ij| ANTS. 



ing. to the following genera: L'ampotwtiis, Pulyrhachis, Mynnicaria, 

 L'l-cuiustogastcr, Plicidoie, Catanlacns, Atopomyniic.r, Poncra and 

 .liioinnut, and to species very closely related to living forms of the 

 same territory if not identical with them. In a specimen of copal 

 from Demerara in the same collection there is a worker Aztcca. 



In reviewing the Tertiary and Quaternary ants one is impressed 

 with two facts that have not been emphasized in the preceding pages. 

 ( )ne of these is the close similarity of some of the ants of the Baltic 

 amber to species now living in the same region. So intimate is this 

 similarity that it may. in a few cases at least amount to identity, c. g., 

 in Poncra atat'ia, Lasins schicffcrdeckcri and Formica flori which 

 neither Alayr nor myself have been able to distinguish by any satis- 

 factory characters from the living Poncra coarctata, Lasnis nigcr and 

 Formica fitsca! Such cases bring home to us very forcibly the enor- 

 mous age and stability of species which the student, dealing exclusively 

 with living forms, would be inclined to regard as of very recent origin. 



The second fact is one to which attention seems not to have been 

 called by previous authors, namely, the absence of polymorphism in 

 the workers of the Tertiary ants. There are, indeed, differences in 

 stature between workers of the same species, but I have seen no speci- 

 mens with sufficient differences in the size and shape of the head to 

 indicate the existence of soldiers and workers proper. This is the 

 more noticeable, because there are recorded from the amber several 

 genera whose living species have polymorphic workers, such as Anonuna, 

 Aeromyrma, Oligomyrmex, Cainponotus and Dimorphomyrmex. The 

 known specimens of Aeromyrma and Oligomyrmex are all males and 

 females, so that nothing is known concerning the workers, which may 

 have been monomorphic. To the former genus belongs also, accord- 

 ing to Emery, the Phcidologeton an'tiqnus described by Mayr from a 

 female specimen. The occurrence of Anomina in the amber is very 

 doubtful. There remain then only the genera Camponotns and Dimor- 

 phomyrmex in which we might expect to find polymorphic workers. 

 I have examined a number of specimens of the three species of Cam- 

 ponotns (mcngei, igneus and constrictus} described by Mayr, but all 

 of them have the form of the minor workers of our existing Componoti. 

 Dinwrphomyrnic.r thcryi was based on a single specimen, but several 

 others which I have seen are monomorphic and in this respect unlike 

 the living type of the genus from Borneo. It may be objected, of 

 course, that no conclusions as to the presence or absence of poly- 

 morphism in the workers can be drawn from the amber material, both 

 because it is too meager and because the soldiers do not forage like 

 the workers and would not therefore be caught in the liquid resin. 



