l6 FLIES FOUND IN HOUSES 



The relative frequency of different species of flies in houses. 



During the last few years a number of workers have examined 

 the flies caught in houses in fly traps or on fly papers, and have 

 conclusively shown that the species most commonly caught is 

 the house-fly {M. domestica). In considering such results it 

 must be remembered several species are not attracted to traps 

 or papers and are therefore not taken into consideration in such 

 statistics. Most of these, however, are probably of little im- 

 portance. 



Hewitt (1910, p. 349) during a number of years made 

 observations in town and suburban houses and country houses 

 and cottages, and found that in the former M. domestica was by 

 far the commonest fly. " But whereas M. domestica may be the 

 only species in warm places where food is present, such as 

 restaurants and kitchens, in other rooms of the house F. cani- 

 cularis, the lesser house-fly, increases in proportion and often 

 predominates. In country houses the proportions vary by the 

 intrusion of Stomoxys calcitrans." In certain country houses 

 5. calcitrans may form 50 "/o of all the flies, the rest being chiefly 

 F. canicularis and A. radicum. 



The following records are taken from a ' fly census ' made 

 by Hewitt in 1907, and may be taken as illustrative of the 

 proportional abundance of the different species in different 

 situations. 



TABLE I. 



Place M. domestica F. canicularis Other species 



Restaurant, Manchester 1869 (99 "/o) 14 (I'Vo) ^ 



Kitchen, suburban house, Manchester 682(9770) 7 ( • "/o) '4 (^%) 



„ Lancashire 581 (67%) ^65 (30 '7o) 14 l^'/o) 



Bedroom, suburban house i (.^%) 3.^ (8? "/o) 4(io7o) 



Stable „ „ 22(i2»/o) i5.^(8i7o) H (7%) 



3 '55 (85-8 7o) 47 Mi 2-8 7o) 48(1 -370) 



These figures are small and relate to different localities in the 

 same neighbourhood, but larger figures are available of the 

 collections formed by various workers in England and by 

 Howard in the United States in houses and places where food 

 is exposed. The results are recorded in the following table. 



