y6 HABITS 



it was often not easy to catch flies on the tip itself, but they 

 could be caught in any numbers in the shelter, when some 

 sacking, which covered the wall, and a bench near the stove, 

 was sometimes literally black with them. Though the flies 

 caught in the workmen's shelter, like those caught in the village, 

 were practically all M. doinestica, this must be due rather to 

 the habits of this fly than to the failure of other species to breed 

 on the tip, since the collection of 200 lar^■a; and pupa; from fresh 

 tip refuse gave the following results. 



" A considerable number of undetermined PJiorida; were also 

 bred out from samples of the refuse, which were kept as likely 

 to be good for some of these larvee. 



" We see, therefore, that there was a considerable variety 

 among the flies breeding in the refuse ; just as on the sewage 

 farm (near by) Sepsis and Scatophaga were the dominant species, 

 so M. doinestica predominated on the refuse heap." 



These observers came to the conclusion that the tip did not 

 attract flies for several reasons : marked flies did not return to 

 it, eggs and young larvae were not found on it, female flies did 

 not predominate, and an examination of the fresh refuse showed 

 that it already contained many larvae and also pupje. The tip 

 was therefore a distributing centre of flies. On general grounds 

 there is every reason to believe that the flies which infested the 

 village were bred in the refuse heap and migrated from it, and 

 further the investigators proved this experimentall}'. Flies were 

 marked by shaking in a stout paper bag containing a small 

 ■quantity of coloured chalk (using, as a rule, a different colour 

 for each day) and liberated at the refuse heap. Some of these 

 were subsequently found at the village. Other similar experi- 

 ments showed that some of the flies occasionally travelled as far 

 as 1700 yards, and that distances of 800 to 1000 yards were 

 often traversed. Two marked flies were caught 800 }-ards from 

 the refuse heap 35 and 45 minutes respectively after liberation. 



