Family: Asilidae, Robber Flies view all from this family

Description 1/2-3/4" (13-19 mm). Humpbacked. Head and thorax sandy to dark brown, with white or yellow beardlike bristles. Male's abdomen steel-gray with last segments silvery; female's lighter gray with 2 black spots in middle. Legs spiny silvery gray with orange and black tibiae. Wings clear to smoky.

Food Adult feeds on other flies, especially deer flies and horse flies, as well as flying ants, small bees, true bugs, grasshoppers, butterflies, and moths. Larva preys on white beetle larvae and other insects in soil.

Life Cycle Eggs are laid on soil, into which larvae burrow in search of prey. They overwinter underground and pupate in spring. Adults fly August-September.

Habitat Pastures and open fields.

Range S. United States east of the Rocky Mountains.

Discussion The Bearded Robber Fly often overtakes horse flies or deer flies in flight, whirring at high speed. It captures them and sucks them dry while standing on a leaf or twig. The largest robber fly encountered in North America is usually the California Bearded Robber Fly (E. californicus), 3/4-7/8" (19-22 mm), which is black with white pile. This species was formerly assigned to genus Erax.