EXTERNAL ANATOMY OF INSECTS. 4.39 
less liable to variation than almost any other organ, as 
Mr. W. S. MacLeay has judiciously observed, there 
seems good reason for employing them—it is therefore 
of importance that you should be well acquainted with 
them. 
Their situation is usually below each mandible, on each 
side of the Jabiwm ; towards which they are often some- 
what inclined, so that their tips meet when closed. In 
some cases, as in the Predaceous beetles, they exactly 
correspond with the mandibles; but in others their di- 
rection with respect to the head is more longitudinal, as 
in the Hymenoptera, &c. In substance they may be ge- 
nerally stated to be less hard than those organs; yet in 
some instances, as in the Libellulina, Anoplognathide, &c. 
they vie with them, and in the Scarabeide and Cetoni- 
ade exceed them, in hardness., In the bees, and many 
other Hymenoptera, they are soft and leathery. Their 
articulation is usually hy means of the ‘hinge on which 
they sit: it appears entirely ligamentous, and they are 
probably attached to the labzum at the base, or mentum— 
at least this is evidently the case with the Hymenoptera, 
in which the opening of the mazille pushes forth the 
labium and its apparatus. In that remarkable genus re- 
lated to the glow-worms, now called Phengodes, and in 
the case-worm flies ( Trichoptera), the maxilla appear to 
be connate with the /abium, or at least at their base.— 
As to their composition, these organs consist of several 
pieces or portions. At their base they articulate with a 
piece more or less triangular, which I call the hinge 
(Cardo)*. ‘This on its inner side is often elongated to- 
wards the interior of the base of the labéwm, to which it 
Pras Visbie. 3, 6, 1%. 2Vil: Fie. vel’ 
