There are more than 2,000 living species of sweat bee (Family Halictidae) worldwide. They are so named because they are attracted to the sweat of humans. Fortunately, they seldom sting and when they do the sting is minor.
There are four species of Augochlora in the United States, only one of which is found in Minnesota. Pure green augochlora (Augochlora pura) is a moderately-sized, solitary, metallic green sweat bee. It is very common in the eastern half of North America west to Minnesota. It is found from April to October in woodlands and nearby thickets and pastures.
The overwintered mated female emerges in April. Using an existing insect burrow in dead wood as a starting point, she digs a nest consisting of many branched burrows. She places a pollen ball and nectar in each burrow then lays a single egg on the pollen ball. The first generation offspring emerge as adults in June. By the end of June they have constructed their own nests. The larvae or pupa of the last generation overwinter and emerge as adults the following spring. Adult females overwinter beneath rotting logs in a state of diapause. Males die in the fall.
Sweat bees are identified by a short tongue with a short, pointed last segment; single groove below the base of each antenna; lobe at the base of the hindwing longer than the submarginal cell; and basal vein on the wing strongly arched. Pure green augochlora is distinguished by the completely bright metallic green or coppery body; abdomen not conspicuously striped; dark brown, oval-shaped structure at the base of each wing; wing with three submarginal cells, the first longer than the third; marginal cell of the wing squared off at the end; and upper margin of the plate on the upper lip intruded upon by lobes of the plate above it.