1910] The Ottawa Naturalist. 33 



it will be seen that with the exception of one year, wherever there 

 has been a rise or fall in the mean temperature for the third 

 quarter of the year, there has been a corresponding rise or fall 

 in the number of deaths: associated with a rise or fall in the 

 temperature would be an increase or decrease in the number of 

 flies, as the two are intimately connected, A high temperature 

 is responsible for a more rapid development of flies, and therefore 

 for an increase in their numbers. The shortest time in which I 

 and other investigators have been able to rear house-flies through 

 all the stages of their life history, that is through the egg, larval 

 or maggot and pupal stages, is slightly over eight days by keeping 

 them at a constant high temperature. It was also found that in 

 ten to fourteen days these flies could lay eggs. As each fly is 

 eatable of laying from 120 to 150 eggs in a single batch, and 

 ma\ lay six or even more batches of eggs during its life, it is an 

 easy matter to understand how a single fly may be responsible 

 for an incredible number of descendants during a single season, 

 and in the light of these facts, the enormous number of flies 

 present in a hot season ceases to be a matter of wonder, and still 

 more so when it is learnt "where they all come from." 



The chief and favourite breeding place of the house-fly 

 is in stable refuse, which may sometim.es be found to be 

 literally alive with the "maggots" of the house-fly. In a city 

 like Ottawa where stables are located behind houses in almost 

 every street, and each single horse stable has its pile of refuse, 

 is it to be wondered at that house-flies are so numerous? It is 

 little use complaining about these pests, and potentially the, 

 most dangerous pests we have, while such conditions are allowed 

 to exist. A single refuse heap will supply a whole street with 

 flies; a single, unclosed, and not frequently emptied refuse bin 

 will colonise a house, for they breed in incredible numbers in 

 waste and decaying vegetable products, such as accumulate in 

 the household refuse bin. All decaying and excremental sub- 

 stances, provided the temperature is suitable, serve as breeding 

 places for house-flies, and in these facts lies the solution to the 

 house-fly problem which we are compelled to face if we would 

 reduce the infantile mortality rate and the death rate of typhoid 

 fever. There are two ways of dealing with a nuisance, the one 

 is to abolish it ; the other to render it innocuous. Boards of 

 health and local authorities should make it illegal to keep stable 

 refuse exposed for more than six days, that is, a period of time 

 less than that required by the fly to pass through its complete 

 development from egg to fly. Within that time it should be 

 compulsorily removed to well without the boundaries of the 

 city. Refuse bins should be similarly treated. Refuse should 



