Palaearctic Osmia bees of the subgenera Hemiosmia, Tergosmia and Erythrosmia (Megachilidae, Osmiini): biology, taxonomy and key to species Author Müller, Andreas text Zootaxa 2020 2020-05-14 4778 2 201 236 journal article 22161 10.11646/zootaxa.4778.2.1 2bdbfd60-8edf-4efc-9fc3-34649a0e3896 1175-5326 3826170 61BA688B-E383-4A4C-A9F6-D4F53E55645A 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.