tlfSECTA. 



oog 



Stimmeri, and as seen by ourselves in CaUidium 

 luriiliim. In Ctttandra, winch in external ap- 

 ]>earaiif:c is searcely more pertirt th.m tlii; 

 ii]nnlal larva of liymenoptera, the alimentary 

 cana ' (f'S- 427 ) approaches much in form, 



Fig. 427. 



A limentary canal of the 



lnr>'a of Ciitttit'lrn Sutn- 

 meri. (Burmeuter. ) 



si/e, and complication of its parts to that of 

 the perfect insect. It commences behind the 

 pharynx in a very short pear-shaped oesopha- 

 gus (II), which opens by a valve into a dilated 

 bag-shaped crop (I), analogous probably to 

 the first stomach of the larva of Calosomn. This 

 is continuous by a narrowed passage with the 

 proper digestive cavity, around the middle part 

 of which (K) are developed many conical glan- 

 dular papillae or gastric vessels, that do not 

 apjxiar to have been noticed in the larva of 

 Ciilnsi'Hia, which instead of subsisting upon 

 hard vegetable substances like these Cnrrii/io- 

 nidtr, preys upon the soft bodies of living cater- 

 pillars, and consequently does not require for 

 the digestion of its soft animal food and juices 

 so complicated a structure as those which de- 

 vour large quantities of crude vegetable matter, 

 as is the habit of the IJIIIH //ironies, or the hard 

 and less easily solvent woody fibre or coverings 

 of insects devoured by the t'tilandra or the 

 perfect Carabitltc. At the posterior extremity 

 of the digestive stomach in this larva are in- 

 serted, as before seen, tlie biliary vessels, not 

 singly around the sides of the canal, but by 



the union of four of these tubes in a common 

 duct. Tins pe.ulianty is remarkable, as it 

 occurs in some species in the perfect in- 

 sect. Upsides U,'se vessels there are two 

 others somewhat smaller, which are inserted 

 separately, a little anterior to the common duct. 

 These have been supposed to be analogous 

 to pancreatic vessels, but they arc .smnl.tr 

 in almost every respect to those which are 

 inserted by a common duct, and hence may 

 be sup|x>sed to have nearly the same functions. 

 We have noticed similar vessels inserted sepa- 

 rately from the supposed hepatic vessels in the 

 Vi/ticida and in Timarclia, which certainly 

 leads to the conclusion that they have some 

 difference of function. The ilium (L) is of 

 great length, and more convoluted than we 

 have yet seen it in any larva, and ends in a very 

 muscular cylindrical colon (M N), terminated 

 by a short rectum. A similar and perhaps 

 even more highly developed form of alimentary 

 canal exists in Callidum luridum, in which the 

 anterior portion of the oesophagus commences 

 with a small neck, and is then enormously di- 

 lated, after which it becomes gradually narrowed 

 and constricted, and is joined to a second sto- 

 mach, which in like manner is also dilated at 

 its anterior extremity. In the middle part of 

 its course it is twice folded, and is covered with 

 minute caeca, as in Calandra, like which it ter- 

 minates in a valvular pylorus, and receives at 

 the same time the insertions of the hepatic ves- 

 sels. The ilium' is also of considerable length, 

 is exceedingly muscular, and is dilated in two 

 parts of its course before it terminates in a 

 straight and very muscular colon and short 

 rectum, as in Calandra. The length and com- 

 plication of the intestines, therefore, appear to 

 nave some reference to the quality of (he food 

 to be digested, since it is well known that the 

 food of these latter insects is of difficult assi- 

 milation, being as it is chiefly the hard ligneous 

 fibres of vegetable matter; but they cannot be 

 received as always indicatory of a carnivorous 

 vegetable feeder, since, as above remarked, the 

 length of the canal is considerable in one en- 

 tirely carnivorous larva, while it is much shorter 

 in some herbivorous, and particularly in polleni- 

 Torous larva>, as in the Melolont/ia and the 

 apodal Hymenoptera. 



In the perfect insect, the length of the ali- 

 mentary canal is not more indicatory of the ha- 

 bits of the species than in the larva. It is 

 nearly as long, and is more complicated, in the 

 rapacious Carabide (fig. 423) than in the 

 honey-sipping Lepidoptera, whose food is en- 

 tirely liquid, while, as we have seen, it is only 

 a very short tube in the pollenivorous larva, 

 which subsists upon a mixture of pollen and 

 honey ; but in the perfect insect, which subsists 

 upon honey alone, and which it might be sup- 

 posed requires little power of digestion, the 

 canal is long and tortuous. In the rapacious 

 Carabidte, it is from two to three times the; 

 length of the whole body. At its commence- 

 ment at the pharynx it is funnel-shaped, and 

 opens directly into the oesophagus (Jig. 424, A'), 

 which is gradually enlarged as it passes through 

 the thorax, until it arrives at the meta-thor.inr 

 segment, where it becomes greatly dilated, and 



