318 Experimental Zoology 



at first to be all alike, and potentially have the power to become 

 workers, soldiers, or substitute royal forms. The workers and 

 the soldiers have rudimentary reproductive organs and are of 

 both sexes. Their development is, in a sense, arrested, although 

 they are something more than simply undeveloped individuals, 

 since they have peculiarities that belong to their caste. The 

 substitute royal forms are, however, according to Grassi, neotenic 

 individuals in which the sexual organs develop, but the wings do 

 not. In this and in some other respects they represent sexually 

 mature larval forms. Although attempts have been made to 

 discover the nature of the food that determines the fate of 

 individuals of the colony, nothing definite has as yet been 

 ascertained. 



Grassi succeeded in establishing colonies in small glass tubes 

 that could be carried about in his waistcoat pocket and studied 

 through the walls of the tube. Colonies of from 15 to 40 indi- 

 viduals of different ages were thus established, made up of 

 workers, soldkrs, and young, but without sexual forms. After 

 a few days, from two to six incipient substitute pairs appeared, 

 characterized by pigmented eyes. In fact, Grassi says, even 

 after 30 or 40 hours in summer he could tell which individu- 

 als would acquire the ocular pigment. The formation of these 

 incipient royal substitutes does not take place if a royal pair is 

 present ; but if the king or the queen is removed for 24 or 48 

 hours, a few substitute forms begin to appear. In one case a 

 nest was made up of only three large larvae, and in two weeks one 

 of these exhibited pigmented eyes, and was in process of be- 

 coming a substitute form. If a nest contains adults ready to 

 fly, i.e. royal forms that have not yet paired, the formation of 

 royal substitutes takes place nevertheless, as described above. 

 In other words, the winged sexual forms if present do not be- 

 come kings and queens, when these are needed in the nest, but 

 substitute forms are made. Only after the nuptial flight do the 

 royal forms become the heads of new colonies. 



The food of Calotermes consists of wood, matter excreted 

 or disgorged by other individuals, the exuviae, the corpses of 



