The infinita species-group

Based on a single species, B. infinita Casey, from the southwestern United States and northeastern Mexico. This species is distinctive in that the male lacks modifications of the antennae and the abdominal tergites, and is the only species with a ventrite modified (ventrite III). It also is unusual in having a very broad multidentate spine in the internal sac; a feature that is shared with the otherwise very different species B. corniventris, which has elaborate modifications of male tergites 1–2, and lacks any modifications of the ventrites.