342 
The Two-winged Flies 
Most abundant, most wide-spread, and most important to us of all the 
Muscid flies are the common house-flies. They belong with some other 
similar forms to the subfamily Muscinae. A number of species may be 
found in houses, but the true house-fly, Musca domestica (Fig. 483), is by 
far the most numerous. Dr. Howard, government entomologist, who has 
paid special attention to the life of house-flies and mosquitoes, because of 
their dangerous disease-germ carrying habits, says that house-flies undoubtedly 
contribute materially in the dissemination of infectious diseases by carrying 
germs in the dirt and filth on their feet, collected during their pilgrimages 
to the contents of cuspidors, slop-pails, and closets. He advocates a definite 
crusade against the house-fly like the one now being undertaken in this, 
country against the mosquito. 
Fig. 485. 
Fig. 486. 
Fig. 485.—Larva of house-fly, Musca domestica. (After Howard and Marlatt; three 
times natural size.) 
Fig. 486.—Pupa, in puparium, of house-fly, Musca domestica. (After Howard and 
Marlatt; three times natural size.) 
The eggs of the house-fly are laid in horse-manure, occasionally in other 
excrementitious or decaying matter. Each female lays about one hundred eggs. 
These eggs hatch in six or seven hours, and the slender pointed white larvae 
called maggots (Fig. 485) lie in their plentiful food-supply for the five or six days 
necessary for their full growth. They pupate within the last larval skin, which 
thickens and turns brown at the time of pupation 
(Fig. 486). The pupal stage lasts five days, and 
then the fly issues. Its food is liquid and taken 
up by lapping. The ‘‘house-fly” that bites is 
not the true house-fly, but usually the fiercely 
piercing stable-fly, Stomoxys calcitrans, another 
member of the subfamily, which looks much like 
Musca and which is a not infrequent visitor in 
the house. 
Fig. 487.—A stable-fly, Sto- This stable-fly and another ally of the house- 
moxys calcitrans. (Three fly ? called the horn-fly, are great pests of stock, 
times natural size.) The horn-fly, Hcematobia serrata (Fig. 488), which 
gets its popular name from the habit of clustering, when not feeding, on the 
bases of the horns of cattle, is a European insect that was accidentally brought 
to this country in 1886 or 1887. 
It quickly established itself, and in two years had spread over the eastern 
