PHYSIOLOGY AND BEHAVIOR OF THE ARTHROPODA 



345 



the work from then on, including nest building and feeding the pri- 

 maries. The latter continually secrete juices in return for being fed, and 

 these are licked up eagerly by the workers. It is thought that this secre- 

 tion reward is the basic mechanism that integrates the colony, and the 

 phenomenon is called trophallaxis. As the colony grows in size a few 

 of the offspring develop wing buds and become sexually mature; these 

 are called the secondary reproductives. Some of the young develop into 

 sterile, wingless soldiers which must also be fed. 



All of the termites produce secretions to some extent, and these 

 are continually licked up by the workers and by the young nymphs. In 

 this way the colony as a whole develops a blended odor distinct from 

 that of any other colony, a distinction used by the members of a colony 

 in recognizing strangers. Recently it has been suggested that trophal- 

 laxis is a mechanism for distributing substances that act as hormones, 

 and that these determine the kind of individual a young nymph will 

 become. According to this interpretation the reproductives secrete an 

 "anti-reproductive substance" that prevents sexual maturity in the 

 young. Similarly the soldiers secrete an "anti-soldier substance." If the 

 number of either of these groups falls below a critical level, not enough 

 of their "anti" substance will be circulating in the colony and some of 

 the young develop in that direction. This explains the appearance of 

 secondary reproductives after the original colony has become large, and 

 also explains the immediate replacement of any group after it has been 

 removed experimentally. 



Seasonally large numbers of primary reproductives are produced 





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Figure 17.18. Castes of termites. A, Male (king), before shedding wings. B, Female 



(queen), after shedding wings. C, \Vorker. D, Soldier. Workers and soldiers are sterile in- 

 dividuals of either sex. 



