SOCIAL TRANSITIONS 267 



alcohol or ether, the males appeared at the usual 

 time, but the females were delayed by twelve or six- 

 teen days on the average. 



Ordinarily in Zootermopsis only one soldier ap- 

 pears in the first year of the life of the colony. By 

 removing the soldier as soon as it appeared in the 

 experimental colony it was possible to get as many 

 as six soldiers within the time that would ordinarily 

 have yielded only one. 



In explanation of these and other similar data 

 Dr. Castle expresses his opinion that at the time of 

 hatching all nymphs possess three sets of possibili- 

 ties to the same degree; namely, they may become 

 sexually mature though wingless, they may become 

 winged and sexually mature, or they may become 

 soldiers. At some stage these chances are narrowed 

 to two possibilities: the nymph may become sexu- 

 ally mature or it may develop into a sterile soldier. 

 Since the reproductive possibility is present in all 

 nymphs and since its expression is inhibited by a 

 substance produced by a functional reproductive and 

 eaten by the nymphs, the absence of functional re- 

 productives would allow this potential power to ex- 

 press itself. Just what determines that one of the 

 first small lot of eggs will become a soldier is not 

 known, but it can easily be seen that when one 

 soldier has started to develop it too may give off an 



