78 HABITS 



The only observations hitherto pubHshed on the flight of flies 

 in cities lend support to the last statement of Hine. Cox, Lewis 

 and Glynn (191 2, p. 309), working in Liverpool, came to the 

 conclusion that " in cities where food is plentiful flies rarely 

 migrate from the localities in which they are bred " (see 

 Chapter x). 



The larger species of house-frequenting flies can probabh" 

 travel much further than the house-fly and other smaller species, 

 if we may judge from the extraordinary powers of flight of some 

 of the gad-flies of the family TabanidcE, which can circle round 

 fast trotting horses only alighting occasionally. 



B. Outdoor habits. 



In Chapter II it has been shown that most of the flies 

 commonly found in houses breed in various decaying substances 

 and excreta, and consequently the adults, especially the females, 

 seek these substances for the purpose of depositing eggs, and at 

 the same time walk over them and not infrequently feed on 

 them. Though M. domestica, M. stabulans, and Drosopliilid<2 

 prefer to lay their eggs on fermenting vegetable matter, they also 

 deposit them on horse manure and other excreta. F. cauicnlaris, 

 F. scalaris, P. rudis, A. radiciun, SepsidcE and the PsycJiodida 

 prefer the latter. The larvje of the larger flies, Lucilia, Calli- 

 pJiora and SarcopJiaga feed on carrion, and the flies are attracted 

 to such materials. 



In fact most of these species are attracted to filth of all 

 kinds. They are also frequently found feeding on over ripe 

 fruit, both on trees and when exposed for sale in shops, and 

 certainly contaminate it with fascal and putrefactive bacteria. 

 Many of them are also attracted to meat, both cooked and raw, 

 milk, butter, sweets and other food materials exposed in shops 

 and on stalls. 



"In order to determine the distribution of the sexes" Hermes 

 (19 II, p. 521) made observations "under two different conditions, 

 viz. first, six sweepings with an insect net were made over a 

 horse manure pile on which many flies had gathered ; second, 

 flies were collected in one house, giving a fairly representative 

 lot for indoors." 



