172 MAMMALS OF PENNSYLVANIA AND NEW JERSEY. 



have tails 5^ to 6 in. long and the females 4^ inches. It should be noted 

 that the size of the females in both species is % to almost y$ less than that 

 of the males (see measurements). On this account small females of nove- 

 boracensis are about the same size as large males of dcognani, but the differ- 

 ence in the length of tail between these is striking. Bonaparte's weasel always 

 turns white in winter even in its most southern distribution, but the N. York 

 weasel in the transition and austral zones very rarely turns white, the winter 

 pelage being merely paler than that of summer. In the most boreal localities 

 of Pa. the N. York weasel turns white in about 25 to 50 per cent, of the cases 

 observed by me. Whether the special conditions of a forested or deforested 

 environment, or of severity of weather or amount of snow-fall, cause this in- 

 dividual variation in winter pelage among the weasels of a given locality, I 

 am unable to say. Regarding the real conditions as they exist in northwestern 

 Pa., Malloy writes : " I do not believe there are any white weasels in summer, 

 but I do know that they are dark brown, light brown, dark red and light red 

 in winter and that I have caught them every week from Dec. i until April /. 

 I caught a dark brown, a dark red and a pure white all in one night but at 

 different places. I never caught a maltese weasel in winter but have caught 

 many of them in summer." This experience tallies exactly with that of Mr. 

 Behr, in Sullivan Co. I have a white winter weasel taken in Camden Co. a 

 few years ago and brought to me in the flesh. Regarding this seasonal change 

 of color in weasels, it should be understood that it is accomplished solely by 

 molting, the new hair, whether brown or white, not altering its color, except 

 from exposure and wear, from the time of its first appearance on the surface 

 of the skin until it is shed again the next season. While this new brown or 

 white coat is growing, the old is slowly falling out, giving sometimes a patchy, 

 at others a peculiar faded, semi-white, appearance. This has given rise to 

 the popular idea that the color of the old hair is changing either to brown or 

 white, as the case may be. In no case of bird or mammal is a fundamental 

 color change caused by the voluntary action of the individual or by any other 

 normal force upon feathers or hair after these have once pierced the skin. 



The pattern of coloration in summer, as well as the tint in the two species 

 now considered, is essentially the same, viz : dark or liver-brown above, in- 

 cluding tail, legs and head except lower jaw, white below, tip of tail black at 

 all seasons ; this tip being relatively long in the large, and short in small, spe- 

 cies. In the larger species the under parts are often pale sulphur yellow. 



Measurements. (dcognani.} Total length, male, 285 mm. (n^ in.), 

 female, 225 (10); tail vertebrae, male, 77 ($%}, female, 69 (2^); hind 

 foot, male, 37 (i^), female, 30 (i^). In the same order, measurements 

 for noveboracensis are : male, 405 ( 16), female, 325 (12^); male, 

 female 108 (4^) ; male, 47 (i^), female, 34 



