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Photo#722449
Cute little posing Wasp - Arachnophaga - female

Cute little posing Wasp - Arachnophaga - Female
Basking Ridge, Somerset County, New Jersey, USA
September 1, 2012

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Cute little posing Wasp - Arachnophaga - female Cute little posing Wasp - Arachnophaga - female

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This is indeed a female Arach
This is indeed a female Arachnophaga (Eupelmidae: Eupelminae) and a couple of fascinating images. The one with the female standing on its legs is the typical "live" posture, whereas the other image is the contorted "jumping" posture that female eupelmines often die in. Females are great jumpers and prefer to jump than fly, which is why you saw it crawling around. I would not be surprised if it actually jumped from the edge rather than flew, though they often use their wings to extend the jump. They jump using their middle legs, but do not use leg muscles to power the jump. Rather, longitudinal thoracic muscles are used and the longitudinal force of action is changed into a vertical force acting on the middle legs in a sort of a Rube Goldberg contraption that results in the thoracic contortion you photographed. This is actually the first image I have ever seen of a female in the contorted jumping position that is live. I tried photographing a female Eupelmus jumping many years ago at 400 frames per second, but it was too quick to be captured at that speed. The only thing I can think of is that when you dumped it from the container it jumped and remained in the position long enough for you to take a picture before it stood up again.

If you compare the two images you can see in the standing female the thorax is comparatively low convex, whereas it is more acutely angled (arched) in the other. As a result of the thorax arching along the junction between the mesoscutum and scutellum, the mesonotum is shortened whereas the mesosternum remains the same length. Arching the mesonotum pulls the pronotum and head up over the anterior margin of the mesosternum, which results in the head being angled up. Arching also pushes down on the propodeum and base of the abdomen, which forces the apex of the abdomen up so that the body takes a more-or-less W-shape, which is clearly visible in your contorted image. Although not clearly visible from your image, the middle legs, which are directed straight posteriorly in the contorted image, have the tibiae and tarsi of the two legs crossed over each other so that the tibia and tarsus of the left leg are pointing out of the image whereas those of the right leg are pointed into the picture. I would greatly appreciate it if you could email me the images you took (hopefully at a large file size) at Gary.Gibson@agr.gc.ca. Superb images!

 
Thanks!
I'm not sure why, but for some reason I decided not to mention the fact that the wasp seemed to teleport instead of fly. That's how I caught it, I my container over it and then it teleported onto the side of the container then teleported to the other side of the container. I'll send you the pictures! (Also, maybe it was playing dead? I don't remember exactly, but I think it might have landed on it's side and I blew it onto it's stomach. Maybe. But it was so long ago I don't remember exactly.)

 
I really like the description
I really like the description of "teleported" as that aptly describes the rapidity of a jump! I also forgot to mention that our firewall prevents any email over 10MB so hopefully the images are not too huge.

 
Hi again!
I sent you links to the three full-sized images, and recently I found (well actually reared) another species of wasp that jumps! http://bugguide.net/node/view/726585

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