072 



INSECTA. 



Fig. 428. 



Alimentary canal of Lwinua cema. . 



G, anterior muscles of the pharynx; H, (Eso- 

 phagus ; I, gizzard ; K, chylinc stomach ; L, ilium ; 

 M, colon (cojcal portion of); N, colon ; O, rectum ; 

 a, frontal ganglion on the vagus ; b, vagus ; c, an- 

 terior lateral ganglion connected to the vagus. 



longest. These are evidently analogous to the 

 vessels in Blutta. 



But one of the most remarkable forms of 

 alimentary canal with reference to the habits of 

 the insect exists in the male Litcanus cervus 

 (fig. 428), which subsists entirely upon fluid 

 aliment, as proved by the observations of natu- 

 ralists, and confirmed by the fact that its mouth 

 is unfitted for mastication. In this insect the 

 (esophagus (II) is usually long and narrow, and 

 terminates in the meso-thorax in a well deve- 

 loped gizzard (I), as in the Carabus, and this 

 is succeeded by a long chylinc stomach (K), 

 covered throughout its whole extent by very 

 minute rudimentary cceca, as first noticed by 

 Dufour. It makes three distinct convolutions, 

 and is then divided by a pylorus, which re- 

 ceives four hepatic vessels (P) from an ex- 



ceedingly short ilium (L), which passes directly 

 in an enormous colon. The upper portion of 

 this(M) is divided from the lower (N), which 

 is thus divided into colon and ccectim. It ter- 

 minates in a long folded rectum (N,O), and 

 the whole are usually filled with faces. Now 

 this insect, in which both gizzard and gastric 

 vessels are present, can scarcely require these 

 parts for the purpose of triturating its food, 

 which is entirely fluid, besides which, being 

 one of those species that undergo a complete 

 metamorphosis, it can scarcely be supposed to 

 be simply a remains of what existed in the 

 larva state. The presence of the gizzard may 

 be looked upon as somewhat anomalous. 

 Again it may be remarked, that in Ilymenoptera 

 the stomach, which in many species digests 

 only liquid concentrated food in the form of 

 honey, is much longer than in those instances, 

 as in Orthoptera, in which the food is less 

 easily digestible. In the Apidte there is a large 

 alimentary canal with an immense number of 

 biliary vessels attached to it, while in the 

 Tcnthredinidte, which, besides honey, subsist 

 partly upon the pollen of flowers, as we have 

 observed in Athtdia eentifotia, there is a very 

 short alimentary canal and even a distinct 

 gizzard (fig. 429, I), situated between the 



Fig. 429. 



Section of the crop (H), gizzard (I), and stomach 

 (K) of Alitalia centifoliee. (Newport, Prize Essay). 



stomach (K) and the dilated oesophagus (II) 

 or crop of this order. We have detected pollen 

 in the proventriculus of this insect, so that in 

 these we have still further proof that the length 

 of the canal is not always indicatory of the 

 habits of the species. 



In the Lepidoptera, which, we have seen, in 

 the larva state have a short intestine, have a com- 

 paratively long one in the perfect. In the 

 Sphinx ligustri (fig. 430), the oesophagus (/i) is 

 long and narrow, and in the metathoracic seg- 

 ment is dilated into a large crop (<) connected 

 by a distinct neck, but not divided from it by a 

 valve. This is usually filled with air, and has 

 thence been called the sucking ttomach, but in 

 the Diptera, in which it also exists, and com- 

 mencing much nearer the pharynx is extended 

 backwards as a long and gradually enlarging 

 tube until it reaches the anterior part of the 

 abdomen, where it is expanded transversely 

 into a large bag, we have certainly found it 

 partially filled with food. This has often been 

 found to be the case in the common flesh-fly. 

 In Erixtalisjloreus(l) we have found it partially 

 filled with yellow pollen from the flowers of 

 the ragwort, upon which the insect was cap- 

 tured. We have at the same time observed 



