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DIPTERA, Asilidae (Leach 1819) -- <Images> & <Juveniles>

The Asilidae are commonly called robber flies. The family Asilidae contains about 7,100 described species worldwide.

All robber flies have stout, spiny legs, a dense moustache of bristles on the face (mystax), and 3 simple eyes (ocelli) in a characteristic depression between their two large compound eyes. The mystax helps protect the head and face when the fly encounters prey bent on defense. The antennae are short, 3-segmented, sometimes with a bristle-like structure called an arista.

The short, strong proboscis is used to stab and inject victims with saliva containing neurotoxic and proteolytic enzymes which paralyze and digest the insides; the fly then sucks the liquefied meal through the proboscis. Many species have long, tapering abdomens, sometimes with a sword-like ovipositor. Others are fat-bodied bumblebee mimics. Adult robber flies attack other flies, beetles, butterflies and moths, various bees, ants, dragon and damselflies, Ichneumon wasps, grasshoppers, and some spiders.

Adults lay eggs into soil or plants. The larvae are often found in decaying organic matter, such as dung heaps and rotting logs, but are also found in ordinary soil. In most species the larvae are omnivorous and are known to eat the eggs and larvae of other insects. Their life cycle ranges from 1 to 3 years.

References: Please refer to <biology.ref.htm>, [Additional references may be found at: MELVYL Library]

Cole, F. R. 1969. The Flies of Western North America. Univ. Calif. Press, Berkeley & Los Angeles. 693 p.

Hull, F. M. 1962. Bull. U. S. Nat. Mus. 224: 1-430.

Martin, C. H. 1957. Bull. Amer. Mus. Nat. Hist. 111: 345-85.

Melin, D. 1923. Uppsala Univ. Zool. Bidr. 8: 1-317.

Ritcher, P. O. 1940. Kentucky Agr. Expt. Sta. Bull. 401: 73-157.