THE SOCIAL INSECTS 



build " royal " cells, usually on the edges of the ordinary 

 comb. These cells are considerably larger than the ordinary 

 brood-cells and produce queens which are larger than the 

 workers. In Melipona and in some kinds of Trigona no 

 special royal cells are recognisable and the queen is no larger 

 than the worker. It is also said that she has to feed up for 

 some time before her ovaries can become active. 



The stingless bees are almost the only group of social 

 insect in which there is no contact between the adult and the 

 grubs. The cells are filled with a food, mainly honey and 

 pollen, and when the egg has been laid the cell is sealed with 

 wax. There is thus no opportunity for the type of differential 

 feeding which is well-known to occur in the honey bee. 

 Moreover, it is stated that several workers may contribute 

 to the storing of each cell, making it much more difficult to 

 suppose that any accurately balanced diet can be provided. 

 While enlarged royal cells would provide the queen grub 

 inside them with a greater bulk of food, this would not 

 apply to Melipona, since the queens and workers develop 

 in similar cells. 



THE THEORY OF HEREDITARY CASTES 



Because of these difficulties, Kerr has recently suggested 

 that the characters of the castes are inherited and are not the 

 result of special feeding. When he bred out the brood from 

 combs removed from nests he found that in three species of 

 Melipona the queens formed one-eighth of all the progeny, 

 while in a fourth species they formed one-quarter. These 

 fractions correspond to what are known in the Mendelian 

 scheme of genetics as a " trifactorial " and a " bifactorial " 

 backcross. The meaning of this description can be explained 

 most simply in the species which produces one queen for 

 every three workers, that is, one-quarter queens. 



IOO 



