SOME ANNOYING PESTS OF MAN 



341 



One wonders if a person, forced to remain on an island 

 all day with these pests and without a smudge for protec- 

 tion, could survive the attacks of these northern black- 

 flies. 



Life history of a black-fly. — The life histories of most 

 of our black-flies are very imperfectly known. The species 

 (Fig. 116) S. pictipes occurs 

 abundantly in the streams in 

 the vicinity of Ithaca, New 

 York. In the summer of 

 1889 Miss R. O. Phillips 

 studied the life history of 

 this species in detail, but 

 her results embodied in a 

 thesis have never been pub- 

 lished. The following ac- 

 count of this black-fly based 

 upon Miss Phillips's work will 

 serve as generally repre- 

 sentative of these insects. 



The female flies hover in 

 small swarms over a thin 

 sheet of swiftly flowing 



water. Now and then one darts downward and quickly 

 fastens an egg to the surface of the rock beneath the 

 water. The eggs are light yellow at first and are laid 

 in patches a foot or more in diameter. The eggs, which 

 soon turn brown after being deposited, depend upon 

 sunlight for their development. Under favorable con- 

 ditions they begin to hatch in about eight days. The 

 larvae are long and slender, more or less cylindrical in 

 shape, although smaller in the middle and blackish in 



Fig. 116. — A black-fly (S pic- 

 tipes). (X 10.) 



