Robber flies mate in early summer. A ritual involves aerial displays and abnormal buzzing sounds. Once a female robber fly has been fertilized, she will lay her eggs in the soil. Before winter, the eggs hatch and the larvae will squirm around beneath the surface, feeding on tiny soil-inhabiting insects and other insect larvae. Robber flies overwinter as larvae or pupate in the soil. The adult fly will emerge in late spring or early summer. Robber flies live about one year.
