10 



THE INSECT WORLD. 



Fig. 10, which represents the digestive apparatus of Carabus 

 aurattts, a common beetle, presents to the eyes of the reader the 

 different organs of which we are speaking. 



A is the mouth of the insect, B the oesophagus, c the crop, D the 

 gizzard, E the chylific ventricle, F and G the 

 small and large intestines, and H the anus. 



It is not necessary to consider the other 

 parts of the alimentary canal in insects, but 

 only to refer to some of the appendages of 

 this apparatus. 



The salivary glands pour into the di- 

 gestive tube a liquid, generally colourless, 

 which, from the place where it is secreted, 

 and its alkaline nature, corresponds to the 

 saliva in vertebrate animals. It is this 

 liquid which comes from the tongue of 

 sucking insects in the form of drops. 



These glands are always two in number. 

 Their form is as variable as complicated. 

 The most simple is that of a closed flexible 

 tube, generally rolled into a ball, and open- 

 ing on the sides of the oesophagus. 



At the posterior extremity of the chylific 

 ventricle are inserted a variable number of 

 fine tubes, usually elongated and flexible, 

 and terminating in culs-dc-sac at one end. 

 Their colour, which depends on the liquid 

 they may contain, is sometimes white, but 

 more frequently brown, blackish, or green. 

 They appear to be composed of a very 

 slight and delicate membrane, as they are 

 very easily torn, and nothing is more diffi- 

 cult than to unroll and to disengage them 

 from the fatty or other tissues by which 

 they are enveloped. 



The function of these vessels is uncer- 

 tain. Cuvier and Leon Dufour supposed 

 them to be analogous to the liver, and on 

 that account they have been called biliary 

 vessels ; and they are often termed the Malpighian vessels, after the 

 name of their discoverer. 



According to M. Lacordaire, their functions vary with their 



Fig. ii. Posterior extremity of the 



chylific ventricle, surrounded by the 



Malpighian vessels. 



