INTERNAL ANATOMY OF INSECTS. 119 
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 and Silpha, 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 Jatter tribe are not longer than those 
of the predaceous beetles. In herbivorous larve also, in 
general, the length of the alimentary canal does not ex- 
ceed that of the body, but in those of some jlesh-flies 
(Musca vomitoria) it very greatly exceeds it?. 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 
caterpillars of Lepzdoptera they are of the former de- 
scription, and every grain wears some resemblance to an 
insect’s egg: as the passage in many of these consists of 
six fleshy parts separated by channels, so the excrement 
represents six little prisms separated by six channels». 
The Aphides all secrete a fluid excrement as sweet as 
honey, of which the ants are so fond‘, which is ejected 
not only at the anal passage, but, in many, by two little 
* Ramdohr, ¢. xix. f. 1. > Reaum, i. 143 t. v.f. 9. 
© Vor. II. p. 88—. 
