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 formations 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, unfortunately, 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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