Eye of a large robber fly. The picture has been made with magnification factor 8 and f/11, using a Canon 7D and the Canon macrolens MP-E 65mm/f2.8. The fly was alive and doing its business when the picture was made in our garden. It is a slingle picture made without using a tripod.
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. 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 (source: Wikipedia).
From Hunting flies