I've collected many and am trying to find a key. Any suggestions?

Townes was the last one to do a key as far as I know, and that was many decades ago! I have a copy, and I'll amend this message with the pertinent info at some point. Might even be willing to copy the section on Pepsis and Hemipepsis for you. The genera are in need of revision, especially since I'm sure there are newly-discovered tropical species.

I've since got a hold of P. Hurd's Nearctic Pepsis Key and identified this female as P. formosa.
Cheers,
Todd

I've been moving things around and I saw this pair of photos. This is without a doubt Pepsis and not Hemipepsis. As long as it was keyed out there should be no problem moving this to a species guide page. Separation of P. grossa (=formosa) is pretty straightforward, for a spider wasp, at least. It also roughly matches the specimens I have seen.

How is Pepsis grossa distinguished from other Pepsis species? There's no information on the species page, and the genus page says only "Large blue-black wasps, most with orange wings. Some species have orange antennae."

I went ahead and added some text. I'll add illustrations later, but they'll probably have to be line drawings since I have no photographic equipment good enough to show those characters. I'm probably not going to add info to the species pages until I get all the genus pages finished (unless, of course, the genus is monotypic).

I've been very slowly but steadily adding information to the Pompilid guide pages. It has been slowed a bit more because of the field season is nearing its peak here. Also, I live in Ohio and have not had the need to accumulate technical literature on Pepsis, so I would have to do it in a relatively short time to put together a really good guide page. For the mean time I can put a text only description on the pages until I can get together something better. It'll probably be over the next few days.

I've looked for the Townes key with no luck so far.
Would you be able to copy the Pepsis Hemipepsis section for me?

townes key for hemipepsis is pretty useless, it doesn't give good descriptions, and species like hemipepsis tousaintii are almost exactly like a species of entypus. I'll make a copy for you but I guarantee you'll be very confused by the end of the hemipepsis section.