THE TERMITES 



the winged sexual adults are not produced until the colony- 

 is several years old. This last point is another example of the 

 natural balance which is maintained between the members 

 of the various castes. Artificial removal of the royal couple 

 results in the production of substitute sexual forms. 



An interesting experiment has been performed by Castle 

 and others with the soldiers. In the normal course, in a young 

 colony only one larva will be transformed into a soldier. 

 But if the single soldier is removed, another larva or nymph 

 will quite soon be transformed. Moreover, the appearance of 

 the first soldier can be suppressed by introducing one from 

 another nest into the young colony. These results suggest 

 that the presence of sexual forms or of soldiers inhibits the 

 conversion of further nymphs into these castes, at least until 

 the nymphs become very numerous, when the balance may 

 be restored by the production of more individuals of the 

 required caste. 



In another curious experiment Grasse and Noirot made up 

 isolated pairs of fourth stage nymphs of Calotermes. They 

 found that if the pair was one of each sex both became 

 sexually mature after the next moult. But if the two were of 

 the same sex, only one became sexually mature — another 

 example of balanced production of the required castes. In 

 normal colonies of Calotermes, if the royal couple is removed, 

 substitute sexual forms are produced, but only one pair 

 becomes the royal couple and the others are destroyed by 

 the workers. In some other termites, however, a number 

 of substitute sexual forms may reproduce simultaneously, 

 perhaps because their rate of eggrlaying is lower than that 

 of the original queen. 



A final example of social regulation is provided by an 

 experiment by Miller on the American Prorhinotermes. He 

 put a group of 545 similar nymphs into an artificial nest 



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