Monday, September 16, 2013

An interesting little wasp

Last Saturday, I found myself strolling down the long linear Milford Center Prairie corridor - an abandoned railroad right-of-way - when an eagle-eyed member of my party spotted this gorgeous little case, hanging from a pendant thread. It resembled an Easter egg painted in black and white, albeit on a tiny scale. The case was only a few millimeters in length, and dangled from the branch of a Sandbar Willow, Salix interior.

I really had no idea what made it, but thought it might be a wasp, as some of them make similar cocoons. But my efforts to come up with an identification bore no fruit, so I turned to the amazing BugGuide megasite. Within minutes of posting this photo, I had my answer. Someone quickly identified the family of wasps, and from there it was easy to come to a specific ID: Charops annulipes (no common name).

The object in the photo is indeed this wasp's cocoon, and it hangs it from a thread for a reason, as we shall see.

Researching this issue reminded me of a photo that I took in mid-August of last year, in another prairie remnant not far from where we found the cocoon. I dug back into the files, and quickly found this photo, which I had just labeled as "wasp". This animal was tiny, almost gnatlike in appearance, and I only managed two so-so shots before it darted off, never to be seen again. Well, I compared it to the relatively few decent photos that I could find of Charops annulipes, and this seems to be it!

Like so many of the micro-wasps, Charops is a stunner. I remember the encounter very well, and how I wished I had had a bit more time to compose better images. More than a few times I've spotted tiny parasitoid wasps hunting the foliage, and have been dazzled when I finally lock them into the sights of my macro lens. With the naked eye, they are nothing - inconsequential mosquito-sized bugs that would easily be passed by. The magic of magnification reveals amazing detail of structure and color. But then comes the problem of identification. The wasp world is utterly massive, and there are no comprehensive Peterson field guides to help. I have many mystery photos labeled as just "wasp", as this one was.

Charops is a parasitoid, and lays its eggs on the caterpillars of moth species such as this snout (I believe it is the very variable Green Cloverworm, Hypena scabra). The wasp probably preys on other Noctuid moths as well. It's the same old grisly story - wasp larvae burrow into the host caterpillar, and eat it alive.

But turnabout is fair play, and apparently Charops can fall victim to its own set of parasitoid predators. Hence, the cocoon suspended in space by a thread. Dangling in midair makes it harder for would-be predators to find and reach the wasp cocoon, thus upping Charops' chances of survival. Or at least that's how I understand this elfin wasp's lifecycle.

1 comment:

OpposableChums said...

Amazing. Thanks for the post.