The Life of the Individual 129 



attempts to do by keeping the bees in the cellar or by pack- 

 ing the hives during the coldest months. As will be explained 

 in the chapter on wintering, the character of the food is 

 an important factor in the reduction of the necessary labor. 



Possible determining factors. 



The cause of the wearing out of bees is not fully under- 

 stood, because there are so many phases of bee physiology 

 about which we are ignorant. An old bee loses the hairs 

 on the body and the wings often become frayed. These 

 parts are not replaced, since in the adult they are non-hving 

 chitinous structures, but it can scarcely be believed that 

 these factors are sufficient to cause the death of the insect. 

 The fact that the larger number of bees die outside the hive 

 during the active season perhaps lends weight to a belief 

 that worn-out wings have failed to carry them back. How- 

 ever, if bees are confined in a cage and are constantly stimu- 

 lated, they wear themselves out and die, when wings could 

 be of no help to them. Koschevnikov ' has described the 

 fat body of the bee and records that in old age the fat cells 

 become less vacuolated and the cells are filled with a granu- 

 lar plasma, while the cells become united into a syncytium, 

 in which the cell boundaries are lost and the nuclei remain 

 distinct. The oenocytes are rather mysterious cells, found 

 in the fat bodies of insects. In the old bee, these become 

 filled with yellow granules, which Koschevnikov thinks are 

 excretory products which cannot be eliminated but are 

 simply retained by the cells. These facts suggest the possi- 

 bility that old age in a bee is due to lack of the excretory 

 function of these cells, but far more evidence is necessary 

 for adequate explanation. 



Some comparisons with other insects help to make clear 

 the difficulty of the problem which confronts us in the 

 phenomenon of old age in the bee.^ Worker ants have been 



> Koschevnikov, G. A., 1900. Ueber den Fettkorper und die CEnocyten 

 der Honigbiene {Apis mellifera, L.) Zool. Anz., XXIII, pp. 337-353. 

 ' For an interesting discussion of the duration of life, the reader is re- 



