HABITS 91 



Sunimary of feeding experiments, given in CJiaptcrs V, 

 VI and VII. 



Musca domestica feeds readily on various liquids such as 

 syrup, milk and sputum. Provided the food is supplied in the 

 form of well separated, discrete drops the flies do not usually 

 appear to soil their legs. When undisturbed the flies gorge 

 themselves in half a minute or less. The fluid first passes into 

 the crop, which becomes distended, and if the food is coloured 

 its contour can be seen through the ventral surface of the 

 abdomen. Under ordinary conditions the fluid begins to pass 

 into the ventriculus within 10 minutes and in two or three hours 

 coloured material can be found throughout the intestine. At 

 high temperatures it passes more rapidly. The crop, however, 

 is not completely emptied for many hours. Sometimes flies go 

 on feeding after the crop is full and then the food passes directly 

 into the ventriculus and intestine. If flies are allowed constant 

 access to food coloured material from the first meal remains in 

 the crop for many days. 



The crop therefore seems to act as a large receptacle which 

 can be filled with great rapidity so that flies can obtain within a 

 few seconds sufficient nourishment to keep them alive for several 

 days. When food is abundant the crop acts as a reservoir in 

 which surplus food is stored for use if necessity arises. 



After feeding on liquid food flies habitually exude drops 

 of fluid from their proboscides. Sometimes these drops are 

 sucked up again and sometimes deposited on the surface on 

 which the flies are walking. These deposits, which have been 

 spoken of as ' vomit,' dry and produce round marks with an 

 opaque centre and rim and an intervening less opaque area. 



If allowed to feed on half dried materials the flies first 

 moisten with vomit or saliva a small area and then suck it dry. 

 In so doing they usually leave oval depressions, often exhibiting 

 most beautifully the markings on the proboscis, or clear areas. 

 If the flies have previously fed on coloured syrup these proboscis 

 marks often show traces of pigment. 



When feeding on sugar small areas are moistened, either with 

 saliva or, in the case of flies fed on fluids, with vomit. Traces 



