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, 
