1904 



GLEANINGS IN BEE CULTURE. 



383 



THE COMPOUND EYES OF THE BEE. 

 A Scientific Examination of tliis Wonderful and Complicated Organ. 



BY E. F. PHILLIPS. 



An examination of the large compound eyes of a bee will 

 show that the (ulside is made up of hexag-onal areas, 

 thousands in number. Each of these hexagons is the out- 

 side of one of the elements of which the o mpound eye is 

 composed; and, since they are all constructed alike, a de- 

 scription of one will serve for all. Each of these elements 

 is called an ommatidium. If, then, we take a section 

 through one of the compound eyes parallel with the top of 

 the head of the bee we shall get some of these cut length- 

 wise, and these show best the structure, although it is also 

 necessary to cut other sections at right angles to this plane 

 in order to get the shape of seme of the parts. The figures 

 which accompany this will show the ommatidium cut 

 lengthwise, and at the side smaller figures showing a sec- 

 tion at right angles at the points indicated by the dotted 

 lines. Ano'her figure shows an ommatidium from a sealed 

 larva, or, more properly called, the pupa stage, since the 

 word larva should be applied only to the unsealed brood. 



The outside por ion, already mentioned, is the lens 

 layer, a, and is composed of chitin, as is all the rest of 

 the outside covering of the bee The secion shows this as 

 cut, so that only two sides cf the hexagon are shown. while 

 the smaller figure shows the hexagonal shape. This lens 

 layer is secreted b3 the two small cells, b, which show 

 much more clearly in the pupa stage before the chitin is 

 formed, since they keep getting smaller and smaller as 

 the bee grows, until they finally remain only as very 

 small remnants. 



The next lower structure is the crystalline cone, c, 

 which is composed of four cells, of which only two show in 

 the long section. In the pupa 

 stage the boundaries are much 

 clearer, and the nuclei larger 

 than they are in the adult eye. 

 This cone is clear, and, like the 

 lens abcve it, gathers in the 

 light raj's so that they can act 

 on the nerves below just as the 

 lens in the human eye gathers 

 together rays of light so they can 

 afF- ct the nerves behind it. 



Directly in line with the cone 

 is a long rodlike structure which 

 runs clear to the bottom of the 

 ommatidium, called the " rhab- 

 dcme, " d. This probably con- 

 tains the ending of the nerves 

 which are sensitive to light. 

 Around the rhabdome are eight 

 retina cells, e, which have poured 

 out a secretion while in the pupa 

 state to form the rhabdome. In 

 Fig. 2 the rhabdcme is shown as 

 only partly formed, and the ret- 

 ina cells come together below it. 



Around the cone and retina 

 cells there are pigment cells that 

 keep the light ifrom passing from 

 one ommatidium to ihe other, and 

 thus making a confused image, 

 just as the inside of a camera is 

 painted black to avoid reflec- 

 tions. In the human eye we also 

 find pigment, which is located 

 just behind the nerve-endings, 

 and answers the same purpose. 



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I Fig. 1.— Ommatidium from an adult eye 

 Fro. 2.— Ommatidium from eye of of the bee ; a, lens ; b, lens secretiag cells ; 

 puiia of bee. Letters same as Fig. 1.1c, cnne;d. rhabdome; e, retina cells;!, 

 Scale about twice as large as Fig. l.| bottom layer cells. 



