78 



THE HABITS AND BIONOMICS OF THE HOUSE-FLY 



the crop rapidl}'. The fly then rests in a quiet place. The 

 absorbed food now begins to flow through the proventriculus, 

 which acts as a pump and valve, into the ventriculns'. I have 

 compared this to the feeding of the ruminating animal, as the crop 

 of the fly calls to mind the storage stomach of the ruminant. 



Fig. 33. Proboscis marks of a fly (not 31. domeatica) allowed to feed on film of 

 Indian ink (sweetened) ; showing the alternating light and dark lines, the 

 former being where the film has been removed by the pseudo-tracheae. Greatly 

 enlarged. (Photogi-aphed by H. T. Giissow.) 



Graham-Smith found that the rate at which food passes into 

 the intestine from the crop appears to vary, depending to some 

 extent on the nature of the food and the temperature. If flies 

 were kept in an incubator at 57" C. and fed on carmine gelatine 

 much of the food may reach the rectal valve within one hour 

 of feeding. He gives the following tables which indicate the rate 



' Wheeler (1910) mentions the fact that in ants the proventriculus not only 

 passes the liquid food back fror.i the crop to the stomach but also fills the crop in 

 the first place. 



