54 3IANUAL OF THE APIARY. 



triangle, in the vertices of whose angles are the ocelli. 

 Rarely there are but two ocelli, and very rarely but one. 



The simple eyes (Fig. ^,fff) are circular, and possess a 

 cornea, lens and retina, which receives the nerve of sight. 



From the experiments of Eeaumur and Swammerdam, 

 which consisted in covering the eyes with varnish, they con- 

 cluded that vision with these simple eyes is very indistinct, 

 though by them the insect can distinguish light. Some have 

 thought that these simple eyes were for vision at slight dis- 

 tances. Larvae, like spiders and myriapods, have only sim- 

 ple eyes. 



The compound eyes (Fig. 2, e) are simply a cluster of sim- 

 ple eyes, are situated one on either side of the head, and vary 

 much in form and size. Between or below these are inserted 

 the antennae. Sometimes these last are inserted in a notch 

 of the eyes, and in a few cases actually divide each eye into 

 two eyes. 



' The eyes may meet above as in drones (Fig. 4), most two- 

 wing flies and dragon-flies, or they may be considerably sepa- 

 rated, as in the worker-bees (Fig. 5). The separate facets or 

 simple eyes, of each compound eye, are hexagonal, or six- 

 sided, and in the microscope look not unlike a section of 

 honey-comb. The number of these is prodigious — Leeuwenhoek 

 actually counted 12,000 in the eye of a dragon-fly — while 

 some butterflies have over 17,000. The compound eyes are 

 motionless, but from their size and sub-spherical shape, they 

 give quite a range of vision. It is not likely that they are 

 capable of adjustment to accord with diiferent distances, and 

 it has been supposed, from the direct darting flight of bees to 

 their hives, and the awkward work they make in finding a 

 hive when moved only for a short distance, that their eyes are 

 best suited to long vision. 



Sir John Lubbock has proved, by some interestingexperiments 

 with strips of colored paper, that bees can distinguish colors. 

 Honey was placed on a blue strip, beside several others of 

 various colors. In the absence of the bees he changed the 

 position of this strip, and upon their return the bees went to 

 the blue strip rather than to the old position. Our practical 

 apiarists have long been aware of this fact, and have con- 

 formed their practice to the knowledge, in giving a variety of 



