2g2 



Marvels of Insect Life. 



that issue from them set to work with all speed to reduce the most offensive portion 

 of the nuisance. In less than a week they have done what they could, and have 

 become full grown. They turn to chrysalids inside the maggot skin, and in another 

 week they are flies. These lay their eggs, thus ensuring the continuation of the 

 sanitary work by a vastly increased host of workers, and then, attracted by various 

 odours, enter our dwellings for a brief life of enjoyment, partaking of infinitesimal 

 portions of our food, licking up the microbes we foster but do not want, and perhaps 

 coming to an end in the milk-jug or jam-dish, whose contents thereby become 

 impregnated with germs. 



It must not be supposed from what has been said that the house-fly confines 



its attention to stable manure as an egg- 

 laying ground and nursery for its progeny. 

 It feeds in any organic waste that is suffi- 

 ciently warm and moist to ferment, but 

 mainly in horse manure, human manure, 

 pig manure, spent hops, and malt-waste 

 (brewer's grains). Each female fly lays 

 several batches of eggs, in all about six 

 hundred, which hatch in periods varying 

 with the conditions at the time — often 

 eight hours, sometimes four days. The 

 newly hatched " maggot " at once burrows 

 into the refuse, seeking the moister parts 

 that it may feed upon the liquid portion. 

 The most favourable temperature for deve- 

 lopment appears to be between 90°-98°. 



Dr. L. O. Howard, who has written a 



terrible indictment of the house-fly — which 



he prefers to call the typhoid-fly — has made 



a calculation of the progeny of a single 



[//. Ba-,im. female fly that, having passed the winter in 



Plinto by] 



PUPARIA OF HoUSE-FlY. 



some snug spot, 



April 15th. By 



the living issue 



5,598,720,000,000 ! 



the eggs laid do 



begins 



layin 



S: eggs on 



the loth of September 

 of that fly will be 

 Of course, in fact, all 

 not produce maggots. 



Tlip grub of the house-fly, instead of casting its skin when 

 it turns to a chrysalis, merely detaches itself from the skin, 

 which becomes a hard and dark red barrel protecting the 

 delicate white chrysahs. This case is known as the 

 puparium. To escape, the newly formed fly blows out 

 a bladder on its head, which pushes off one end of the 

 puparium and allows its exit. 



all the maggots hatched do not survive to become flies, all the flies are not females, 

 and all the female flies do not become mothers ; but to eliminate failure of this sort 

 he reckons that half a generation consists of females and that each female lays 

 only one hundred and twenty eggs, instead of her maximum of six hundred. He 

 shows that, in the United States at least, typhoid, cholera infantum, and " summer 

 complaint " are chiefly spread by these flies carrying the germs from the sick to the 

 well. Most other complaints that flesh is supposed to be heir to are greatl}^ assisted 

 in their spread by the same agency. Several English authorities on sanitation have 

 made similar declarations as the result of their investigations. 



