THE EVOLUTION OF ANTS 



amber are exquisitely preserved (Fig. 1), having been 

 enclosed in it much as insects are mounted in our laboratories 

 in Canada balsam, so that they may easily be compared with 

 existing ants, though the amber was formed millions of years 

 ago. All this material, as well as that found in other forma- 

 tions and studied by others, shows that though the fossil ants, 

 with a few doubtful exceptions, belong to extinct species, 

 most of them belong to existing genera, and that none of 

 the species is more primitive in structure and habits than 

 many now existing. Indeed, many of them are quite as 

 highly specialized as the most specialized existing forms. 

 We are therefore unable to detect any significant evolution 

 of the ants as a whole during the millions of years of Tertiary 

 time, though many species have undoubtedly become extinct 

 and others have arisen through relatively slight variations 

 during that time and have given rise to the ants now living. 

 We find, preserved in amber, even the larvae and pupae of 

 certain ants, some of the plant lice which they tended, and 

 a few characteristic ant guests (Paussidae) and parasites 

 (mites). All this might seem to indicate that there has 

 been no notable evolution of the group, but only a gradual 

 extinction of species among a very considerable number that 

 were suddenly created and distributed over the globe, but 

 such a conclusion is unwarranted. We are bound to assume, 

 on the contrary, that the significant vespoid or wasp-like 

 forms among which the ants had their origin must have 

 lived before Tertiary time-^that is, during the Cretaceous 

 period, or even during earlier Mesozoic time, which, unfor- 

 tunately, is represented by few fossil insects, even of other 

 groups. The only important conclusion we are at present 

 justified in drawing is that the ants are a very old group of 

 insects, which long ago attained essentially its present stage 

 of evolution and has since been marking time or changing 



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