26 ALIMENTARY ORGANS. 



undoubtedly one of the most interesting branches of 

 entomology, we must pass it over in a very few words, 

 as it has but little practical bearing upon the classifi- 

 cation of Insects. A brief reference to some of the 

 leading points in the internal structure of these crea- 

 tures, is however necessary for the completion of the 

 subject, especially as it will show that even in the 

 smallest of these living atoms the phenomena of life 

 are produced by a complex apparatus, scarcely, if at 

 all, inferior to that by which the functions of animals 

 far higher in the scale of existence are performed. 



The first set of organs to which we must turn our 

 attention is the alimentary canal with its appendages, 

 for since the days when the quaint old fable of the 

 belly and the members stilled the angry populace of 

 Ancient Rome, there has never been any doubt of the 

 primary importance of the alimentary organs in the 

 animal oeconomy. In Insects, as in most other animals, 

 the alimentary canal forms a membranous tube, which 

 runs through the whole length of the body from the 

 mouth to the anal opening. It is composed of three 

 membranes, of which the innermost is a continuation 

 of the external skin, whilst the outermost is a muscu- 

 lar layer, which appears to contract with great force. 

 In different parts of its course, this tube expands into 

 two or three bags or stomachs, which exhibit consider- 

 able differences in their internal structure, and serve 

 different offices. Of the tubular portions, the first is 

 the oesophagus or gullet, which leads from the mouth 

 into the thorax, and sometimes, in those insects whose 

 abdomen is attached to the thorax by a very narrow base, 

 passes quite through the latter. This usually conveys 

 the food into a folded stomach called the crop, from 

 its analogy with that organ in birds, and immediately 



