260 CLAUDE FULLER. 



This leads me to suggest that fiirther light might be thrown 

 upon the subject of polymorphism by inquiring into the 

 origin of fertile forms of a community of fungus groAvers. 



It is conceivable that conditions within the nest have 

 become so peculiar and artificial, as it were, that it is the 

 fertile caste which requires special food in order to develop, 

 and that under the ordinary conditions obtaining in the nest 

 the abridged development is the normal course. The indi- 

 viduals ultimately becoming winged males and females assume 

 an imago character after the first ecdysis, as then the vestiges 

 of wings arise. Possibly these forms have received some 

 special treatment in the course of tlie first instar. Early they 

 develop distinct characters by which they can be recognised, 

 e.g. wing-sacs. They certainly have a greater opportunity 

 for taking food because their pre-adult existence is prolonged, 

 and it may be accepted that they receive special and generous 

 nutrition, even if there is no direct evidence on this point. 



Should the winged forms arise in a manner of this sort it is 

 not extremely difficult to account for pteroergates, for the 

 vestiges of wings these possess and for their occasional 

 additional features. Pteroergates may then be regarded as 

 forms partly treated or ineffectively treated. 



Unabridged development cannot be caused by a seasonal 

 influence, as, if it were, the community w^ould be generally 

 affected and the winged forms would come to maturity in a 

 very regular manner. But this is not so. Individuals that 

 Avill become males or females begin to appear some time after 

 the last of the previous brood of winged images has left the 

 nest, and the ultimate number produced in a season is due to 

 a gradual augmentation over several months. Indeed, at 

 ■certain times with many species imago nymphs are in great 

 variety as regards the degree of their development, and later, 

 when some are winged and quite mature, others are far from 

 full developmeut. Undoubtedly any general exodus of 

 winged individuals is delayed until a propitious moment, and 

 when that moment arrives the majority are capable of 

 participating in it. 



