Dieunomia 
Large Sweat Bees

In Minnesota, there are two described species within the genus Dieunomia, and both are narrow oligoleges specializing on collecting Helianthus (sunflower) pollen. Dieunomia nest in the ground in sandy sites and often form small to large aggregations of nests. The nests are solitary and very deep (average 105 cm or 40 inches in depth). The species that occur in Minnesota produce one generation per year with the larvae overwintering in a prepupal stage. Males emerge the following summer a few days to a week prior to the females and patrol either the nest aggregation area or nearby Helianthus (sunflowers), searching for females.

Dieunomia are very large sweat bees and range in length from 8 to 19 mm (0.3 to 0.75 inches). Both males and females have a dark gray or black integument and long wings that are smoky or dark (D. heteropoda) or just with dark tips (D. triangulifera). D. triangulifera is very rare in Minnesota and was last collected in 1951. Dieunomia males have a flattened last antennal segment and protrusions on their mid- and hind leg tibia that are used during mating. Females collect pollen on the hind legs and hairs on the underside of the abdomen. Dieunomia can be confused with large Andrena species. However, Dieunomia lack facial foveae and have a V-shaped indentation on the base of their first abdominal segment (T1).​