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 liquid 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 



