The Two-winged Flies 
3 1 3 
decaying seaweed, etc., and from among these this species has no doubt 
gradually worked its way out to the very verge of the shore-line, becoming 
gradually adapted in habit and structure to the conditions of its new 
habitat. 
Besides the mosquitoes and punkies a third kind of fly assails the rod- 
and-line fisherman, the hunter, and the camper in forests and along the streams; 
black, stout-bodied, hump-backed, short-legged, broad-winged flies (Fig. 
424) from one-sixth to one-fourth of an inch long, with short but strong 
piercing proboscis. These are black-flies, buffalo-gnats or turkey-gnats, as 
they are variously called, composing the small family Simuliidae, distributed 
all over this country, but especially abundant in the southern states, where 
they attack cattle so fiercely and in such great swarms that the animals are 
driven frantic and sometimes even killed by a violent fever produced by the 
terrible biting. 
The larvae (Fig. 426) are odd, squirming, slippery, little black “worms,” 
which, clinging by the hind tip of the body, occur in dense colonies or patches 
Fig. 427. 
Fig. 428. 
Fig. 427—Mouth-parts of female black-fly, Simulium sp. lep., labrum; hyp., hypo- 
pharynx; md., mandible; mx., maxilla; mxp., maxillary palpus; li., labium; pg., 
paraglossa. (Much enlarged.) 
Fig. 428. Mouth-parts of larva of black-fly, Simulium sp. lb., labrum; ep., epipharynx; 
md.., mandible; mx., maxilla; mxp., maxillary palpus; mxl., maxillary lobe; li., 
labium; hyp., hypopharynx. (Much enlarged.) 
with a conspicuous pair of freely movable brushes which collect food from 
the water. The clinging to the rock is effected by means of silk spun 
from the mouth, and by the skilful use of silken threads the larvae can 
move about over the submerged rock bed without being washed away by 
the swift water. When ready to pupate, which is after about a month of 
