TABANID^. 



177 



ginal and five posterior cells always present ; basal cells 

 large, anal cell usually closed, but never far before the 

 border of the wing; the marginal vein encompasses the 

 entire wing. Squamae of considerable size. Flies of mod- 

 erate or large size, never slender; rarely with brilliant 

 colors. 



Fig. 64. Pangonia guttata; enlarged. 



This family includes the insects commonl}' called horse- 

 flies, green-headed flies, etc., and has a wide distribution 

 over the world. About eighteen hundred species have 

 received names, of which not less than two hundred and 

 seventy-five are from North America. None of the spe- 

 cies are active on dark, cloudy days, though some are 

 partial to shad}- woods, and are very annoying to stock 

 in such places. On clear, warm days, horseflies begin 

 flying as soon as the sun has warmed the air, and are 

 1 8 



