HABITS 75 



The first series were undertaken by Arnold (1907, p. 262), 

 who liberated from the window of the Administration Block 

 of the Monsall Hospital, Manchester, a hundred flies marked 

 with a spot of white enamel on the thorax, on three successive 

 Sundays. This form of marking did not affect the energy of the 

 fly, and the mark did not readily wear off. The fly traps in the 

 wards were then watched for the marked flies. " Of the 300, five 

 were recovered at distances varying from 30 to 190 yards. The 

 liberations were always in fine weather, and the recoveries were 

 within five days. In this experiment 190 yards was the greatest 

 distance available, so that the experiments cannot be taken as 

 giving any hint of the limit of range." 



In the case of the biting fly, Glossona morsitans, the investiga- 

 tions of Bagshawe (1908) show that marked flies maybe retaken 

 up to 900 yards from the point of liberation. 



A more extended series of observations were carried out by 

 Copeman, Howlett and Merriman (191 1) in 1910 at Postwick, 

 a small village, situated about five miles east of Norwich, the 

 inhabitants of which " were experiencing a plague of flies, so 

 unprecedented in extent as to constitute a serious annoyance, 

 and possible danger to health." More than 99 per cent, of the 

 flies caught on the village fly papers were AT. domestica and the 

 remainder mostly F. caniadaris. " As the result of careful 

 investigations in the village itself, in which there existed no 

 unusual accumulation of manure or other fermenting refuse, we 

 came to the conclusion that no special opportunity was afforded 

 there for the breeding of the house-fly in such quantities as 

 had been present. It became obvious, therefore, that special 

 conditions must be in operation, affording a reservoir of flies at 

 some situation outside the village boundaries. Such conditions 

 were afforded by the presence of enormous accumulations of 

 dust-bin and other refuse deposited by the Norwich corporation 

 on the Whitlingham Marshes, at a distance of a little over 

 half-a-mile from the village church." In this mass of refuse 

 fermentation was actively going on, the fresher portions steaming 

 vigorously when the top layer was disturbed ; it was in fact an 

 almost ideal breeding ground for flies. Near this place was a 

 workmen's shelter, which was warm but ill-lit. " On cold days 



