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.
All robber flies have stout, spiny legs and 3 simple eyes (ocelli) in a characteristic depression 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 probably affords 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. In general the family attacks a very wide range of prey, including other flies, beetles, butterflies and moths, various bees, ants, dragon and damselflies, ichneumon wasps, grasshoppers, and some spiders. They do so apparently irrespective of any repugnatorial chemicals the prey may have at its disposal. Many Asilidae when attacked in turn do not hesitate to defend themselves with their proboscides and may deliver intensely painful bites if handled incautiously.
The antennae are short, 3-segmented, and sometimes bear a bristle-like structure called an arista.
The fly attacks its prey by stabbing it with its short, strong proboscis injecting the victim with saliva containing neurotoxic and proteolytic enzymes which very rapidly paralyze the victim and soon digest the insides; the fly then sucks the liquefied material through the proboscis.
Many Asilidae have long, tapering abdomens, sometimes with a sword-like ovipositor. Others, for instance Laphria are fat-bodied bumblebee mimics.
The life histories are poorly known. Larvae generally seem to live in soil, rotting wood, leaf mould and similar materials, some being predatory and others detrivorous.
Read more about this topic: Asilidae