Boreantrops albipes, Kits, Joel H. & Marshall, Stephen A., 2015

Kits, Joel H. & Marshall, Stephen A., 2015, A revision of Boreantrops Kits & Marshall (Diptera: Sphaeroceridae: Archiborborinae), Zootaxa 3915 (3), pp. 301-355 : 310

Boreantrops mexicanus group

This group of 19 species is characterized by a sculptured mesoscutum, with fine lateral ridges at the bases of most setae creating a pitted appearance, and tab-like structures extending ventrally from the hypandrial arms in males. Within the group, two subgroups seem apparent. Five species ( B. albipes sp. nov., B. avignis sp. nov., B. costaricensis sp. nov., B. masneri sp. nov., and B. peruvianus sp. nov.) form one subgroup (the avignis subgroup). The species of this subgroup share a subtriangular scutellum, with the ratio of the length of the scutellum to the distance between the apical bristles at least 3:1 and usually a distinct concavity on the dorsal surface, clear wings, and usually abdominal tergites with only small areas strongly sclerotized. This subgroup appears to be absent from the higher elevations occupied by other Boreantrops, and includes the only species known from lowland Amazonia ( B. peruvianus ). All species in this group are identifiable based on external characters. The two Brazilian species in the genus, B. friburguensis sp. nov. and B. hispidus sp. nov., may belong to this subgroup as well; both are easily recognized by the presence of additional fine setae on the disc of the scutellum and extensive orange around the leg joints.

Eleven of the 12 remaining species are treated here as the mexicanus subgroup, characterized by a normallyshaped scutellum, with the ratio of the length of the scutellum to the distance between the apical bristles less than 2:1 and dorsal surface flat to convex, brown wings with white spots on crossveins and vein R4+5, and usually most of the abdominal tergites strongly sclerotized. Species in this subgroup are only known from Mexico and Central America. They may represent a relatively recent radiation, as all species are fairly similar and most are only separable based on small differences in the male genitalia. As species in this subgroup have largely overlapping ranges and differ in few external characters, accurately associating females with males is difficult. Length of the spermathecae may represent a useful character for separation of females, but this is difficult to test without having large series of accurately associated females available to test the variation in this character. DNA sequences may prove to be a useful character set in resolving the remaining issues in this group.

The only brachypterous species in the genus, B. apterus sp. nov., appears to belong to this group based on the presence of the tab-like structures on the hypandrium, although the mesoscutum is smooth. It does not show obvious affinities to either of the subgroups.