THE HOUSE FLY 7 



microbes of various animal diseases to our stock, and in 

 consequence we are making strenuous efforts to kill these 

 ticks by dipping, burning the herbage, preserving bird life, 

 &c. ; but so far, at least in this country, we have done 

 little or nothing to kill the fly which is sowing disease and 

 death in town, village, and kraal. 



The House Fly lays about 150 eggs on dung, in garbage 

 heaps, and in all kinds of decaying vegetable and animal 

 matter. The eggs hatch out into tiny white grubs, usually 



FIG. 2. 



EGG OF A HOUSE FLY. Batches of 150 and more 

 are laid in garbage heaps and any other kind 

 of animal and vegetable filth. (Enlarged.) 

 (From the National Geographic Society, Washington, D.C. 

 Copyright, 1913, by special permission.) 



in about twelve hours ; these at once begin to feed greedily 

 on the decaying refuse or stale meat, as the case may be. 

 In from five to eight days, in favourable conditions, 

 the maggots are fully developed and immediately change 

 into the chrysalis condition. In another week, some- 

 times less, they issue forth as full-grown House Flies. 

 These in the course of a few days lay batches of eggs, and 

 so the cycle goes on. In mid-summer the whole life cycle 

 only takes about ten days. A single fly can in one summer 

 season be the progenitor of countless billions, each of which 

 is capable of carrying from one to many thousands, and 



