Eventually, however, Dr. Buck will drop by and educate us both.

I measured the flowers, and confirmed my impression that this thing was tiny--probably less than 10 mm body length. That does not seem to fit the size (forewing length 8-12 mm or so) for, say, Euodynerus megaera, given in Identification Atlas of the Vespidae of the northeastern Nearctic region. But the wings, right, very dark, like the two Euodynerus species you mentioned!
So I am wondering if this could be something like a Microdynerus, which I am guessing, are noted for being small. We have examples in the guide here only from the West, but the guide page mentions that genus is holarctic, with 40 species. So I am moving the images up to subfamily level.