_M. f. noveboracensis_: 26 specimens in transitional pelage taken in autumn and 14 taken in spring; _M. f. occisor_: One topotype has acquired one-fifth of the winter pelage on October 22, 1896; _M. f. primulina_: 2 in November, one in March, and 2 in April are in process of change; _M. f. spadix_: 6 autumnal specimens and one in April show pelage change; _M. f. longicauda_: 7 autumnal specimens and one in April show pelage change; _M. f. arizonensis_: 12 specimens in autumn and 3 in spring are in process of molt; _M. f. effera_: One November-taken male has acquired four-fifths of the winter coat and another taken on April 21 at Fort Rock, Oregon, is half finished with the spring molt.
It may be added that no marked difference in time of either autumnal or spring molt is apparent as between the more northern and more southern localities from which the mentioned specimens come. With more complete material I would expect to find a difference in this regard.
The material of the other, more southern, subspecies of _Mustela frenata_ has not been adequate to show the time of molting or the number of molts which occur in one year.
Animals in the northern part of the range of _Mustela frenata_ acquire a white winter coat, whereas those in the southern part acquire a brown winter coat, and in an intervening area the winter coat may be either brown or white. By plotting on a map the localities of capture of all specimens examined in the winter coat, it was possible to outline this intervening area as shown in figure 10 on page 37. However, Dearborn (1932:36) shows that in Michigan some animals have a brown coat in winter at places farther north than figure 10 shows to be the case. Hamilton's (1933-306) map for New York shows the same to be true in that state. Accordingly, the boundaries of the area shown in figure 10, in which both brown and white long-tailed weasels occur in winter, are known to be only approximate; with full information available the belt would be represented as wider.
[Illustration: FIG. 10. Map showing the region (in black) where both the brown and white winter pelage is found in the long-tailed weasel, _Mustela frenata_.]
Hamilton (1933:302) has pointed out that "Where half of the weasels remain brown, these brown winter specimens are always males." The results of my own examination of specimens not studied by Hamilton, in a general way provide confirmatory data. More exactly, my examination reveals that at the most northern localities where brown specimens occur, only males are in this coat. In explanation, it may be said that in plotting on a map localities of capture of specimens in the winter coat, thirteen places were found where both sexes were represented and where both brown and white winter coats were found. With the two sexes, it is theoretically possible to have nine different combinations of coat color. With males all brown, there might occur females (1) all brown, (2) all white, or (3) some brown and some white. In addition to these three combinations, we might have three more by finding the mentioned types of female coat color repeated where all males are white, and three more, or nine in all, by substituting a population of males some of which were brown and some of which were white. Seven of these possible combinations actually were found. The two combinations not found were all white males with all brown females, and all white males with females both brown and white. In the three instances where the males all were brown and the females all were white, the localities of capture were in the northern part of the variable area. This indicates that where the brown winter coat occurs at northern localities, the brown individuals are all males. Farther south, of course, the females, too, acquire the brown winter coat.