Thorax in winged Insects. 157 
sects, particularly of the analogous orders Hymenoptera and Diptera. 
But a little study of their structures will point out the nature of such 
aberrations, and I repeat that the above is the most correct mode of view- 
ing an insect. Even coleopterous Annulosa, such as a Curculio or Ce- 
rambyx, * may be reduced to the same law of structure, the posterior 
abdominal segments of their larve being converted more or less into 
parts of the organs of generation. One of the most beautiful facts that 
the study of comparative anatomy presents us with, is the delight Nature 
appears to take in working as it were with a given quantity of material, 
while she nevertheless produces an infinite variety of forms. 
The developement of the various segments of the body of annulose 
animals forms another consideration, and a most important one. If the 
developement of each segment be tolerably uniform, we have the great 
majority of worms and larve. If, on the contrary, the developement of 
the thirteen segments be irregular, we have the majority of perfect insects, 
Arachnida, and Crustacea. In general we may add, that if any one of 
the three principal parts of the body be greatly developed, the general 
size being given by the full grown larva, then one or both of the remain- 
ing parts must be proportionably small in the perfect insect. This in- 
deed clearly amounts to a truism: and therefore, taking the size of the 
larva as a limit, we cannot be surprised that the head and abdomen of an 
Evania, for instance, are so small when the developement of its thorax is 
so great. 
The object of my present investigation shall be the thorax + of a winged 
insect. It is here that M. Audouin has particularly distinguished himself 
* I have not alluded in the text to Mr. Kirby’s tables, given pp. 703 and 704 
of his third volume, or to his previous description of the abdomen in insects, 
because in some cases they are founded on imperfect examination, and in others 
on that deficiency of generalization which I cannot help thinking the learned 
author was solicitous should characterize his work. 
+ Fabriciusin his “Philosophia Entomologica’ has called this part the truncus, 
an expression which implies the whole body without the head and limbs. Being 
thus objectionable, the term seems never very generally to have come into use; 
and in fact becomes quite unnecessary if we divide the thoraw into prothoraz, 
mesothorax, and metathoraxz, M. Audouin, therefore, has discarded it as use- 
less as well as objectionable. See Ann. des Sciences Naturelles, Vol. 1. p. 119. 
