]22 ANATOMY 



98. 



The length of the intestinal canal increases with its convolutions ; or 

 these rather are but the consequences of its extension. We very fre- 

 quently find the intestinal canal twice the length of the body ; indeed so 

 often is this the case that it may be considered as the most usual struc- 

 ture. A nutrimental canal of this extent is called MODERATELY long; 

 such an intestine makes from one to three convolutions, according to 

 their size. The LONG intestine (Chrysomela, Cimcx) makes also two 

 or three, but larger convolutions, and is from three to five times the 

 length of the body. The intestine is, lastly, very long in the Lamelli- 

 cornia, in which it is from seven to eight times as long as the body, 

 and makes many folds in the cavity of the abdomen. 



But these proportions refer only to the perfect insect, for the majority 

 of larvae, namely those with a perfect metamorphosis, have a nutri- 

 mental canal of the same length, or at most of twice the length of the 

 body. This short intestine increases in length in every distinct period 

 of its life ; but some instances occur in which this gut becomes shorter 

 during the metamorphoses, namely, in the Diptera, the larvae of which 

 have a very long and much convoluted intestine *. 



99. 



No general law regulating the various length of the intestinal canal 

 has yet been discovered ; in insects, in particular, it appears exposed 

 to much irregularity. It is not however improbable, from all hitherto 

 instituted investigations, that herbivorous insects have a longer and 

 more distended intestine, and that those which feed upon animal 

 matter have it shorter and narrower. We, however, find a decided 

 exception in the vegetable devouring Orthoptera (e. g. Gryllus, Lo- 

 custa), their intestine being not much longer than their body, but at 

 the same time very broad. We perceive greater uniformity, if not in 

 length yet in structure, in the different orders of insects, and this law 

 we shall observe to prevail still more forcibly in the still smaller groups. 



100. 



We will now pass from this general description of the entire intes- 

 tinal canal to the examination of its different divisions. We can there- 



* Ranidohr, PI. XIX. f. 1 and 2. 



