Would it be anyone from Utah State? As far as Pompilids go that's "where it's at". Dr. Pitts is working on genetic characters to work out a phylogeny the Pompilidae (among other projects). I wish I lived in Utah so I could go to grad school there!

It was Dr. Pitt himself who made the identification.

That's nice...there aren't very many entomologists that would give you a more sure ID on a pompilid than him.

I wouldn't have missed this series of pics when it was first posted...really nice! I also wish there was a simple identification coming your way, as well. In the U.S. the genus Poecilopompilus is fairly easy to pick out from anything else. Unfortunately the three species (counting P. flavopictus of extreme southern Texas) are NOT quite as easily distinguished from each other. This is due mostly to the widespread and extremely variable P. interruptus. Evans commented in the monograph of the pompilini that interruptus "...almost defies description", especially in terms of coloration. What I'm getting at is that coloration is the least reliable character for separation. Size is also not very reliable, either, since it is variable on the basis of the size of the spider that was provisioned (the biggest spiders=big female spider wasps), but in general P. algidus is larger. The best way to identify any spider wasp is structure. In these species it is the type of claws on the anterior tarsi, the number of tarsal comb spines (this is obviously a female, so we'll disregard male ID for now...males won't have comb-spines on the anterior tarsus because they don't dig nests), and the convergence of the eyes. The eyes of P. algidus are very convergent at the top of the head and they have three strong tarsal comb-spines. Also, the claws of the front tarsi are bifid (essentially two long teeth, side by side). In P. interruptus the eyes are not as convergent, they have four rather weak comb-spines, and all of the claws of the tarsi are dentate (a small erect tooth on the inner side). I don't think enough of this is visible in the photos, so POSITIVE ID is next to impossible. But if I had to make an educated guess I would say this is P. algidus coquilletti, based on Evans' 1950 description.

I know there are at least two color forms for P. interruptus, though, so I'd wait for Nick Fensler or another pompilid authority to make a final determination. Great series of images!