SANITARY OFFICERS 243 



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 the jam- dish. 



It must not be supposed from what has been said 

 that the House Fly confines its attention to the 

 heap of stable-manure as an egg-laying ground and 

 nursery for its progeny. It feeds in any organic 

 waste that is sufficiently warm and moist to fer- 

 ment, 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 mass 

 of refuse, seeking the moister parts that he may 

 feed upon the Hquid portion. The most favourable 

 temperature for development appears to be between 

 90° to 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 female fly that, having 

 passed the winter in some snug spot, begins laying 

 eggs on April 15. By September 10 the living 

 issue of that fly will be 5,598,720,000,000 ! Of 

 course, in fact, all the eggs laid do not produce 

 maggots, all the maggots hatched do not survive 



