Apicotergite = end of abdomen? I added a picture showing small hairs there.

appears to be in the subgenus Anoplius, since (from what I can see in this shot) it lacks a tarsal rake. The abdomen shot was pretty conclusive.

I added two pictures of the front, left leg. There are a few spines.

To me, it doesn't appear to have a "true" tarsal rake, which excludes all other subgenera except Anoplius. Because of the strength of the spines I would say it is something in the illinoensis species group, since most of the species in the nigerrimus species group have weakly spined front tarsi. In fact, it is probably illinoensis itself. Unfortunately closer examination is needed to separate it from ventralis. Both should be present in NY.

I have more pictures. None are significantly closer than the ones I have posted. Where are the differences between the species visible? How close do you have to be to see them?

Your pictures are great, don't get me wrong, but it's easy to misjudge some characteristics from field photos. It is far more accurate to identify a specimen in-hand under a scope. Two of the best characteristics for separating illinoensis from ventralis is the general hairiness of the thorax and the length of the basitarsal spines. In ventralis the propodeum and mesopleuron are provided with a number of distinct, erect hairs. Erect hairs are virtually absent in illinoensis. The basitarsal spines of illinoensis are much longer than in ventralis, the upper row more than 1.5X the width of the basitarsus and the lower row as long as or slightly longer than the width of the basitarsus. In ventralis I have seen the spines of the lower row are considerably shorter than the width of the basitarsus, some not much more than half that width.

Of this wasp.