Identification
According to
Insects of Cedar Creek: Adults have bare humeri (postpronotal lobes), though these are often hidden by the concave posterior of their close fitting heads.
Food
The larvae are primarily aphid predators. Some are generalists, other specialize in just a few species of aphids. Those in the Pipizini tribe specialize on gall forming aphids.
Adults exploit pollen and nectar produced by native plants having large inflorescences and flat corollae (e.g. Apiaceae, Asteraceae, Ranunculaceae and Rosaceae).
Remarks
They are considered efficient biocontrol agents. They are also minor pollinators.
The classification of tribes within this family is in flux. Only Paragini and Toxomerini seem to be monopyletic.
Internet References
University of California, Davis. Biological Controls for aphids.
