THE HOUSE FLY. 



Fig. 11.— Pupae of the house fly. About natural size. (Newstead.) 



The second way in which the house fly may pass the whiter is by 

 continuous breeding. As is well known, house flies congregate in 

 heated rooms with the approach of the winter season. If no food or 

 breeding materials are present they eventually will die. Where they 

 have complete access to food they may persist as late as the end of 

 January. However, where they have access to both food and suit- 

 able substances for egg laying they will continue breeding just as they 

 do outdoors during the summer. Rearing experiments have been 

 conducted in a bakery, in greenhouses, and in animal breeding 

 houses during winter seasons. Even in very cold climates there 

 are undoubtedly many places, especially in cities, where house flies 

 would have opportunit}^ to pass the winter in this manner. 



CARRIAGE OF DISEASE BY THE HOUSE FLY. 



The body of the house fly is covered thickly with hairs and bristles 

 of varying lengths, and this is especially true of the legs. Thus, 

 when it crawls over infected material it readily becomes loaded with 

 germs, and subsequent visits to human foods result in their contami- 

 natioUo Even more dangerous than the transference of germs on the 

 legs and body of the fly is the fact that bacteria are fomul in greater 

 numbers and live longer in the alimentary canal. These germs are 

 104410°- Bull. 851—17 2 



