THE LESSER HOUSE-FLY 



187 



The Lesser House-fly. Fannia canicnlans L. 



This species (fig. 79) is the less common of the two species 

 of Hies found in liuuses. Its occurrence and frequency are, how- 

 ever, very variable, and no valid explanation has been found so far 

 in my investigations to account for this variability. F. canicularis 

 is more abundant than 31. domestica for a short time during the 

 early part of the summer, usually in May and June. With the 

 beginning of the hot weather the numbers of the latter increase 

 enormously and replace the Lesser House-fly. In many cases which 

 were observed the latter seemed to retreat in small numbers to 

 the rooms of the house not devoted to cooking, and they may 



^^^y 



Fig. 81. Median joints of middle pair of legs (right) ; posterior aspect. 

 a. Fannia scalari><. h. F. canicularis. 



be frequently found flying in a characteristic, jerky and hovering 

 manner around chandeliers, etc., in the living and bed rooms. 

 In country houses, however, they frequently occur in numbers 

 in the kitchens, as an examination of fl^^-traps and papers in 

 such places indicates. An observation recorded by Austen (1911) 

 illustrates the earlier occurrence of F. canicularis as compared 

 Avith M. domestica. Out of a collection of more than 430 flies 

 caught in a kitchen in Leeds, from May 19th to July 18th, 

 only 48 specimens of M. domestica occurred, all the rest being 

 F. canicularis, which outnumbered the former in the ratio of 

 8 or 9-5 to 1. 



