INSECTA. 219 



distension. The bees on which Hunter experimented* endured a 

 long confinement, but could not be compelled to foul their hive ; as 

 soon as liberated, they rose in the air and disburthened their over- 

 laden cloaca. 



In the Lepidoptera i^fig' 105.), the ingluvies projects, like a bag, 

 from the side of the oesophagus {j) ; and in the Zygcence. it is divided, 

 as in the pigeon, into two equal parts. The chylific stomach is very 

 small, but is sacculated, and, according to Meckel, is shaggy in the 

 death's-head moth. The small intestine (/) is longer and more con- 

 voluted than in the bee ; the large gut (m) is short and wide. 



In the Diptera the cropf, though situated upon the stomach in 

 the abdomen, is appended by a long and slender neck to the be- 

 ginning of the narrow oesophagus. The lower end of the oesophagus 

 expands into the chylific stomach, the cardia being sometimes marked 

 by a callous ring, which is the remnant of a small bladder existing there 

 in the larva. The small intestine is convoluted ; the rectum short 

 and dilated, and provided with two lateral conical glandular bodies. \ 

 Hunter made experiments to determine the function of the appen- 

 diculated crop. " I kept a fly," he says, " for twelve hours without 

 food, and then gave it milk and killed it, and found no milk in the 

 crop, but it had got through almost the whole tract of intestines : 

 here the animal had immediate occasion for food, therefore the milk 

 did not go into the crop. This experiment at the same time shows 

 that every part of the intestine digests." Another time Hunter killed 

 his flies after they had drunk their fill, and found the crop full, as 

 well as the stomach and intestines : he suspects, therefore, that the 

 crop serves as a reservoir, and " that when there is more food than 

 what is immediately necessary, then it is thrown into the crop to be 

 used in future." § 



The result of Hunter's first experiment, and the absence of the 

 crop in the flea and some other suctorial insects, negative the idea of 

 Burmeister that the crop in Hymenoptera, Lepidoptera, and Diptera 

 promotes the suction of food by a voluntary power of self-expansion, 

 if even the structure of the part justified the idea ; but, on the con- 

 trary, they prove it to be a receptacle of nutriment. 



In the Cicadae the chylific stomach is of great length, intestiniform, 

 and its termination is connected, but does not communicate, with its 

 commencement ; the chymified fluids pass at once from its termi- 

 nation into the intestine. 



The entire alimentary canal consists of three tunics, an external 



* See Philos. Trans. 1792. p. 176. 



t No. 596. \ No. 2123. 



§ Physiol. Catalogue of Hunterian Collection, vol. i. p. 1 89. 



