Well, I have the very sneaking suspicion that this is a male M. atrata--it was very closely associated with the female I saw at the same time, and to me, it looks quite close to the image on this page showing a male M. atrata. I believe Eric made the statements below just assuming that male M. atrata was as dark as the female. (No disrespect meant to Eric--we all assume things--we'd never get anywhere on ID's if we did not!)
What do you all think?
My conclusion, tentatively, had been that the male did not seem to be identifiable as to species by a photograph--I had made the identification above based on the association with a female.

but interestingly, our understanding is that Megarhyssa are very special in that they all prey on the same species and it could be in the same tree at the same time. The difference is in the length of the ovipositor, so they feed at different depths in the tree. Apparently when the females are about to emerge, males of greenei, atrata and macrurus all show up at the tree and wait!

Well, my recollection of these two (the only Megarhyssa I've ever seen) is that the male was right close to the female--I thought it looked like mate guarding. That, however, is a pretty old recollection!

I'm wondering about the ID of males here--the one photo I've found of male atrata looks real similar to what we are calling male macrurus. Perhaps the males can't be told apart? I don't know--just speculation. Does anyone have any authoritative information?

M. macrurus is listed pretty commonly at North Carolina State collection for this state, as is atrata.

Awesome. Thanks for catching my errors. I will update the photo captions, at least, and then, perhaps, add some guides for the indivdiual species later.

At least I had the genus correct!

Again, thanks for your help.

Patrick Coin
Durham, North Carolina