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ANATOMY AND PHYSIOLOGY 
which we cannot here afford room to enumerate and 
characterise. As the parts in question exercise pre- 
cisely the same functions as among the higher animals, 
the same terms are applied to them, and they are 
spoken of as flexor, extensor, abductor, adductor, 
rotatory muscles, &c. appellations which scarcely re- 
quire any definition. We shall mention a few of the 
principal ones in the different parts of the body. 
Muscles of the Head . — The head having freer motion 
than any other part, except the pedunculated abdomen 
of aculeate species, is furnished with a corresponding 
provision of muscles. Those which move the whole 
head, when that part is sunk in the prothorax, for the 
most part consist of four pairs, besides three other 
subsidiary pairs which contribute more or less directly 
to aid their movements. When the head is pedun- 
culated, the muscles are very small and rudimentary. 
Of those which produce the motions of the oral organs, 
a pair only are appropriated to the mandibles ; the 
maxillae, being composed of a greater number of pieces, 
and bearing the palpi, have each nine attached to 
them ; the palpi have each a pair, and every separate 
joint is similarly provided. A single muscle, or at 
most two, suffice for the limited motions of the labrum, 
but its counterpart, the labium, whose action is more 
frequent and extensive, is furnished with four, besides 
those appropriated to the palpi. The motive apparatus 
of the antennae consists of three general muscles for 
each, and two others, an extensor and flexor, for every 
individual joint. Besides these, several muscles are 
to be found in the vicinity of the pharynx, whose office 
