228 OBJECTIONS TO THE THEOKY Chap. VII. 



arc rcg'ularly produced in l:ir^e numbers, with tlu; iiKiny st4?rilo 

 neuters of the same coininunity. Thus I l>elieve it has been 

 "vvith social insects : a slij^ht modification of structure, or of in- 

 stinct, correlated with tlic sterile condition of certain members 

 of the conmiunity, has been advantageous to the community: 

 consequently the fertile males and females of tlie same cona- 

 munity flourished, and transmitted to their fertile ofl'sprinfr^ a 

 tendency to produce sterile members having the same modifi- 

 cation. And I believe that this process has been repeated, 

 luitil that prodigious amount of difference between the fertile 

 and sterile females of the same species has been produced, 

 which wo see m so many social insects. 



But we have not as yet touched on the climax of the difE- 

 culty : namely, the fact that the neuters of several ants differ, 

 not only from the fertile females and males, but from each 

 other, sometimes to an almost incredible degree, and are thus 

 divided into two or even three castes. Tiie castes, moreover, 

 do not generally graduate into each other, but are perfectly 

 well defined ; being as distinct from each other as are any two 

 species of the same genus, or rather as any two genera of the 

 same family. Thus in Eciton, there are working and soldier 

 neuters, wnth jaws and instincts extraordinarily difi'ercnt : in 

 Cryptocerus, the workers of one caste alone carry a wonderful 

 sort of shield on their heads, the use of which is quite imknown : 

 in the Mexican JMyrmecocystus, the workers of one caste never 

 leave the nest ; they are fed by the workers of another caste, 

 and they have an enormously-developed abdomen which se- 

 cretes a sort of honey, supplying the place of that excreted by 

 the aphides, or the domestic cattle, as they may be called, 

 which our European ants guard and imprison. 



It will indeed be thought that I have an overweening con- 

 fidence in the principle of natural selection, when I do not ad- 

 mit that such wonderful and Avell-established facts at once an- 

 jiiliilate the theory. In the simpler case of neuter insects all 

 of one caste, which, as I believe, have been rendered different 

 from the fertile males and females through natural selection, 

 we may conclude from the analogy of ordinary variations, that 

 the successive, slight, profitable modifications did not first 

 arise in all the neuters in the same nest, but in some few alone ; 

 and that by the survival of the communities with females which 

 ])r()(lure most neuters having the advantageous modification, all 

 the neuters ultimately come to be thus characterized. Accord- 

 ing to this view, Ave ought occasionally to find in the same nest 



