14 THE HOUSE FLY— DISEASE CARRIER 



manure, he found that there were only two such ac- 

 cumulations on the hospital grounds. The one at the 

 stable was in a large masonry pit drained below and 

 covered so that while not fly-proof it was dark and dry. 

 No larvae or puparia were found in the pit. The ma- 

 nure was molding and heating rapidly. Two other 

 piles where the manure was kept dry and in the dark 

 showed the same condition of rapid heating and mold- 

 ing and no larvae were found. At the farm barn the 

 manure was dropped through four traps where a pile 

 accumulated, and was then taken to the part of the 

 barn where the cow manure is collected and the two 

 were mixed together. Here a considerable number 

 of larvae and puparia were found, but not in sufficiently 

 great numbers to account for the swarms around the 

 buildings. They were more abundant in the part of 

 the pile which consisted of pure horse manure and 

 grew noticeably less until the cow manure was reached, 

 when they were very few. Examination of the pig 

 pen showed piles of pig manure mixed with the straw 

 bedding exposed to air and rain. This was badly in- 

 fested ; one ounce of material taken from a point a few 

 inches below the surface displayed 868 puparia. An- 

 other prolific source was found in piles of spent hops 

 and barley malt — brewery waste which had been hauled 

 in as a fertilizer. The hops showed a tendency to mold 

 rapidly, and the flies did not breed in it as abundantly 

 as in the looser barley malt. In parts of the malt where 

 there was plenty of moisture the maggots were ex- 

 tremely numerous; one ounce contained i,oi8 mag- 



