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Bulletin No. 159 



still known to the dwellers on these streams. Apparently 

 it is less common than it was in early pioneer days, when, 

 according to information furnished me, it sometimes ap- 

 peared in early spring in immense swarms, actually killing 

 mules and other stock left unprotected in the bottoms. Yet 

 I cannot find that such an insect is recognized by people 

 living in the mountains where pellagra is prevalent, and 

 although the insect is known to attack man, it seems un- 

 likely that it is the insect agent for conveying the disease. 

 If it were, we ought to find it in Illinois, and throughout 

 Eastern Kentucky where pellagra occurs. Other species of 

 Simulium occur, however, throughout all the territory in 

 which pellagra is known at present, and even if we exclude 

 this species from the problem these others must for the 

 present be considered as possible agents of infection. 



Fig. 4. — Adult of Buffalo gnat. (S. fecuariim) drawn from alcoholic specimen 

 received from Texas, x lo. 



The adult buffalo gnat is a good deal like the black fly 

 in general form, being stout-bodied, the thorax especially 

 prominent and rounded, the legs moderately long, the beak 

 very short but stout. Its two wings are ample, transparent, 



