A review of the (Hymenoptera, Halictidae) and keys to the shiny green Halictinae of the midwestern United States.

and other shiny green Halictinae have had various taxonomic issues and are often misidentified. One prevailing taxonomic issue is that (Fabricius) has two subspecies, that have long been recognized as morphologically distinct ( and (Smith), but the subspecies are inconsistently applied in the literature. Here, we review the of the Midwest and further address the species in the broader United States to resolve the outstanding taxonomic issues with the midwestern species. We provide identification keys and diagnoses for the genera and species of the shiny green Halictinae of the midwestern United States, which includes the genera , , , and . This work results in taxonomic changes to . (Smith) is split into two species, with the name retained for the eastern form, and (Patton), , reinstated for the western form. is split into five species, with two of those species occurring in the midwestern United States: and (Smith), Examination of the holotype of (Smith) revealed that it does not agree with the prevailing concept of ; it is reinstated as , , but is currently known only from the holotype female from Florida. (Smith), long considered to be a synonym of , is also distinct, and we are reinstating , , though the range of this species is unclear. We further recognize (Friese), , from South and Central America, as distinct. These changes result in a total of three species in the Midwest and seven named species in the United States. We are aware of additional species from the southern and southwestern United States that are undescribed, and we highlight additional taxonomic work that remains to be done.