Insects in the Diptera family 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. Adult robber flies attack other flies, beetles, butterflies and moths, various bees, ants, dragonflies and damselflies, wasps, grasshoppers, and some spiders.
Photos: DFNP, Singapore 20120521