178 INTERNAL ANATOMY OF INSECTS. 
der this head I may also observe, that the muscles are 
sometimes extremely slender threads, crossing each 
other, and often curiously interwoven in various direc- 
tions, so as to resemble lace or fine gauze, as may be 
seen in the alimentary canal of some caterpillars 3 ; some- 
times also they surround part of this organ, like a series 
of minute rings b . 
iv. Colour. The most usual colour of the muscles of 
insects is iv/iite : 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 
movements of any organs are effected, and the second- 
ary their auxiliaries which are the cause of subordinate 
movements d . 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 
remains without motion ; but when that of one prepon- 
derates, a movement in proportion takes place e . 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. Flexors that 
bend an organ, and Extensors that unbend or extend it. 
a Lyonet Anal. t. xiii./. 1, 2. 
b Ramdohr Anat. t. v.f. 1. c.f. 3. 
c Chabr. vbi supr. 440—. d Ibid. 442, &c. 
c N. Diet. cFHist. Nat. xxii. 80. 
