Large, Brown, Crane-fly-like Ichneumon Wasps

2011 December 3

Rather large but very spindly orange-brown insects, like this one, are regularly drawn to our porch light in the summer. They look superficially like crane flies, but they aren’t.

It is an Ichneumon wasp, in the subfamily Ophioninae, and it’s either one of the ones in the genus Enicospilus, or a Short-Tailed Ichneumon in the genus Ophion.

I’m not sure whether it’s a male or a female. For most ichneumons, it is easy to tell the sexes apart because the females have long, obvious ovipositors. The short-tailed ichneumons, though, have a short ovipositor and so the difference isn’t so pronounced.

These particular ones are very common, probably because they are generalist parasitoids who lay their eggs on a variety of caterpillars. Since they mug caterpillars directly, they can lay eggs on them without the need of a long ovipositor. And since they are quite large, they only lay one egg per caterpillar.

The majority of ichneumons are harmless to humans, because their ovipositors are specialized for things like boring into wood, or snaking down tunnels, or any of a variety of weird contortions to enable them to get eggs onto their hosts. However, human flesh is pretty similar to the caterpillar flesh that the short-tailed ichneumons are evolved to penetrate, and so they can actually “sting” (although I gather that no actual venom is involved). Any egg that they might inject into you will be quickly killed by your immune system, though (since your immune system is very different from that of a caterpillar). So it might be a little painful, but at least you won’t have a big, gangly wasp crawling out from under your skin a few months later.

6 Responses leave one →
  1. December 4, 2011

    Looking at their bodies, I started wondering about the fluid dynamics of their flight. The bulkier back end might have some effect on maintaining a laminar flow of air around their frame. I don’t think I found out if that was true or not, but I did find this. Additionally, there are fluid dynamics animation videos on youtube looking at insect flight, but I have to admit, I can’t make heads or tails of them.

    Awesome photos and post as always.

  2. December 4, 2011

    The top photo almost looks like one of Tiffany’s dragonfly pins. If you can just get over the ick factor of many insects (which you apparently have accomplished!), there’s beauty there for the asking. Thanks again for your close-ups of things most of us pass by without a thought, or at least, without a positive thought…)

  3. December 5, 2011

    KT: The aerodynamics would be part of it, but one of the things that confuses the issue in evolutionary situations is that they aren’t doing just one thing. It needs to be shaped to fly, but it also needs to carry a large cargo of eggs, which have to be injected quickly into a caterpillar that may have long defensive bristles, will probably thrash wildly, and in some cases might have defensive chemical sprays. The long abdomen gives a good standoff distance; the bulbousness at the end allows the eggs to be stored near the tip so they don’t have far to travel and so can be laid quickly; the thinness side-to-side would allow the abdomen to slide in between defensive bristles; and all of these have to be shaped so that the insect can still fly quickly through the air with good maneuverability both to avoid predators and to attack prey.

  4. December 5, 2011

    Thanks, Anne. This is one of the cases where I didn’t realize just how attractive of an insect it was going to be until well after taking the pictures. A line of jewelry based on some of the spiffier specimens here would be pretty cool. Hmm. I wonder how hard it would be to do. The trick would be making them accurate enough to look nice, while still having them be inexpensive enough that people could afford to buy them.

    Speaking of insect replicas, here’s a bunch by a company that makes them for movie props:

    http://www.filmflies.com/

  5. Geoff Davies permalink
    August 14, 2013

    Have you any video footage of this beastie? This Ichy wasp is very similar to a beastie I saw flying fairy-like along my ivy covered fence in Portishead on the w/e. My beastie appeared a dark red compared to the orangy colour of this one. Now I know there are 30,000 of these beastie types but it would be nice to know exactly what it was. Please can you help?

  6. August 14, 2013

    Geoff: No, but your description of the flight of the one you saw, sounds pretty close to the way that these flew.

    There is a pretty good chance that yours is also in the Ophion genus, they range from pale yellow to dark red. Like this one:

    http://bugguide.net/node/view/158491/bgpage

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