In Minnesota, there are fourteen described species within the genus Hylaeus including one introduced non-native species, Hylaeus leptocephalus. Bees in this genus construct solitary nests in pithy plant stems and cavities in wood. Some species can produce more than one generation per year (bivoltine). Hylaeus are linear black bees with white or yellow markings on the face and legs. One species, Hylaeus nelumbonis, has red markings on its black abdomen. Another, Hylaeus basilis female, is almost entirely black, lacking any prominent white or yellow markings other than subtle markings on the abdomen. Males have prominent markings encompassing most of their face and females have two equal-sized patches. Hylaeus look like small mason wasps; they are almost hairless and females lack pollen-collecting hairs on their hind legs.

Females ingest then store pollen and nectar in their crop to transport the provisions internally back to their nest, where they are regurgitated into a prepared brood cell. Each nest cell is waterproofed with a combination of their saliva and secretions from their Dufour's gland (a gland in their abdomen). The mixture dries and produces a cellophane-like lining that holds the liquid provisions in the cell and provides a barrier for water and fungal/bacterial penetration. Hyaelus have a short bilobed or forked glossa (tongue) that they use to distribute the waterproofing liquid in their nest cells. Bees in this genus have two forewing submarginal cells, are very tiny, and range in length from 2 to 12 mm (0.07 to 0.47 inches).