xvm. THE HONEY BEE. 267 



guided by a preference for certain colours ; while his 

 experiments on ants bring out the still more interesting 

 fact that these insects are sensitive to ultra-violet rays 

 quite invisible to us. 



Any one who will take the trouble to examine with a 

 lens the head of a bee, will see on either side the large 

 rounded compound eye, and on the forehead or vertex 



A. B. 



EYES AND EYELETS OF BEE. 

 A Drone. B Worker. 



three bright little simple eyes. The latter are, as their 

 name implies, comparatively simple in structure, each 

 with a single lens. But the compound eyes have a com- 

 plex structure. Externally the surface is seen to be 

 divided up into a great number of hexagonal areas, each 

 of which is called a facet, and forms a little lens. Of 

 these the worker has from 3,500 to 5,000, and the queen- 

 mother nearly as many, while in the drone they are larger 

 and yet more numerous. In the eye of the dragon-fly 

 there are 20 ; 000 of these facets. Between each facet 

 is a crystalline cone, a so-called nerve-rod, and other 

 structures, too complex to be here described, which pass 

 inwards towards the brain. The figure shows a section of 

 the eye of a fly with its facets and cones. 



It will be seen then that the so-called compound eye 

 with its thousands of facets, its thousands of crystalline 

 cones, its tens of thousands of "retinulse" and other 

 elements, is a structure of no little complexity. The 



