328 



The Two-winged Flies 



The most familiar and interesting flies in this group are the well-known 

 horse-flies, gad-flies, or deer-flies, Tabanidae. They are all fairly large, 

 some indeed being among the largest of our flies. 



The great, black, swift horse-flies that in summer dart suddenly at our 

 carriage-horses and with quick shifting flight seem to be fairly carried 

 along in the air close to the horses, are the most familiar representatives of 



FIG. 457. Greenhead, or horse-fly, Tabanus lineola. (After Lugger; natural size 



indicated by line.) 



the order. Many of the smaller horse-flies show gleaming metallic colors, 

 especially about the head. Much of this color is in the large compound 

 eyes, and almost any horse-fly caught alive or just killed will astonish the 

 collector by the brilliant bands and flecks of iridescent green, violet, purple, 



FIG. 458. Diagram of wing of Chrysops sp., a horse-fly, showing venation. 



and copper on the eyes. The biting and blood-sucking are done by the 

 females alone, the males lacking the sharp dagger-like piercing mandibles 

 and contenting themselves with lapping up flower-nectar. 



The brown elongate eggs of horse-flies are laid either on stems or leaves 

 of terrestrial plants, or on aquatic plants or submerged stones. The larvae, 

 whitish, cylindrical, tapering at both ends, and with a series of slightly raised 

 roughened ridges running around the body, either live in water, in slimy 

 places along pond and brook shores, or in soft rich soil, and are predaceous, 



