ECOLOGY OF ISLE ROYALE. 401 



stripe becomes black and conspicuous ; lower parts whitish or yellowish ; 

 above olivaceous or suffused with rufous but much paler than S. iiud- 

 sonicus loquax in the corresponding pelage, soles bare, and the pelage 

 short. A few immature specimens (Nos. 33072, 33074, 33076, 33078) 

 taken between July 27 and Aug. 11, are quite as gray as the January 

 specimen, the lateral black line and the under parts corresponding 

 closely to it. An adult male (No. 33050) belongs in the same category 

 but is even more gray than either winter skin. The amount of fur on 

 the soles is perhaps the most marked seasonal change with such speci- 

 mens. In other words, the seasonal color changes are not well developed 

 in some specimens. 



It is evident from the above observations that, if the two winter speci- 

 mens are representative, the seasonal color changes are much less pro- 

 nounced in liudsonicus (some individuals, in all probability, hardly 

 changing in color at all) than in S. hudsonicus loquax. This of course 

 does not mean that there are no moults, but that moulting is not accom- 

 panied by a marked color change. Such observations also suggest that the 

 Eed Squirrels, in the northern part of their range, may not show as 

 marked seasonal color contrast as is seen farther to the south. But this 

 point can only be definitely determined by the aid of a larger series of 

 winter specimens than are at present in the Museum collection. From 

 a somewhat different point of view, Allen ('98, p. 253) remarks "All 

 the forms of the /S^. hudsonicus group present two well-marked phases 

 of individual color variation, particularly in the summer pelage, namely, 

 a rufous phase and an olivaceous phase, the former usually predomi- 

 nating in about the ratio of 4 to 3, with a considerable proportion of 

 intermediates, which connect the two principal phases. The two princi- 

 pal phases are usually so well marked that were they separated geograph- 

 ically, it would be natural to regard them as subspecies. For this reason 

 a small series of specimens from a given locality is apt to be unsatis- 

 factory." 



Allen's law of the increase of intensity of color from the north south- 

 ward is well illustrated by the Eed Squirrels in Michigan. The paler 

 form, S. hudsom&us, occurs to tlie north, on Isle Royale, and the brighter, 

 more rufous forms Tmdsomcus loquax to the south, in the remainder of 

 Michigan. It is also worthy of note that the seasonal contrasts in pelage 

 are apparently less marked in the northern than in the southern part of 

 the State. 



Geographic Range. — ^The typical form of the species has an extensive 

 northern transcontinental range from Labrador, New Brunswick and 

 Vermont, westward to the north shore of Lake Superior in Ontario; 

 Isle Eoyale, Michigan; North Dakota; Manitoba; Mackenzie basin to 

 Alaska and the Pacific Coast. 



This extensive geographic range in the Canadian forested region and 

 in Alaska is of special interest. The far northern range of this form 

 and its great abundance suggest that it is well adapted to the region it 

 inhabits. It is evidently a Glacial or post-Glacial migrant into most of 

 its present northern range, as the entire area (excepting part of Alaska) 

 lies within the region glaciated by the Wisconsin ice sheet. It seems 

 probable therefore that, at the time of the maximum extension of this 

 sheet, this squirrel frequented largely the coniferous forests at its south- 



