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Chalcid Wasp - Zaischnopsis coenotea - female

Chalcid Wasp - Zaischnopsis coenotea - Female
Montrose, Laurens County, Georgia, USA
September 12, 2011
Size: 3-4 mm BL
Found literally running on leaves of several different trees on edge of forested area. I couldn't keep up with this one very well as she refused to stop. She also must have thought of me as "comfortable" as she jumped on and ran all over my hand, arm, and torso for a good while, never slowing down. I think this one may go in Zaischnopsis genus.

Images of this individual: tag all
Chalcid Wasp - Zaischnopsis coenotea - female Chalcid Wasp - Zaischnopsis coenotea - female

Moved from Eupelmidae.


This keys out to this genus. The species appears to be different than the one decribed by Dr. Gibson as Z. bouceki. This may be Z. coenotea in which females are described as having an ovipositor sheath that is banded and dark colored subapically. Both species have been found previously in Georgia. Dr.Gibson can make the species call on this one.

See reference here.

Yes, both a very nice image and identification! It is a Zaischnopsis coenotea female.

The remarks about it running around, even on one's hand, illustrates that female eupelmines prefer to walk (run) about than fly unless disturbed, at which time they escape by jumping. This is because females of this group (Eupelminae) have a modified skeletomusculature that increases jumping ability through the use of indirect rather than direct muscles acting on the middle legs for jumping. In other chalcids the muscles powering jumping are dorsoventral muscles, one on either side of the mesothorax attached dorsally to the thorax and ventrally to the middle leg of the respective side. When the muscles contract they rotate the middle legs such that a jump occurs. In female eupelmines the muscles powering jumping actually are even larger longitudinal pleural muscles on each side of the thorax, which give the characteristic, convex "cushion-like" sides of a eupelmid thorax. When these muscles contract the energy is initially stored in a small pad of resilin on either side of the thorax. Resilin is a rubber-like protein that is very efficient for storing and releasing energy with minimal loss (resilin is also used in fleas as part of their jumping mechanism). When the two pads of resilin pads contract they release the energy produced by the pleural muscle contractions in a single "burst" of energy that causes the dorsum of the thorax to explosively arch up in a tent-like manner, which pulls up on a slender tendon that is all that is left of the original dorsoventral "jumping" muscles of other chalcids. Because the tendons are attached to the middle legs like other chalcidis pulling up on them produces the same jumping action, but much more powerfully. However, the explosive contortion of the thorax necessary to pull up on the tendons could cause the dorsal thoracic sclerites to be ripped away from the mesopleuron if the axillary sclerites were not modified to prevent this. In other insects the axillary sclerites are small sclerites at the base of the wings that link the dorsal and pleural parts of the thorax to the wings to enable it to fly. In female eupelmines the sclerites are modified to prevent the thorax from ripping apart during a jump and thus likely do not work as well for flying, though this is just an assumption. However, it would explain why there is a "tendency" for brachyptery in female eupelmines. If flight ability has been compromised because of modifications to increase jumping ability there is less need for wings. Male eupelmines however retain the primitive body structure, which is why they look nothing like females and like other insects fly readily. Fascinating group of insects, no?

thank you ever so much for this thrilling explanation -- and to Jon for the excellent photos.

Fascinating? Absolutely!!
Thank you, Dr. Gibson, for the wonderful exposition. This is the sort of info generally inaccessible to short-attention spanners like me who would otherwise have to wade through dry text, only half-understanding what we read. Generally, behaviours or explanations of "why" an insect does what it does are hard to suss out and normally don't answer (unlike what you have noted above) why males and females look or act differently. As you say, the female I encountered was reluctant to take flight, preferring to jump from leaf to leaf until finally jumping onto my hand, behaviour that was mystifying since most wasps would simply zip off flying. Again, thanks!!

Moved from ID Request.