Robber Fly - Laphria canis
Insect Order: Diptera / Family: Asilidae
Live adult robber flies photographed at DuPage County IL USA.


 

 

There are over 7,000 species of robber flies world wide; nearly 1,000 in North America.  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 much like we vacuum up an ice cream soda through a straw. Many species have long, tapering abdomens, sometimes with a sword-like ovipositor. Others are fat-bodied bumble bee mimics; the effect is quite convincing. Take a close look at any insect that looks like a bumble bee if it's sitting on a leaf - chances are, it's a robber fly. (Bumble bees as a rule do not sit in one spot for more than a few seconds).

 
The robber fly's proboscis is adapted for stabbing and sucking. The large compound eyes provide excellent motion-detection for mid-air intercepts.


 

This robber fly is sucking the bodily fluids from a freshly caught Ichneumon wasp. If you look closely, you can see the proboscis inserted into the head of the wasp. Adult robber flies attack other flies, beetles, butterflies and moths, various bees, dragon and damselflies, ichneumon wasps, grasshoppers, and some spiders. Courtship behavior consists of the male glomming onto the female as if she were prey. Copulation is accomplished tail-to-tail, with the genitalia interlocked. The duo has no trouble flying around in this condition; the male generally towing the female backwards.

Robber Habitat: Pastures, open fields, forest clearings. / Range: North America east of the Rocky Mountains / Food: Adults suck body juices from small flying insects, larvae prey on insect larvae, especially beetles. Adults take their prey on the wing, in mid-air, much like dragonflies and damselflies. Life Cycle: Female lays eggs in holes in the soil. Larvae tunnel downward in search of prey, pupate in soil close to the surface.