INTERNAL ANATOMY OF INSECTS. 15 
of mandibles and palpi in the great Hydrophilus* ; and 
in Blatta some which act also upon the antenne?. 
The optic are usually the most conspicuous and re- 
markable of the nerves. In some insects with large eyes, 
as many Neuroptera, Hymenoptera, and Diptera, their 
size is considerable; in the hive-bee they present the ap- 
pearance of a pair of kidney-shaped lobes, larger than 
the brain®; in the dragon-flies, whose brain consists of 
two very minute lobes, these nerves dilate into two large 
plates of a similar shape, which line all the inner surface 
of the eyes‘; in the stag-beetle they are pear-shaped, and 
terminate in a bulb, from which issue an infinity of mi- 
nute nerves®; it is probable that this takes place in all 
cases, and that a separate nerve renders to every separate 
lens in a compound eye‘; the optic nerve in Dytiscus and 
Carabus is pyramidal, with the base of the pyramid at the 
eye and the summit at the brain’; in Elophilus tenax 
it is very large, cylindrical, and of a diameter equal to 
the length of the last-mentioned part, upon the side of 
which it is supported; it terminates in a very large bulb 
corresponding to the eye"; in Scolopendra morsitans the 
optic nerves divide into four branches long before they 
arrive at the eyes, and in this insect the nerves which 
render to the antennee are so thick as to appear portions 
of the brain, which they equal in diameter'. Swammer- 
dam discovered in the grub of the rhinoceros-beetle and 
in the caterpillar of the silk-worm, a pair of nerves which 
- * Cuy. Anat. Comp. ii. 339. b [bid. 342. 
¢ Swamm. Bid. Nat. t. xxii. f. 6. m.m. 
4 Cuv. wi supr. 350. ° Ibid. 335. 
f Vor. III. p. 497. Lyonnet Anat. 581. | 
® Cuv, uli supr. 337. h Tbid, 301. ' Thid, 352. 
