INTERNAL ANATOMY OF INSECTS. 125 



but in some species it is yellowish, or reddish, and its 

 lower surface has sometimes regular excavations a ; no 

 transverse hepatic ducts connecting it with the alimentary 

 canal, as in the scorpion, appear to have been at present 

 discovered : two pairs of capillary free vessels are at- 

 tached to the base of the rectum on one side, which, ex- 

 cept in their situation, seem analogous to the bile-vessels 

 of insects b . 



From the above detailed account of the alimentary 

 canal of the animals whose internal anatomy we are con- 

 sidering, it appears 'that M. Cuvier's observation that 

 the length and complication of the intestines indicate a 

 less substantial kind of nutriment does not hold univer- 

 sally: thus, in Necrophorus andSilpha, carnivorous insects, 

 the intestinal canal in its length and convolutions exceeds 

 those of most herbivorous ones, and in Cassida viridis and 

 some others of the latter tribe are not longer than those 

 of the predaceous beetles. In herbivorous larvce also, in 

 general, the length of the alimentary canal does not ex- 

 ceed that of the body, but in those of some jlesk-Q.ies 

 (Musca vomitoria) it very greatly exceeds it c . So true 

 is the observation that there is no general rule without 

 exceptions. 



In this letter it may not be out of place to say a few 

 words upon the excrements of insects ; which, strange as 

 the observation may seem, but it is no less true than 

 strange, are sometimes pleasing to the eye, from their 

 symmetry, and to the taste, from their sweetness. In 

 those that masticate their food they are solid, and in 

 those that take it by suction, fluid or semi-fluid. In the 



a Treviran. Ibid. 28. b Ibid, t ii./. 24. /3. 



c Ramdohr, t. xix.jT. 1. 



