INTERNAL ANATOMY OF INSECTS. 107 15 
der this head I may also observe, that the muscles are 
sometimes extremely slender threads, crossing each other, 
and often curiously interwoven in various directions, so 
as to resemble lace or fine gauze, as may be seen in the 
alimentary canal of some caterpillars? ; sometimes also 
they surround part of this organ, like a series of minute 
rings>. 
iv. Colour. The most usual colour of the muscles of 
isects is white: those for flight however, according to 
Chabrier, differ from the rest, by being of a deeper and 
reddish colour® ; and I have observed likewise that those 
in the head of the stag-beetle, when dried at least, are 
red, and look something like the flesh of warm-blooded 
animals. 
v. Kinds and Denomination. In general, muscles may 
be regarded as divided into primary and secondary—the 
primary being the muscles by which the principal move- 
‘ ments of any organs are effected, and the secondary their 
auxiliaries which are the cause of subordinate move- 
ments’. Every muscle almost has its antagonist, the 
action of which is in an opposite direction; so that when 
it is equal, the organ to which they are attached re- 
mains without motion; but when that of one prepon- 
derates, a movement in proportion takes place®. The 
principal antagonist muscles that may be found in insects 
are the following. 1. Levator muscles that raise an or- 
gan, and Depressors that depress it. 2. Hlexors that 
bend an organ, and Eztensors that unbend or extend it. 
a Lyonnet Anat. t. xiii. f. 1, 2. 
b Ramdohr Anat. t. v. f. lo e. f. 3. 
* Chabr. ubi supr. 440—. * Ibid. 442, &c. 
© N, Dict. d’ Hist. Nat. xxii. 89. 
