76 Bulletin American Muscuyyi of Natural History, [Vol. XXIII,. 



itive and more 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 practically still in this stage of soci- 

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

 till they not only have a single marked alimentative and protective caste 

 without wings^ and lacking many other female characters, but also in some 

 species two distinct castes with a corresponding further division of labor. 

 Both in the phylogeny and the ontogeny these characters appear as the 

 result of nutricial castration. 



If the foregoing considerations be granted the biogenetic law may be 

 said to hold good in the sociogeny of the ants, for the actual ontogenetic 

 development of their colonies conforms not only to the purely conjectural 

 requirements of phylogeny but also with the stages represented by the va- 

 rious 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 them- 

 selves 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 differ- 

 entiation 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 during the phylogeny, but occurred 

 repeatedly and in different phyletic groups. And since the complications 

 of polymorphism kept 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 hand and micrergates, or small workers, on the other, 



1 Emery (Zur Kenntniss des Polymorphismus, etc., loc. cit., pp. 628, 629) has recently restated 

 his opinion that the females of the primitive ants were wingless, like the workers of existing 

 species, and acquired wings during the phylogeny, an opinion to which he was led by deriving 

 the ants from Mutillid-like ancestors. McClendon and I (Dimorphic Queens, etc., loc. cit., p. 

 161, 162) dissented from this view on the ground that there is no known case among insects of 

 a reacquisition after loss of these organs. Emery replies that they have not been lost but still 

 exist in the germ-plasm of the female Mutillid, "since she produces males with perfect wings. 

 He believes that the wings of existing female ants are an inheritance from the male. The possi- 

 bility of such an inheritance cannot, of course, be disputed, but when the matter is so largely 

 conjectural, the simpler hypothesis maintained by McClendon and myself seems preferable. It 

 is certainly easier to believe that both Mutillids and ants are derived from a common ancestor 

 with both sexes winged, and that the wings were retained by the worker ants, as they are still 

 in the social bees and wasps, till these castes had been definitely established, than to assume a 

 loss followed by a reacquisition of these organs in the queens. Moreover, there is no known 

 case in which an organ has been completely transferred to the opposite sex. Even cases like 

 the vestigial mammae of mammals and the "antlers of the female reindeer are best explained as 

 characters once equally developed and functional in both sexes. (See Lydekker, The Deer of 

 all Lands, London, Rowland Ward, 1898, p. 10). The ergatoid and gynsecoid characters of 

 male ants referred to by Emery, may indeed be inherited from the workers and females respec- 

 tively, but they are modifications of well-developed and functional organs of the male. This 

 case is therefore not strictly comparable with the transfer of whole organs like the wings with 

 their complicated musculature, venation, etc., from one sex to the other. 



