1907.] Wheeler, The Polymorphism of Ants. 73 



the mandibles and of the muscles which are to move them, is regulated 

 according to the amount of formative substance remaining. Perhaps 

 phylogenetic factors also enter into this process and, with the absence of 

 sufficient substance, also phenomena of atavism in the form of a certain 

 stress on the phylogenetically older structures. 



"As a result of these processes we find that when one of two metamor- 

 phosing larvse has a large abdomen its head will be relatively smaller than 

 that of the other, because there remains a relatively smaller amount of 

 larval food substance." 



Towards the end of his paper (pp. 608, 609) Emery still further elab- 

 orates this view and concludes with the following remarks: "The deter- 

 mination both of the relative size of the various regions of the body and of 

 the individual organs to one another may be regarded as a struggle among 

 the parts (Kampf der Theile) of the organism. In the metabolic insects, 

 in particular, this struggle may be divided into two periods : 



"During the first period, which may be of long duration, food supplies 

 are accumulated in an indifferent manner as the larval fat-body while at 

 the same time the rudiments of the imaginal organs arise and prepare 

 themselves for the struggle. 



"During the second period the struggle among the rudiments actually 

 sets in and must be particularly acute in cases where the store of food is 

 meager on account of underfeeding of the larva. The struggle will be 

 decided in favor of the rudiments which are capable of most vigorously 

 appropriating the nourishment. 



"To this struggle is due the regular tv-pe of polymorphism as it is ex- 

 hibited by worker ants in its definite relations to the volume of the body. 

 But before this struggle takes place, the result is already decided, because 

 the ability of the individual imaginal rudiments to attract the larval food 

 reserves has been determined. We may therefore assume that during the 

 first period, by a process still completely unknown, there is a determination 

 of the growth energy of the individual imaginal rudiments which, in the 

 second period, will struggle for the possession of the limited supply of larval 

 food. We may further assume that during the first period, through the 

 relations of the imaginal rudiments to one another and to the amount of 

 larval food substances, the type of the individual, whether female, worker, 

 pseudogyne, etc., as well as its size, is determined. These peculiarities, 

 however, do not manifest themselves till the second period. 



"As trophic poI>/rnorphism the poh/morphism of the female .tex in ants 

 is a function of the distribution of the nutritive substances accumulated during 

 larval life, a distribution which in turn is determined by the struggle among 

 the imaginal rudiments." 



