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ELEMENTS OF GENERAL SCIENCE 



hatch in from six to eight hours, forming larvae. The larvae 

 do not look like flies (fig. 51). They are small, white, worm- 

 like creatures, but of course 

 they are really insects and 

 not worms. They are called 

 maggots. For about five 

 days they feed upon the 

 refuse in which the eggs 

 were laid, after which they 

 become quiet and change 

 into pupse. After five or 

 six days the pupse trans- 

 form into adult flies. In a 

 few days these flies lay 

 eggs, and another genera- 

 tion is begun. In ten days 

 1 20 flies may develop from 

 one pair of house flies. 

 Suppose that half the flies 

 of the second generation are 



females and that they lay eggs within two days. At that rate, 

 how many flies might be produced from a single pair during 

 four summer months ? 



FIG. 50. The house fly 



The rough and hairy body of the fly is well 

 adapted to carrying bacteria. After Howard 



FIG. 51. Life history of the house fly 

 A, egg; B, larva; C, pupa; D, mature fly 



