THE ORGANS OF NUTRITION. 129 



cular ridges. The cardia itself was armed with six Y-shaped horny 

 teeth (PI. XXI. f. 6. a, a). In Muller's representation of the intes- 

 tinal canal of Phasma no proventriculus is visible *, I consequently 

 surmise they would present a similar structure. 



The exterior skin of this organ is tense, not folded, and it closely 

 incloses the interior one as a similarly shaped distended bag. It agrees 

 in structure with the muscular membrane of the intestinal canal. 

 The space between both is occupied by fasciculi of muscles, and the 

 spongy layer or middle membrane must necessarily be deficient here as 

 well as in the crop, it being the produce of digestion, and therefore can 

 only be present where this has commenced. 



The larvae of all the above-named insects whose metamorphosis is 

 complete, entirely want this organ, and in them the pharynx passes 

 immediately into the considerably wider stomach. We do not either 

 observe in the very voracious caterpillars of the Lepidoptera any further 

 comminuting stomach. 



105. 



THE STOMACH. 



The stomach (ventriculus, PI. XVII. XXII. D, D), according to 

 most entomologists, is that portion of the intestinal canal which extends 

 from the end of the oesophagus, or of the crop, to the opening of the eva- 

 cuating ducts of the biliary vessels. Straus, Treviranus, and Joh. 

 Miiller -f- call it the duodenum, as digestion commences in it, in those 

 orders which have the proventriculus, and perhaps this interpretation 

 may be more correct than that hitherto used. 



Upon examining the form of this portion of the intestine it soon 

 becomes apparent that it is subject to many changes ; it always 

 approaches more or less to the tubular, but it at the same time distin- 

 guishes itself from the following divisions of the canal by its greater 

 compass. The shorter the stomach is the further does it recede from 

 the tubular form, and approaches to the ovate, conical, or bladder- 

 shaped. 



The Lepidoptera (PI. XVIII. f. 5. D) have the smallest stomachs 

 of all insects. In these it takes the shape of an egg, the ends of which 

 contract into narrow tubes, and its upper surface is folded in irregular 



* Nova acta Phys. Mecl. n. cur. T. 12. B. PI. L. f. 2. 

 f Job. Miiller de Glandul. Secern. Struct. Pen. p. 68. Lips. 1831, fol. 



K 



