HEALTH AND WELL-BEING 



59 



in a pile of horse manure, and in about five days change to 

 the pupa stage. In another week the full grown flies emerge, 

 and the cycle of changes is repeated. Thus it is that in about 

 two weeks one hundred eggs may become .one hundred flies. 

 As each female may lay four lots of eggs in a season it is 

 possible for a single fly to be multiplied into millions between 

 spring and fall. 



PIG. 24. The house fly. 



Control of the menace from flies lies in the fact that rela- 

 tively few flies live through cold winter seasons, and that they 

 do not go far away from their breeding places. The survi- 

 vors in the spring may be trapped and the conditions for 

 breeding may be made unfavorable throughout the season. 

 Piles^of refuse about stables, and of decaying organic matter 

 anywhere, are favorite breeding places. Any successful 



