g WiLiJAAf Morton Wheeler. 



nisms can not be readily trapped and overwhelmed by liquid resins. 

 But this kind of selective action, has little bearing on our problem, 

 unless we suppose what is not impossible, that large and powerful 

 Ponerince and Camponothue — insects comparable to the Australian 

 species of Myrmecia, the Brazilian species of Paraponera and Dino- 

 ponera or the Malayan Camponotus gigas — niay have lived in the 

 amber forests. The differences of habit, however, are certainly more 

 important. The existing Ponerince are nearly all wary, terrestrial or 

 even hypogaeic ants, which rarely or never climb trees, but seek their 

 insect prey on or under the surface of the o round, and there is every 

 reason to believe that the early Tertiary species had the same habits. 

 As Emery maintains^), this would readily account for the small number 

 of individuals of this subfamily in the material examined. The Myr- 

 micince, too, are largely terrestrial, although several genera, such as 

 Sima, Monomorium, Leptothorax and Crematogaster are very largely 

 or entirely arboreal. Sijna and Leptothorax are, in fact, represented 

 by a fair number of species in the amber, though the number of indi- 

 viduals is scarcely as great as we should expect. Crematogaster is 

 entirely wanting, though from its present cosmopolitan distribution 

 we should certainly expect it to be present. The same is true of 

 Pheidole. It would seem, therefore, that the absence of these and many 

 other common Myrmicine genera, which in all probability existed as 

 far back as the Lower Oligocene, must be due to their never having 

 invaded the Baltic region rather than to the selective action of the 

 liquid resin. The terrestrial habits of many other genera, such as 

 Erebomyrma, Stenamma, Aphceno g aster, My rmica etc., sufficiently account 

 for their small individual representation. Undoubtedly the prepon- 

 derance of the Dolichoderince and Ca^nponotinm, which together constitute 

 nearly 97 °/o of all the specimens, is due to the highly arboreal habits 

 of these ants. The singular disproportion between the individual re- 

 presentations of these two subfamilies is brought about by two species 

 of Dolichoderince^ Iridomyrmex goepperti and I. geinitzi, the former 

 represented by 5428, the latter by 1289 specimens. If we subtract 

 the sum of these (6717) from the total number of Dolichoderince (7508) 

 we have left only 791 individuals, which is certainly much nearer the 

 modern ratio of Dolichoderince to Camponotincs in a tropical forest. 

 The absence of one whole subfamily of ants, the Dorylince, from the 

 Baltic amber, is still to be accounted for, since we can hardly suppose 

 that this group, which is nearly as primitive as the Ponerince, was 



1) Le Fornaiche deU'Ambra Siciliana, etc. loco citato p. 586. 



