Southward Extension of the Arctic Zone

Extract

Many of the Arctic species live above timberline in mountainous areas far to the south of the Arctic. We have made collections in such areas a t two places in North America, the Front Range of Colorado and the Banff National Park area in Alberta.

Because of a geological accident, the existence of hundreds of square miles of peneplain at and above timberline (11,500 to 13,000 ft.), Colorado has a very extensive Arctic fauna. However, the main mountain mass in Colorado is far removed from the Arctic and isolated by at least a hundred miles of prairie and forest. The fauna above timberline in colorado is composed of about one third truly Arctic species, one half widespread Cordilleran species, and a small number of endemic species derived from the local fauna in Colorado. Perhaps the most characteristic difference between the insect fauna of the Colorado tundra and that of the Canadian Arctic tundra is the occurrence of a rich fauna of Heteroptera in the Colorado tundra, contrasting with an almost total lack of this group in the Canadian Arctic. Vegetationally the story is similar, the outstanding characteristic of the Colorado tundra being the almost complete lack of Ericaceae.