Osmia aquilonaria Rightmyer, Griswold, & Arduser, 2010  

Males of O. aquilonaria are most similar to the palearctic species O. svenssoni and O. steinmanni, but can be differentiated from them by the shape and pilosity of S4 and gonoforceps. Osmia aquilonaria males can be distinguished from all other members of the inermis species group (except O. svenssoni and O. steinmanni) by the special form of the hairs on S4 (i.e., with two patches of hooked bristles both along apical margin and on premarginal area, along apical margin the bristles oriented horizontally and on premarginal area directed increasingly vertically. Females of O. aquilonaria can be distinguished from the only other nearctic member of the inermis species group, O. laticeps, by the more pointed third tooth and the parallel condylar and outer ridges of the mandible (O. laticeps with third tooth forming cutting edge extending from fourth tooth, and with apically converging condylar and outer ridges). Females of O. aquilonaria are extremely similar to those of the palearctic O. svenssoni, and are not readily differentiated from them other than by their respective geographic distributions.