MOUNTAIN ANTS OF NORTH AMERICA. 485 



strikingly eurythermal ("eurythermal ubiquists" of Zschokke, 1907, 

 1908). A list of the latter would include the following: 



Myrmica scahrinodis and most of its subspecies and varieties, 



Aphaenogaster suhterranea subsp. occidentalis , 



Tapinonia sessile, 



Prcnoh'pis imparis, 



Lasius nigcr subsp. alienus var. americanus, 



L. brevicornis, 



L. flavus subsp. nearcticus, 



Formica sanguinea subsp. ruhicunda, subintegra and subnuda, 



F. fiisca and its varieties subsericea and argentea, 



F. cinerea var. neocinerea, 



F. neogagates subsp. lasioides var. vetula, 



Polyergus rufescens subsp. breviceps, 



Camponotus herculeanus subsp. pennsyhanicus , 



C. fallax var. nearcticus, 



C. maculatiis subsp. vicinus and its varieties. 



It will be noticed that the bulk of the forms common to all four 

 regions of the tables is made up of some eight of the forms included in 

 this list. The ants of both the preceding lists, owing to their pro- 

 nounced eurythermy or psychrophilous stenothermy, constitute the 

 great majority of the forms common at higher elevations in the moun- 

 tains of North America. Incidentally attention may be called to the 

 high degree of melanism of nearly all the forms enumerated in these 

 lists. This is a well-known peculiarity of many arctic-alpine insects 

 (Cf. Zschokke, 1908, p. 42). 



The ant-fauna of the Nearctic Transition and Boreal Zones as a 

 whole shows very close affinities to the fauna of the corresponding 

 zones of the Palearctic Region, as will be evident from a study of the 

 following list in which the most closely allied forms of the two regions 

 are arranged in parallel columns:— 



Palearctic Nearctic 



Ponera coarctata P. coarctata subsp. pennsylvanica 



Monomorium minutum M. minimum 



Solenopsis fugax S. molesta 



Myrmica sulcinodis M. brevinodis 



M. scabrinodis var. sabuleti M. scabrinodis var. sabuleti 



M. scabrinodis subsp. lobicornis M. scabrinodis subsp. lobicomis var. 



glacialis 



