All five segments of the hind tarsus are similar in width. In every bee that I can think of, the first (proximal) segment is distinctly wider than the subsequent ones. If we could see it, wing venation would also be a great help, but I admit that I am probably also relying on the fact that it is unlike any bee species that I know of. The fact that the lateral lobes of the pronotum do not reach back to the tegulae and the absence of a petiolate gaster suggest it is in the Crabronidae (where arguably the bees belong) but I am not sufficiently familiar with genera like Pison, Tachysphex or any of the others to know just where it belongs.