chaptp:r V 



THE HABITS AND BIONOMICS OF THE HOUSE-FLY 



Local Distribution and Comparative Abundance. 



The local distribution of flies is almost entirely governed by 

 two factors : the presence of breeding places and of food, the 

 former being undoubtedly the most important. This fact is sup- 

 ported not only by my own observations extending over a number 

 of years but by those of such observers as Niven and Hamer who, 

 in particular, have studied the question of the factors governing 

 the local distribution of flies. 



Compared with the other species of flies which inhabit or 

 occasionally visit houses, the house-fly, Miisca domestica, is by far 

 the most abundant. Nevertheless, even in houses a slight varia- 

 tion in the relative abundance of M. domestica and Fannia canicu- 

 laris may be found, for whereas the former will be more numerous 

 in warm places such as the kitchen and dining room where food is 

 present, a large proportion of Fannia canicularis will occasionally 

 be found in the other rooms of houses. In country houses the 

 proportions sometimes vary by the intrusion of Stomoxys calcitrans^. 

 In 1905 in a certain northern country cottage, out of several 

 hundred flies captured, S. calcitrans constituted about 50 per cent, 

 of the total, the rest being chiefly F. canicularis together with a 

 few Anthomyia radicum, whose larvae breed on horse manure with 

 those of M. domestica. 



1 Jennings and King (1918), in discussing the occuiTenee of S. calcitrant in 

 dwellings in South Carolina, U.S.A., state: " Sti'ong preference was shown for the 

 living rooms and in more than half of the houses studied these were the only rooms 

 infested." 



H. H.-F. 5 



