90 HABITS 



milk. When all had fed they were transferred to a fresh cage. 

 At intervals the flies were again transferred to other fresh cages 

 and the deposits in the old cages counted. In the second series 

 (B) the deposits of 1 1 flies were counted in the same way, but 

 milk was always present in the cage so that the flies could feed 

 as often as they wished. 



TABLE 7. To illustrate the number of deposits left by flies. 



"Each fly in series (A) produced an average of i6"4 'spots,' 

 and in series (B) of 20"4. In another experiment 10 flies which 

 had been given one feed of milk, produced in nine hours 209 

 (191 vomit and 18 faeces) deposits, and in the complete 24 hours 

 307 (282 vomit and 25 feeces) deposits or an average of 307 

 ' spots ' per fly. 



" No doubt the rate at which flies produce deposits depends 

 on several factors, such as the temperature and the form of food, 

 etc., but only a few experiments on this subject were made. 

 Elies are more lively in hot weather or when placed in a warm 

 incubator. That the kind of food exerts a considerable influence 

 is shown by the following experiment. Three lots of flies were 

 fed on syrup, milk and sputum respectively for several days. 

 Those fed on syrup produced an average of 47 deposits per fly 

 per day, those fed on milk 8'3 and those fed on sputum 27*0. 

 In the latter case the faeces were much more voluminous and 

 liquid than usual and in fact the flies seemed to suffer from 

 diarrhoea." (Graham-Smith, 1910.) 



