84 



THE BIOLOGY OF INSECTS 



have described the main features of the compound eyes 

 which are particularly characteristic of insects and of their 

 relations the Crustacea. 



The pair of convex, dark compound eyes present, in 

 most insects, a conspicuous feature of the head. Each eye 

 may occupy a comparatively small round or oval area as in 

 a bug or beetle, or may assume an extensive protruding 

 sub-spherical form as in a breeze-fly or a dragon-fly. 



Fig. 28. — Section through Compound Eye of Honey Bee (Apis 

 mellifica). c, cornea ; o, ommatidia ; b, basement membrane ; p, peri- 

 opticon ; e, epiopticon ; op, opticon. X 100. After E. F. Philips 

 {Proc. Acad. Nat. Sci. Philadelphia, 1905). 



Examining with low magnification the surface of such a 

 compound eye it is seen to be made up of many small, 

 usually hexagonal areas which may be numbered by 

 hundreds or even by thousands. Examination of a section 

 cut through the eye (Fig. 28) vertical to its surface demon- 

 strates that the elements of which it is composed are arranged 

 so as to converge from the inner face of the cuticle (where 

 each element is in contact with one of the small hexagonal 



