“ Little need be said as to the food of the fly itself, as every 
layman is conversant with the feeding habits of this little filth- 
carrying insect. But the contributory part which many authorities 
have claimed that this insect plays in the transmission of zymotic 
diseases is due to the almost persistent habit it has of feeding or 
alighting upon human excreta. 
"In the course of my investigations, more especially on hot days, 
numbers of house-flies were seen hovering over or feeding upon such 
matter. The faeces were generally those of children, and were lying, 
as a rule, a few feet from the doorways in the courts or in the 
passages behind the,houses. In one instance no less than five patches 
of human excreta were lying in one court, and all of these were 
attended by house-flies. 
“Temperature, as has already been stated, has a most marked 
effect upon the developmental cycle of the fly ; and a sudden check 
from heat to cold will materially prolong any one of the stages. Eggs 
hatched in eight to twelve hours in a temperature of from 7 5° to 
8o° F., at a temperature of 6o° F. in twelve hours, but at 45 F. they 
did not hatch until the third day, and then only when placed in a 
warmer temperature for the purpose of studying them under the 
microscope. The larvae or maggots mature in the shortest period in 
fermenting materials at a temperature of between 90° and 98 F., 
but they usually leave the hotter portions of the stable manure when 
it reaches a temperature of ioo° to iio° At 54 0 F. both larval and 
pupal stages are considerably prolonged; larvae kept at this 
temperature had not matured at the end of eight weeks, and a 
number of pupae kept under similar conditions did not produce flies 
until the fourth and fifth weeks. 
“ In this Report I have endeavoured to show that: 
' I-—The chief breeding places of the house-fly are : 
“ (A) Stable middens containing fermenting horse manure or 
a mixture of this and cow dung; 
“ (B) Middens containing fermenting spent hops ; and 
“(C) Ashpits containing fermenting vegetable matter, or about 
25 per cent, of the total number of pits examined. 
“II—That covered ashpits and middens were as badly infested as 
those which were open. 
