188 THE LESSER HOUSE-FLY AXD THE LATRINE-FLY 



The numerical abundance of F. caniculans in comparison with 

 the abundance of M. domestica varies considerably. In a collec- 

 tion of 4000 flies which I made in different situations, such as 

 kitchens, restaurants, bed-rooms, etc., in 1907, this species formed 

 11 "5 per cent, of the total number. In 1900 Howard found that 

 in collections made in different cities of the United States only 

 about 1 per cent, of a collection of over 28,000 flies made in 

 rooms where food was exposed were F. canicularis, and over 

 98 per cent, were M. domestica. Hamer in 1908, in collections 

 made in kitchens and " living rooms " of houses near depots for 

 horse-manure in London, found that the percentage of F. canicu- 

 laris varied from 17 per cent, to 24 per cent. Niven gives the 

 results of collections made at six different stations in Manchester. 

 The total number of flies caught was 8553, of which 8196 were 

 M. domestica, 293 F. canicidaris, and 64 were other species. 

 Thus F. canicidaris constituted 3'4 per cent, of the total of the 

 fly population. Robertson (1909) gives the results of similar 

 collections made in Birmingham where, of 24,572 flies caught, 

 91 per cent, were M. domestica and 4'7 per cent, were F. canicu- 

 laris. From observations which I have made in many localities 

 in different neighbourhoods, I do not think that this species 

 would often form more than 25 per cent, of the total fly popu- 

 lation. After M. domestica, however, it is the next fly of 

 importance inhabiting houses, and well deserves the title of the 

 Lesser House-fly. It is known in Germany as "die kleine 

 Stubenfliege." 



The male of F. canicularis differs from the female in some 

 respects. In the male the eyes are close together, and the 

 frontal region is consequently very narrow ; the sides of this, 

 which are the inner orbital regions, are silvery white, separated 

 by a narrow black frontal stripe. In the female the space 

 between the inner margins of the eyes is about one-third of 

 the width of the head ; the frons is brownish black, and the 

 inner orbital regions are dark ashy grey. The bristle of the 

 antenna of F. canicularis is bare ; in M. domestica, it will be 

 remembered, the bristle bears a row of setae on its upper and 

 lower sides. The dorsal side of the thorax of the male is 

 blackish grey with three rather indistinct longitudinal black 



