Wikipedia
Pseudosphex is a genus of tiger moths in the Erebidae family. These moths are mimics of a variety of Hymenoptera. The prefix "pseudo" means "false," and Sphex is a type genus of wasps.
"In the cases of moths being like various species of the Hymenoptera aculeata [stinging wasps] it is impossible to argue that the same environment and general conditions can produce habits in moths which are of no use whatever to them except as a disguise. But if the moths themselves were not like the wasps one might argue that it was accidental that the habits were so alike, but the general appearance and structure are in conjunction with the habits so alike that in the species of Pseudosphex it is impossible to distinguish moth from wasp on the flower-heads of Ageratum conyzoides unless one is within eighteen inches or so, while on the wing at any distance it is quite impossible to distinguish them ...the species of Pseudosphex are mimics of the highest degree."