SIGNIFICANCE OF FEEDING HABITS 75 



feeding habits of the fly essential to a thorough comprehension of 

 the possibilities of bacterial disseminati<jn by flies. This problem 

 will be fully discussed later when it will be shown that the trans- 

 portation of bacterial and other organisms in the alimentary tract 

 is of greater import than the transportation of such organisms 

 externally, on the legs, proboscis, etc., of the fly. 



Most people are acquainted in a general way with the feeding 

 habits of the house-fly. Its visits to the dining table are a matter 

 of common kn<iwledge ; the general ignorance in regard to its 

 visits to repositories of filth and excrementous matter has been 

 largely responsible for the indifference of the majority of people to 

 the hygienic aspect of the house-fly. 



The anatomy of the proboscis and of the alimentary tract, a 

 knowledge of which is essential to understanding the feeding 

 habits of the fly, have already been described. Although I made 

 extended observations on the feeding habits of the house-fly from 

 the beginning of my study of this insect, these observations 

 were not recorded in my earlier papers and to Graham-Smith 

 belongs the credit of first rec(jrding any extensive and accurate 

 observations on this subject. In his papers (1910, 1911a and 

 1911 &) he has given an excellent account of the general behaviour 

 of flies during feeding and of the digestion of the food and his 

 observations fully confirm those which I had made ; he also makes 

 a large number of new observations in connection \^dth his bacterio- 

 logical studies and his study of the structure and function of the 

 oral sucker of the blow-fly is invaluable. 



The proboscis of the house-fly is adapted to a sucking function 

 and the absorption of liquid or liquefied food. Except under certain 

 circumstances it does not and caiuiot take in solid particles of food. 

 Nicoll (1911) in his experiments on feeding flies on the eggs of 

 tapeworms found that flies were "apparently unable to ingest 

 particles of larger size than '045 mm." A careful examination of 

 the structure of the oral lobes or sucker makes plain the reason for 

 this. As I have sho^\^l in describing the structure of the oral 

 lobes, and as Graham-Smith in his study of the oral sucker of the 

 blow-fly also pointed out, communication between the surface of 

 the oral lobes and the pseudo-tracheal channels is effected by w^ay 

 of the spaces between the bifid extremities of the chitinous rings 



