Hi, I am in Carlisle which is a stone's throw from Concord in same county - I have also been enjoying watching these giant wasps over the last week. I found the black ones (assume M. atrata) sharing the same log with the yellow and brown ones. Are they M. macrurus or something else?

I just was out on my porch haveing a smoke the other day and almost had a heart attack when I say this gigantic wasp sitting on the edge of my college dorm's cigarette bucket. I went right upstairs to look it up. I didn't even know we had bugs that big in New England, but then again I'm originally from main where all the big bugs freeze to death before you get to see them or there are too many woodland acres for them to hide in.

Ah, Maine. More nature, less people to push them into plain site. LOL.

because I forgot to mention that there were actually two of these wasps ovipositing in the same tree just like your M. macrurus. Do these sting I wonder? Or are they like Sphecius speciosus (Cicada killers) they only look viscious but don't sting?

Megarhyssa identified here at BugGuide. We've always assumed that meant there were more than one species that couldn't be identified from photos, but have not seen the list of possibilities. We seem to remember Eric discussing that these giant ichneumons don't have stingers, just these long ovipositors. Cicada Killers, on the other hand, we assume have a powerful sting to take down a cicada. We have assumed that they choose not to sting if you're not bothering them but could deliver a nasty sting if they felt threatened. It will be interesting to see the responses you get on this question. There's always more to learn!

While the females do have stingers, I seriously feel that they are reluctant to sting anything other than a cicada. Last year I studied a colony in a Massachusetts Cemetery,I've wrestled cicadas away from females (I collected 10 cicada specimens in this manner) and never got stung.

Do I think they'll sting me if I crush one with my hand? Probably. If I accidentally sit on one?, Probably that too. If you are allergic to bee stings, then it's probably better to not take the chance.

What concerns me is that people see nothing but a big giant buzzing wasp and automatically assume they are hostile and make every attempt to kill them which really isn't necessary.