ones have a very high success rate, but only if they hit the right host. If they can’t find one, they evidently will just go for something reasonably close, but the success rate plummets.

    Speaking of specificity, the Wikipedia page about ichneumon wasps mentions a fairly extreme case, where the wasp is a parasite of a paricular species of butterfly, and this butterfly is in turn a nest parasite of a particular genus of ants. So the wasps have to run through the ant nest and avoid getting killed by the ants before they can get to the butterfly caterpillars that they want to lay their eggs on. This is not the sort of situation where I’d expect them to get a lot of competition from other wasps, but once they are adapted to look for their hosts in this particular place I don’t think they have much ability to just decide, “the heck with this, I’m just going to lay my eggs in that cutworm over there.”

  3. Carole permalink
    November 16, 2016

    One of the good guys.

  4. November 22, 2016

    Good Lord. Running through the ants sounds like trying to make a living scavenging things that fall off cars on the freeway.

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