410 



SCIENCE OF HOME AND COMMUNITY 



of manure piles has shown that on the average a pound of 

 manure may have from 500 to 1000 larvae in it. The fly in 

 its development passes through the four stages of egg, larva, 

 pupa, and adult. About one hundred and twenty eggs are 

 laid at a time by one female and this may be repeated four 

 times in a season. The eggs hatch in a day or less; the 

 larval state, the maggots, lasts from five to six days ; and 

 the pupal state from five to seven days. Thus the entire 

 period of development takes from ten to fourteen days, 

 being more rapid in the warmer seasons and climates. 



Larva Pup o A du/t 



FIG. 162. Life history of the house fly. 



The females begin to lay eggs in from ten to fourteen 

 days after emerging from the pupal state. Egg-laying begins 

 in the spring and continues till the cold days of autumn. 

 During this period it is possible to have from eight to twelve 

 generations. It is thus seen that possibilities of increase 

 during a single season are enormous. On the approach of 

 cold weather most of the flies die, but a few hibernate for 

 the winter, some as adults in cracks and crevices of build- 

 ings and a few in the puparium state. 



3. CONTROL OP FLY 



The most effective fly campaign requires the cooperation 

 of citizens, health officers, and town authorities. It is 



