THE HOUSE PLY. 



WHERE THE TRUE HOUSE FLY LAYS ITS EGGS. 



Tlie true house fly (fig. 7), which is found in nearly all parts of the 

 world, is a medium-sized fly with four black stripes on the back and 

 a sharp_ elbow in one of the veins of the wings. The house fly can 

 not bite, its mouth 

 parts being spread out 

 at the tip for sucking 

 up liquid substances. 



Tlie eggs (figs. 8,9) 

 are laid upon horse 

 manure. This sub- 

 stance seems to be 

 its favorite larval 

 food. It will breed 

 also in human excre- 

 ment, and because of 

 this habit it is very 

 dangerous to the 

 health of human beings, carrying as it docs the germs of intestinal 

 diseases, such as typhoid fever and cholera, from the excreta to food 

 suppHes. It has also been found to breed freely in hog manure and 

 to some extent in cow and chicken manure. Indeed, it will lay its 

 eggs on a great variety of decaying vegetable and animal materials. 



'little house fly" {Fannia brevis): Female at left, male 

 at right. Much enlarged. 



Fig. 6.— The vinegar fly (Drosophila ampehphila). 

 Much enl.ir.'Tod. 



Fig. 7.— The true house fly ( Mus- 

 ca domestica). Enlarged. 



but of the flies that infest dwelling houses, both in cities and on 

 farms, a vast proportion come from horse manure. 



It often happens, however, that this . fly is very abundant in 

 localities where little or no horse manure is found, and in such cases 

 it breeds in other manure or in sloi)s or fermenting vegetable material, 

 such as spent hops, moist bran, ensUage, or rotting potatoes. Accu- 

 mulations of organic material on the dumping grounds of towns 

 and cities often produce flies in great numbers. 



