EXTERNAL ANATOMY OF INSECTS. 503 
a spine; but in Lamprima and Aisalus it does not exist. 
The part, also, that enters the eye in the Capricorn 
beetles may be regarded as a kind of canthus, though it 
is merely a dilatation of the front. 
4, Stemmata*.—Having given so full an account of 
the kinds and structure of the ordinary eyes of insects, 
you may perhaps expect that I should now dismiss the 
subject: you would, however, have great cause to blame 
me, did I not make you acquainted with a kind of auxi- 
liary eyes with which a large portion of them are gifted ; 
I mean those pellucid spots often to be found on the poste- 
rior part of the front of these animals, or upon the vertex, 
frequently arranged in a triangle. These, Linné, from 
his regarding them as a kind of coronet, called Stem- 
- mata. They have been of late denominated Ocelli ; but 
as this latter term is also in general use for the eyelets on 
the wings of Lepidoptera, I have adhered to that of the 
illustrious Swede. Neither he nor Fabricius has ex- 
pressed any opinion as to the wse of these organs; but 
Swammerdam and Reaumur were aware that they were 
real eyes. ‘The former found that there are nerves that 
diverge to them though not easily traced, and that they 
have a cornea, and what he takes for the wvea®; and the 
latter has supposed that the compound eyes and these 
simple ones have, the one the power of magnifying ob- 
jects much, and the other but little, so that the former 
are for surveying those that are distant, and the latter 
those that are near*. The same author relates some ex- 
periments that he tried with the common hive-bee, by 
* Prate VI. Fic. 4, 10. VIL. Fie, 1, 2, 4. XXVI. Fic. 39-42. 1. 
> Bibl. Nat. i. 214, © Reaum. iv. 245. 
