Subject: Never saw this one
Location: Pennsylvania
May 31, 2016 5:10 pm
Hey bugman,
My son happened to find this interesting looking flying bug. It was buzzing along the grass. Not sure if it was injured. Any idea?
Signature: Sincerely, Mike from Philly


Female Stump Stabber, missing her ovipositor

Dear Mike from Philly,
We can tell you that this is a parasitic Ichneumon Wasp, but we are having trouble conclusively identifying it to the species level, so we have contacted Eric Eaton and explained out doubts.  The yellow antennae and shape of the abdomen rule out a male
Megarhyssa atrata which is pictured on BugGuide and Beetles in the Bush, and all the examples of  Therion morio on BugGuide have black heads.  What this Ichneumon looks most like to us is a female Stump Stabber, Megarhyssa atrata, but with a missing ovipositor, a condition we could not really explain.  See this BugGuide image for comparison.  We will get back to you when we hear from Eric Eaton.


Maimed Female Stump Stabber

Definitely agree with you that it closely resembles the female stump stabbed after doing a little more research on the Internet.  But why no ovipositor? Can it become disconnected when/after laying its eggs? Could a bird have eaten just that part of it? Hopefully Mr.  Eaton has an idea.
Thank you so much for responding to me.  Can’t wait to tell my son.  Keep me posted.

Eric Eaton Confirms our suspicions
This is a *female* M. atrata that has lost her ovipositor.  Sometimes they get “stuck” while in operation, and/or the wasp needed to flee a potential predator.  I have frequently found ovipositors lodged in logs or stumps, the wasp having been consumed by a predator while in the act of laying eggs.

Thanks for the confirmation Eric.
I have heard that sometimes the females get stuck while ovipositing and cannot withdraw, dying in the act.  Is that also true?

Location: PHiladelphia, Pennsylvania

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