176 



SCHOOL ENTOMOLOGY 



flies that infest dwelling houses, both in cities and on farms, 

 a vast proportion come from horse manure." (Howard.) 

 Where horse manure is not available it commonly breeds in 

 other manure or in fermenting vegetable material or slops. 

 The eggs hatch in about twenty-four hours, the larvae 

 or maggots become grown in from five to seven days, and 

 the pupal stage lasts about the same time, so that a complete 

 generation may develop in from ten days to two weeks, de- 

 pending upon the temperature. Each female lays about 



FIG. 125. The common house fly (Musca domestica) . (After Howard, 

 U. S. Dept. Agr.) 



Puparium at left; adult next; larva and enlarged parts at right. All enlarged. 



120 eggs in a batch and may lay four times, so that it is 

 evident that the species multiplies with extreme rapidity. 

 The adult flies hibernate over winter in attics, barns, etc., 

 and the pupae may hibernate in the soil or under manure or 

 straw. It is evident, therefore, that the first flies which 

 appear in the spring should be vigorously combated so as 

 to prevent the countless numbers to which they will give 

 rise later. 



"In army camps, in mining camps, and in great public 

 works, bringing together large numbers of men for a longer 

 or shorter time, there is seldom the proper care of excreta, 



