INTERNAL ANATOMY OF INSECTS. 179 
a sengle pair of muscles that had their attachment in the 
coxa; and probably many other variations in this respect 
exist, , 
Little was known with respect to the most interesting 
part of the muscular apparatus of insects, that by which 
such wonderfully rapid and varied motions are imparted 
to their organs of flight, till Chabrier undertook to elu- 
cidate it; which he has done in a manner that will con- 
fer a lasting honour upon his name, as one of the most 
able successors to Swammerdam and Lyonnet in their 
peculiar department. He has given a most admirable 
account of the internal anatomy of the trunk of insects 
in general, as far as it relates to their flight; particularly 
of that of the cockchafer (Melolontha vulgaris), of one 
of the Libellulina (Aishna grandis), and of a humble-bee 
(Bombus); and I believe he has thus illustrated insects of 
some of the other Orders, but his memoirs on these I 
have not had an opportunity of consulting. What I 
have to say on this subject, therefore, will be principally 
derived from what he has communicated with respect to 
the above insects. 
A considerable difference in the volume of the muscles 
of the wings takes place in insects according to the force 
of their flight. Where it is rapid and powerful, the ali- 
trunk is nearly filled by them, and the alimentary canal 
is much attenuated; but in those whose flight is feeble, 
they occupy less space, and the alimentary canal is 
proportionally enlarged. In the Lepidoptera, Hy- 
menoptera, and Diptera, the principal muscles of both 
wings have their attachment in the anterior portion of 
the alitrunk®; in the Coleoptera, in the posterior*; and 
* Chabr. Sur le Vol des Ins. c. i. 441. & Thid, 415, Oe ial 
NZ 
