THE SOCIAL INSECTS 



fifth days seems to be most important, and there seems to be 

 a short period when the grub can be most readily diverted 

 from a worker into a soldier. The first group of eggs laid 

 by a young queen is, however, incapable of producing 

 soldiers even if the eggs are removed and given to an older 

 colony for rearing. Soldiers can be produced only from eggs 

 laid in the second or later batches of the queen. 



In experiments by Wesson, on an American species of 

 Leptothorax, an effect of food on the production of queens 

 was shown. Grubs from one colony were made up into two 

 groups of forty-four and put with workers in artificial 

 nests. One lot were given abundant food, the other just 

 enough food to allow growth and to prevent cannibalism. 



The results were as follows : 



WELL FED POORLY FED 



Initial number of grubs 44 44 



Died during the experiment 6 9 



Formed pupae 38 35 



Produced males 3 2 



„ queens 32 10 



„ workers 3 23 



It seemed, however, that food supply was not the whole 

 explanation, since grubs present during the summer did not 

 respond to such treatment. Only grubs which had over- 

 wintered were responsive in such experiments. 



Brian has very recently found some confirmatory evidence 

 in the British ant, Myrmica rubra. He finds that the grubs 

 of this ant all pass the winter in the third moult stage, 

 though they vary greatly in size ; the biggest ones are ten 

 times as heavy as the smallest. In the spring, when the 

 colony wakes up to life, the biggest ones develop into queens, 

 the rest into workers. If the ratio between nurses and grubs 

 is altered experimentally the proportion of queens and 



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