The ‘ red-tailed’ Lasioglossum (Dialictus) (Hymenoptera: Halictidae) of the western Nearctic Author Gardner, Joel AA15FE6E-921A-46D6-BC67-88E067F283D9 Department of Entomology, University of Manitoba, 12 Dafoe Rd., Winnipeg, Manitoba, R 3 T 2 N 2, Canada. clickbeetle3364@gmail.com Author Gibbs, Jason BA42A49F-3EBC-4679-8F03-A58E798106B1 Department of Entomology, University of Manitoba, 12 Dafoe Rd., Winnipeg, Manitoba, R 3 T 2 N 2, Canada. jason.gibbs@umanitoba.ca text European Journal of Taxonomy 2020 2020-11-27 725 1 242 journal article 9466 10.5852/ejt.2020.725.1167 9e062836-3946-4ac6-8910-304cadff0d4b 4298139 89FA8DDF-F4B9-417A-A5AF-B2BC9660E024 The Lasioglossum clematisellum species complex Species included Lasioglossum clastipedion sp. nov. , L . clavicorne sp. nov. , L . clematisellum , L . julipile sp. nov. , and L . perditum sp. nov. Diagnosis The Lasioglossum clematisellum species complex comprises several morphologically and genetically similar species found in deserts of the southwestern United States and northern Mexico . Females can be fairly easily diagnosed by the combination of wings pale with extremely short, inconspicuous white hairs, metapostnotal rugae strong and usually reaching the posterior margin, punctures of the face, hypoepimeron, and mesepisternum all distinctly separated, and T2 without dark spiracular spots. Males are small (< 5 mm ), with the metasoma relatively narrow and all black to brown, rims of T1–3 largely impunctate, flagellomeres relatively long (F2–11 1.5–2 times as long as broad), head and mesosoma usually shiny with distinctly separated punctures, and metapostnotum usually with strong rugae reaching the posterior margin and extending onto the dorsolateral slope. In addition, males of this group often lack the second submarginal crossvein in one or both forewings, therefore possessing only two submarginal cells, and in one species ( L . perditum sp. nov. ) this is the usual condition. The male of L . clavicorne sp. nov. is unusual and lacks many of these diagnostic characters; L . clavicorne sp. nov. is included in this group mainly based on female morphology. These species are usually challenging to distinguish morphologically, but most are limited geographically and so collection locality may be used as an aid to identification. Lasioglossum clematisellum is the only species in this group with a very large distribution.