Osmia difficilis species group

The species of the O. difficilis species group differ from those of the O. uncicornis species group in both sexes by the whitish tergal pilosity, in the female sex by the clubbed hairs on the fore tarsus and in the male sex by the normal shape of antennal flagellum, midleg and sterna, the trifid tergum 6 with strong median projection (Fig. 7), the evenly rounded apical margin of tergum 7, the lack of hooked or curved bristles on sterna 4 and 6 and the spatulate apex of the gonoforceps.