DIGESTIVE ORGANS OF INSECTS. 



153 



To engage in a minute description of the endless varia- 

 tions In the structure of the digestive organs, presented in 

 the innumerable tribes which compose this class of animals, 

 would be incompatible with the limits of this treatise. T 



shall content myself, therefore, with 

 giving a few illustrations of their prin- 

 cipal varieties, selected from those in 

 which the leading characters of struc- 

 ture are most strongly marked. I shall, 

 with this view, exhibit first one of the 

 simplest forms of the alimentary or- 

 gans, as they occur in the Mantis reli- 

 giosa, (Linn.) which is a purely carni- 

 vorous insect, belonging to the order of 

 Orthoptera. Fig 317 represents those 

 of this insect, freed from their attach- 

 ments, and separated from the body. 

 The whole canal, as is seen, is perfect- 

 ly straight: it commences by an oeso- 

 phagus (o,) of great length, which is 

 succeeded by a gizzard (g;) at the low- 

 er extremity of this organ the upper 

 hepatic vessels (b, b,) eight in number, 

 and of considerable diameter, are in- 

 serted: then follows a portion of the canal (d,) which may 

 be regarded either as a digesting stomach, or a chyliferous 

 duodenum: farther downwards, the second set of hepatic 

 vessels (h h,) which are very numerous, but as slender as 

 hairs, are received: and after a small contraction (n) there 

 is again a slight dilatation of the tube (c) before it termi- 

 nates. 



has been repeated by every succeeding- anatomist; that almost all tlie insects 

 belong-ing" to the tribe of Grylll, possessed the faculty of ruminating- tiieir 

 food; but this error has been refuted by Marcel des Serres, wlio luis offered 

 satisfactory evidence that in no insect is the food subjected to a true rumina- 

 tion, or second mastication, by the organs of the mouth. See Annales du Mu- 

 seum, XX. 51 and 364. 



Vol. II. 20 



