Asilidae

The Asilidae are the robber fly family, also called assassin flies. They are powerfully built, bristly flies with a short, stout proboscis enclosing the sharp, sucking hypopharynx. The name "robber flies" reflects their notoriously aggressive predatory habits; they feed mainly or exclusively on other insects and as a rule they wait in ambush and catch their prey in flight.

Overview

The Asilidae are a family in the order Diptera, the true flies. The common name for members of the family is the robber flies. The Asilidae are cosmopolitan, with over 7000 described species. Latreille was the authority for establishing the family in 1802. The Asilidae, together with Bombyliidae and Therevidae, are the most representative families of the superfamily of Asiloidea and they form one of the most characteristic groups of the lower Brachycera.

Robber flies have stout, spiny legs and they have three simple eyes (ocelli) in a characteristic depression on the top of their head between their two large compound eyes. They also have a usually dense moustache of stiff bristles on the face; this is called the mystax, a term derived from the Greek mystakos meaning "moustache" or "upper lip". The mystax has been suggested to afford some protection for the head and face when the flies deal with struggling prey; various Asilidae prey on formidable species including stinging Hymenoptera, powerful grasshoppers, dragonflies and even other Asilidae, in fact practically anything of a suitable size. Some Asilidae do, however, specialise in smaller prey, and this is reflected in their more gracile build.