The Two-winged Flies 



343 



states so widely as o cause much alarm. By 1895 it had spread over all 

 of the United States east of the Rocky Mountains. The flies pierce the 

 skin and suck the blood, thus causing such an irritation and loss of blood 

 that the affected animals cease feeding and soon show great loss in milk or 

 weight. The eggs are laid in fresh cow-manure, and the larvae become full- 

 grown and pupate in less than a week. The pupal stage lasts from five 

 to ten days. Probably half a dozen generations appear annually. Infested 



Fig. 488. — The horn-fly, Hiematobia serrala. (After Lugger; natural size indicated 



by line.) 



cattle may be smeared with a mixture of 'resh oil and tar, equal parts, which 

 repels the flies, and lime, which kills the larvae, may be thrown on the manure. 

 The stable-fly, hke the house-fly, lays its eggs in horse-manure, and Dr. 

 Howard foresees a curious benefit to result from the gradual increase in the 

 use of automobiles in cities, and the corresponding decrease in number of 

 horses maintained, in the gradual doing away with the breeding-places of 

 house-flies and stable-flies. 



Next to house-flies the commonest ones about houses and outbuildings 

 are the bluebottles and blow-flies or flesh-flies. These all lay their eggs 

 or deposit living larva; on meat, and, with some other allied species which, 

 however, do not all restrict their egg-laying to animal substances, belong 

 to the subfamily Sarcophaginae, so named from the flesh-eating habits of the 

 larvas or maggots of the best-known species The most abundant flesh- 

 fly in this country is named Sarcophaga sarraceniw (Fig. 489), and looks hke 

 an extra-large house-fly. It gives birth to larvae (hatched from eggs retained 

 in the body of the female) which are deposited on fresh meat, sometimes in 

 open wounds. The larvae (maggots) feed and grow rapidly, attaining their 

 full size in three or four days. They pupate within the thickened brown last 



