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, Hczmatobia serrata. (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, like 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 larvae 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 
larvae or maggots of the best-known species The most abundant flesh- 
fly in this country is named Sarcophaga sarracenice (Fig. 489), and looks like 
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 
