POLYMORPHISM. in 



generalized characters. It is more than probable, as I shall attempt 

 to show in the sequel, that this differentiation was manifested in the 

 sphere of instinct long before it assumed morphological expression. 

 The social wasps and bumble-bees are still in this stage of sociogeny. 

 The ants, however, have specialized and refined on these conditions 

 till they have not only a single marked alimentative and protective 

 caste without wings and lacking many other female characters, but 

 in some species two distinct castes with a corresponding further divi- 

 sion of labor. In the phylogeny as well as the ontogeny these charac- 

 ters appear as a result of nutricial castration. 1 



If the foregoing considerations be granted the biogenetic law may 

 be said to hold good in the sociogeny of the ants, for the actual onto- 

 genetic development of their colonies conforms not only to the purely 

 conjectural requirements of phylogeny but also to the stages repre- 

 sented by the various extant groups of social insects. It is clear that 

 we cannot include the honey-bee among these groups, since this insect 

 is demonstrably so aberrant that it is difficult to compare it with the 

 other social insects. 



Comparison of the different genera and subfamilies of ants among 

 themselves shows that some of them have retained a very primitive 

 social organization, and with it a relatively incomplete polymorphism, 

 whereas others have a much more highly developed social life and a 

 greater differentiation of the castes. Such a comparison, coupled with 

 a study of the natural relationships of the various genera as displayed 

 in structure, shows very clearly that the advance from generalized to 

 highly specialized societies did not follow a single upward course dur- 

 ing the phylogeny, but occurred repeatedly and in different phyletic 

 groups. And since the complications of polymorphism keep pace with 

 those of social organization, we may say that the differentiation of the 

 originally single worker caste into dinergates, or soldiers on the one 



"Nutricial castration" (from rnttri.r, a nurse), as understood by Marchal, 

 must be distinguished from "alimentary castration" (Emery, 1896/0), although 

 both are responsible for the infertility of the worker. Through alimentary 

 castration the development of the reproductive organs is inhibited in the larva 

 and pupa, and this inhibition is maintained in the adult by the strong nursing 

 instincts which prevent the workers from appropriating much of the food 

 supply of the colony to their individual use. In many of the higher animals 

 also (birds, mammals) reproduction is inhibited by the exercise of the nutricial 

 function. A third method of inhibiting or destroying the reproductive func- 

 tion is known to occur in the " parasitic castration " of certain bees and wasps 

 (Andrena, Polistcs) by Strepsiptera (Stylops, Xcnos, etc.). See Perez, " Des 

 Effects du Parasitisme des Stylops sur les Apiaires du Genre Andrena," Actcs 

 Soc. Linn. Bordeaux, 1886, 40 pp., 2 pis. Westwood has also described a 

 Strepsipteron (Mynnccola.v uictneri) which, in all probability, produces this 

 form of castration in certain Formicida? (1861). 



