Osmia uncicornis species group

The species of the O. uncicornis species group differ from those of the O. difficilis species group in both sexes by the foxy red tergal pilosity (whitish or yellowish in O. argyropyga), in the female sex by the lack of clubbed bristles on the fore tarsus and in the male sex by the following strongly derived characters: antennal flagellum distinctly crenulate, ventral side of middle femur with median keel-like projection, middle tibia swollen and curved, tergum 6 four-toothed and mediobasally with polished longitudinal keel or bulge (Fig. 5, 6), tergum 7 with narrow median projection possessing a straight to emarginate apical margin, sternum 4 medioapically densely covered with hooked bristles and prolonged into a triangular projection, sternum 5 with deep median incision, sternum 6 apically beset with curved bristles and apex of gonoforceps bifid.