140 ENTOMOLOGY FOR MEDICAL OFFICERS 



Family AsiLlD^: Robber-flies (Fig. 45), Lat. Asilus = a. 

 horse-fly). Usually bristly, elongate flies — but sometimes 

 thickly hairy and bee-like — with remarkably long, strong, 

 bristly legs. The head is broad and short, joined to the 

 thorax by a very distinct and mobile neck, and deeply 

 notched on the crown between the eyes. Antennae composed 

 of 3 simple segments, with or without a terminal bristle or 

 style. Proboscis strong, chitinous, and pointed ; formed for 

 stabbing. Abdomen of 8 segments, with the genitalia con- 

 spicuous. Empodium bristle-like, or absent ; pulvilli usually 



Fig. 45.— Eobber-fly. 



distinct, claws strong. Wing-venation complex, with two or 

 three submarginal and five posterior cells. Squamse small. 



The Robber-flies are one of the largest families of 

 Diptera, and are found in all parts of the world. Some of 

 them are very large. They live entirely upon other insects, 

 swooping upon them and impaling them with their proboscis, 

 and then flying off with them clasped in their legs, to suck 

 them at leisure. A robber-fly will often thus treat an insect 

 much larger than itself Robber-flies have been said to suck 

 blood occasionally, and several medical officers from Africa 

 have stated that they have been thus attacked, but this 

 behaviour is not usual. 



Family Therevid^ (Q)^pevew = to hunt). The flies of this 



