STATES OF INSECTS. (Larva.) 121 
which, applying close to each other, form a pair of power- 
ful grindstones, capable of comminuting the hardest tim- 
ber?*. M. Cuvier has observed, with regard to the man- 
dibulee of those of stag-beetles (Zwcanus), that besides 
their teeth at the extremity, they have towards their base 
a flat striated molary surface; so that they both cut and 
grind their ligneous food. It seéms to have escaped 
him, that a similar structure takes place in many perfect 
insects of the lamellicorn tribe, as I shall hereafter show 
you. In the larvee of the water-beetles (Dytzscus L.), 
ant-lions (Myrmeleon L.), and lace-winged flies (Zemero- 
bius L.), they resemble somewhat the forceps at the tail 
of an earwig, being long and incurved; and, what is more 
remarkable, hollow and perforated at the end, so as to 
serve as a channel for conveying into the larva’s mouth 
the juices of the prey which by their aid it has seized. 
Reaumur even asserts, that the larva of Myrmeleon has 
no other entrance into its throat than through these tu- 
bular mandibles:. That of the rove-beetles (Staphy- 
linus L.), and of many other Coleopterous genera, have 
these organs of this forcipate construction, without being 
perforated’. In the larva of the carnivorous flies, and 
many other Diptera, are two black incurved subulate 
parts, connected at the base, and capable of being pro- 
truded out of, and retracted into, the head, through the 
skin of which they are usually visible. As I informed 
you in a former letter *, these mandibles are used for 
walking as well as feeding : they are parallel to each 
other, and are neither formed for cutting nor grinding 
a Kirby in Linn. Trans. v. t. xii. f. 7. 0. 
> Cuvier Anat. Comp. iii. 322. © Reaum. vi. 340. 
4 The larva of Cicindela campestris has mandibles of this descrip- 
tion. Prater XVII. Fic. 13. c’. © See above, Vot, II. 275—. 
