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The White Mountain Butterfly (Neis norna E-ne'is nor'na)

Œneis norna (E-ne'is nor'na) PLATE XXXI, FIG. 5, 8 1 The upper surface of the wings is grayish brown, without spots, except sometimes a minute one in cell M, of the fore wings; the fringe of the wings is brownish white interrupted with blackish brown at the ends of the veins. On the hind wings the marbling of the lower surface shows through somewhat. On the lower surface the tip of the fore wings and the greater part of the hind wings are beautifully marbled with blackish brown and grayish white. Expanse one and threefourths inches. The larva feeds upon Carex vulgaris var. hyperborea. The species is either single-brooded or requires two years for the development of a brood.

It is very remarkable in its distribution. It is an Arctic species, but is found also on the higher parts (above 5,000 feet) of the White Mountains and among the Rocky Mountains of Colorado.

These two widely separated colonies of this butterfly are believed to be the remnants of an arctic fauna, which was forced southward during the Ice age. At the close of this period, as the arctic animals followed the retreating ice northward, the tops of these mountains became colonized by the cold-loving forms. Here they found a congenial resting-place; while the main body of their congeners, which occupied the intervening region, was driven northward by the increasing heat of the lower land. And here they remain clinging to these islands of cold projecting above the fatal sea of warmth filling the valleys below.