Females are blood-sucking pests of many warm-blooded animals, including people. Males do not feed on blood. Found worldwide, they cause great annoyance, and are suspected vectors of several livestock diseases, including hog cholera virus, infectious anemia in horses, and anaplasmosis bacteria of cattle. Larvae are predaceous on small invertebrates and consume organic matter.
Adults are moderate to large flies (14 to 19 mm long) with a "swept-wing" appearance and large heads that are mostly compound eyes. Mature larvae are white, brownish or greenish in color, spindle-shaped, and taper to a point at both ends. The head is small, cylindrical and retractable.