432 EXTERNAL ANATOMY OF INSECTS. 
custa), they are extremely thick and powerful organs, and 
fitted for their work of devastation; but in the glow- 
worm (Lampyris), they aretvery slender and minute. 
In those brilliant beetles, the Buprestes, they are very 
short; but in the stag-beetles, and those giants in the 
Capricorn tribe, the Prioni, they are often very long?. 
They either meet at the summit, lap over each other, 
cross each other, or are protended straight from the 
head; as you have doubtless observed in the stag-beetle, 
whose terrific horns are mandibles of this description. 
These organs are usually symmetrical, but in some in- 
stances they are not: thus in Hister levus, a kind of 
dung-beetle, the left-hand mandible is longer than the 
right; in Creophilus mazillosus, a common rove-beetle, 
in the left-hand mandible the tooth in the middle is 
bifid, and in the right-hand one intire; and in Bolbo- 
cerus the mandible of one side, in some species the dex- 
ter, and in others the sinister, has two teeth, and the 
other none. 
The next circumstance with respect to these organs 
which demands our attention, is the teeth with which 
they are armed. These are merely processes of the 
substance of the mandible, and not planted in it by gom- 
phosis», as anatomists speak, as they are in vertebrate 
animals. They have, however, in their interior, at the 
base at least, in the Orthoptera, a coriaceous lamina that 
separates them in some sort from the body of the man- 
* For Mandibles of Locusta see Piate VI. Fic. 6. c’. of Lampyris, 
Oliv. Ins. no. 28. t. i. f. i. of Buprestis, Ibid. no. 32. t. ili. f. 17. of 
Lucanus, Ibid. no. |. t.i—v. and of Prionus, Ibid. no. 66. t. ii. f.8. 
> Gomphosis is, when one bone is immoveably fixed in another as 
a nail in a board, 
