The heads of adults have a depression between the eyes when viewed from the front. They have long, strong legs for grabbing prey. Some robber flies resemble bees in a appearance but can readily be separated since true flies have only one pair of wings. Many have wings marked with darker patterns and they hold their wings outstretched. Larvae are parasitic on immature stages of other insects including Coleoptera, Diptera, Hymenoptera, Lepidoptera, Neuroptera and Orthoptera.
Adults lay eggs in the soil or in plants.
Eggs hatch into slender, shiny, white, legless larvae that develop through several stages before pupating. The life cycle usually requires more than one year to complete. Adult robber flies perch on stems of low plants or other objects and attack prey in the air. They feed on bees, beetles, dragonflies, other flies, grasshoppers, leafhoppers, wasps, and other insects. Larvae live in the soil, in wood and other habitats, feeding on organic matter, other arthropods such as white grubs, beetle pupae and grasshopper egg masses, and they may be carnivorous.