FUNCTION OF CROP 73 



" The rate at which the food passes from the crop into the 

 intestine appears to vary, depending to some extent on the 

 temperature and the nature of the food. For example, if the 

 flies are kept in the incubator at ''^'j° C. and fed on carmine 

 gelatin much of the food may reach the rectal valve within an 

 hour. 



" If the flies are disturbed before the crop is completely 

 distended the contents of the crop are gradually passed into the 

 intestine, but the organ is not completely emptied for many 

 hours, or in some cases for days, even though no further food is 

 given. In most examples which were dissected the crop was 

 found nearly empty on the third day after feeding, but the 

 intestine still contained large quantities of red material. 



"Flies allowed to feed to their utmost capacity on carmine 

 syrup showed a red colour all over the ventral surface of the 

 abdomen within an hour or two, and dissections showed that 

 the crop and intestine, down to the anus, were distended with 

 coloured syrup. If such flies are subsequently fed on plain 

 syrup it is found that most of the red material from the first 

 meal is retained in the crop and only slowly passed into the 

 intestine. Dissections show that a considerable quantity of the 

 carmine, though diluted, is still present in the crop, under such 

 conditions, after several days. For example a number of flies 

 were fed once on carmine syrup, and were subsequently given 

 plain syrup daily. 



TABLE 4. Showing the period during tvhich coloured food 

 may rcmaiii in the crop. 



Time after feeding ,-' , , Result 



24 hours ... ... 2 Crop red and distended. Intestine red 



throughout. 

 48 ,, ... ... 3 Crop red and distended. Intestine red 



throughout. 



3 days ... ... 3 Crop red and distended. Intestine red 



throughout. 



4 ,, ... ... 1 Crop pink and distended. Intestine red 



throughout. 



" From these experiments, of which a large number were 

 performed at different times, it appears that in these insects the 



