Wikipedia
Eucerini
The Eucerini (often called long-horned bees) is the most diverse tribe in the family Apidae, with over 32 genera worldwide that were previously classified as members of the family Anthophoridae. All species are solitary, though many nest in large aggregations, and it is also occasionally possible to find large "sleeping" aggregations of males. Most, but not all, genera are distinctive in the unusually long male antennae from which the tribe derives its name (eucer- means true horned). They are most diverse in the Western Hemisphere.