RATE OF PASSAGE OF FOOD 



79 



at which the food passes from the crop and llif jn'iiod dining 

 which coloured food may remain in the crop. 



TABLE SHOWING THE RATE AT WHICH FOOD PASSES THROUGH 

 THE CROP INTO THE INTESTINE. 



(from Graham-Smith.) 



Time after 1 Number of 

 feeding flies dissected 



Results 



TABLE SHOWING THE PERIOD DURING WHICH COLOURED 

 FOOD MAY REMAIN IN THE CROP. 



(from Graham-Smith.) 



In most cases on dissection the crop was found to be nearly 

 empt}^ on the third day after feeding, although the intestine still 

 contained large quantities of red material. The above results indi- 

 cate that the crop is not completely emptied for many hours and 

 in some cases for days, even though no further food is given. This 

 fact has been confirmed in my own observations. Flies which have 



