SOME ANNOYING PESTS OF MAN 335 



THE BLACK-FLIES 



Simulium venustum et al. 



The black-flies, although not strictly household insects, 

 are yet very annoying to people living in certain parts of 

 the United States especially in certain wooded areas of the 

 more northern latitudes. The black-flies are also very 

 troublesome to campers, summer residents, lumbermen, 

 and hunters, whenever they invade the territory of these 

 insects during the breeding season. Moreover, a noted 

 worker, Sambon, has come to the conclusion, from certain 

 careful observations he has made, "that a minute blood- 

 sucking fly of the genus Simulium is, in all probability, the 

 agent by which pellagra is conveyed." The fact that the 

 dreaded disease pellagra, which seems to be growing more 

 common in the United States, may be distributed through 

 the agency of black-flies has aroused much interest in these 

 insects. All of the black-flies with which we are concerned 

 belong to the genus Simulium. 



Description, distribution, and habits of black-flies. — 

 These insects are members of the order Diptera, and the 

 females have strong piercing and sucking mouth parts. 

 The mouth parts of the males are not so well developed 

 and seem incapable of drawing blood. The black-flies 

 have short, stout, black bodies with broad wings and a 

 hump-shouldered appearance, due to the head's being bent 

 under the large humped thorax. They are all small, 

 varying in length from -$% to \ of an inch. They are 

 remarkable for the immense numbers in which they swarm 

 from streams in early spring and for the fierceness and 

 persistence with which the females of certain species punc- 



