SOLITARY AND SOCIAL BEES 



The hereditary factors which are supposed to control the 

 type of development of the individual are represented by 

 letters, the queen having the constitution Aa Bb. During the 

 development of her eggs in the ovary, there is a special cell 

 division (reduction division) in which each group of genetical 

 units (chromosomes) is halved. Thus the Aa Bb queen will 

 produce four types of unfertilised eggs with constitutions 

 AB, Ab, aB, and ab. The males are, as in all bees and wasps, 

 derived from unfertilised eggs, and so have only the half 

 complement of hereditary factors to start with. They omit 

 the reduction division and their sperm are, therefore, of the 

 same four types as the unfertilised eggs. When fertilisation 

 occurs, there will be an equal likelihood for any of the four 

 types of eggs and sperm to meet. Only four out of sixteen 

 possible combinations will give an individual constituted 

 like the queen. Thus sperm AB + egg ab, or sperm Ab + 

 egg aB, would both give a queen. We should therefore 

 expect, on the average, one-quarter of the offspring to be 

 queens and three-quarters workers. Males will be derived 

 from any eggs which are not fertilised. 



The case where one-eighth of the females are queens would 

 arise if three factors were involved and the queen had a 

 constitution Aa Bb Cc. While such schemes can theoreti- 

 cally explain the facts, this is very far from saying that they 

 have been proved to be true. Kerr supposes that some 

 similar arrangement may also exist in Trigona and in the 

 honey bee, but that in them the queen grub has to be given 

 the right quantity or quality of food as well as inheriting 

 the right constitution. In Melipona,-if queens are produced at 

 a constant rate throughout the life of the colony they would 

 soon become too numerous, and Kerr finds that most of 

 them are killed by the workers. 



If Kerr's ideas are substantiated it would seem that 



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