The Gad-Flies or Horse-Flies 



and his experiments resulted in the destruction of great numbers 

 of Tabanids. 



The larvae of the Tabanidae live in the earth or in water and 

 are carnivorous, feeding upon soft-bodied insects and water 

 snails. The spindle-shaped brown or black eggs are deposited 

 in summer in groups attached to the leaves or stems of herbage. 

 The gad-flies vary greatly in color and size, and the smaller ones 

 of the genus Chrysops, sometimes called "deer flies," are fre- 

 quently quite small and colored with yellow or green. The 

 larger ones vary through gray and brown to black. Our largest 

 gad-fly is Tabanus americanus Forst., which is an inch and a 

 quarter long, and has a wing-spread of two and one-half inches. 

 It inhabits the Southern States. About 1,500 species are known, 

 and perhaps 200 occur in this country. 



Typical Life History of a Gad-Fly 



(Tabanus atratus Fab.^ 



This is one of the common large black horse-flies which has 

 a very wide distribution in the United States. Its larvae have been 



studied by Walsh, 

 Riley and Hart. Hart 

 has found the egg 

 masses in July on the 

 dry bark of a stick 

 projecting from the 

 water. From these 

 eggs larvae hatched 

 August 4th. Larvae 

 of this species were 

 found commonly in 

 water, among vege- 

 tation and in the sand 

 of the sandy shores 

 of the Illinois River. 

 Pupae may be found 

 in the early summer, and the adults appear from May to July, 

 living all through the summer. The species is apparently 

 single-brooded, that is to say, has but one generation annually, 



Fig. 75. — Tabanus atratus: a, larva; b, pupa; 

 c, adult. (After Riley.) 



