iQoS] The Polymorphism of Ants 6i 



vicissitudes before they can establish themselves successfully 

 among alien hosts. I have already emphasized the adaptive 

 significance of the disappearance of the worker caste among per- 

 manently parasitic species like Anergates, Wheeleriella, etc. 



There are several cases in which the worker and female differ 

 greatly in color, pilosity or sculpture, and in such cases either 

 caste may be conservative or aberrant according to ethological 

 requirements. Thus in certain temporary parasites like Formica 

 ciliata, oreas, crinita, dakotensis, and difficilis, the female is 

 aberrant in one or more of the characters mentioned, while the 

 cospecific worker retains the ancestral characters of the same 

 caste in the closely allied forms of F. rufa. The same condition 

 is seen in a very different ant, Aph^nogaster tennesseensis, as 

 the result of similar parasitic habits. In all of these species the 

 females alone have developed myrmecophilous characters, like 

 the long yellow hairs of F. ciliata, or the mimetic coloring of F. 

 difficilis, which enable them to foist themselves on allied species 

 and thus avoid the exhausting labor of excavating nests and 

 rearing young, whereas the workers remain unmodified. 



The foregoing observations indicate that in morphological 

 characters the worker and female of the same species have ad- 

 vanced or digressed in their phylogeny, remained stationary or 

 retrograded, independently of each other. The same peculiarity 

 is also observable in species with distinct worker and soldier castes. 

 It thus becomes impossible, even in closely related species of cer- 

 tain genera, like Pheidole, to predict the characters of the worker 

 from a study of the cospecific soldier or vice versa. And while 

 adaptive characters in stature, sculpture, pilosity and color must 

 depend for their ontogenetic development on the nourishment 

 of the larvffi, it is equally certain that they have been acquired 

 and fixed during the phylogeny of the species. In other words, 

 nourishment, temperature, and other environmental factors 

 merely furnish the conditions for the attainment of characters 

 predetermined by heredity. We are therefore compelled to agree 

 with Weismann that the characters that enable us to dift'erentiate 

 the castes must be somehow represented in the egg. We may 

 grant this however, without accepting his conception of represen- 

 tative units, a conception which has been so often refuted that it is 

 unnecessary to reconsider it in this connection. 



Having touched upon this broader problem of heredity it will 

 be necessary to say something about the inheritance or non-inher- 



