502 EXTERNAL ANATOMY OF INSECTS. 
eyes under a lens, and you will be astonished at the bril- 
liance and crystalline transparency which its large eyes 
exhibit, and by the remarkable vision of larger hexagons 
which appear in motion under the cornea, being reflect- 
ed by the retina—all which give it the appearance of a 
living eye. This moving reflexion of the hexagonal 
lenses in living insects was noticed long since in some 
bees (Nomada and Ceelioxys*). 
Compound eyes differ greatly in their size. In some 
insects, as Atractocerus, the drone-bee, many male Mus- 
cide, &c., they occupy nearly the whole of the head ; 
while in others, as numerous Staphylinide, Locusta, &c. 
they are so small as to be scarcely larger than some sim- 
ple eyes of spiders: and they exhibit every intermediate 
difference of magnitude in different tribes, genera, and 
species. 
Under this head I must say something of the Canthus 
of the eye; by which I mean an elevated process of the 
cheek, which in almost all the genera of the Lameilicorn 
beetles enters the eye more or less, dividing the upper 
portion from the lower. Though usually only a process of 
the cheek, yet in the Scarabaide the whole of that part 
forms the canthus*. It only enters the eye in the Ru- 
telide, Cetoniade, &c.; it extends through half of it in 
Copris ; it goes beyond the half in Ateuchus ; and in Rys- 
sonotus it quite divides the eye into two‘, as I before 
observed. In Lucanus, Passalus, &c. it projects before 
the eye into an angle; in Lucanus femoralis nearly into 
* Mon. Ap. Angi. i. 148. > Prate XXVIII. Fic. 4. h’. 
* This circumstance proves that Mr, W.S. Macleay is correct in 
considering this as a subgenus; but it militates against its being 
connected with Lamprima. 
