+-----
Interorbital
breadth |27| 3.1|( 2.9-3.3) |+-0.12 |28| 3.1|( 2.8-3.3) |+-0.11
-------------+--+-----+------------+------+--+-----+-----------+-----
Breadth of
zygomatic
plate |27| 1.9|( 1.8-2.1) |+-0.10 |28| 2.0|( 1.9-2.3) |+-0.12
-------------+--+-----+------------+------+--+-----+-----------+-----
Breadth of
mesopterygoid
fossa |26| 0.9|( 0.6-1.1) |+-0.12 |28| 0.9|( 0.8-1.2) |+-0.12
-------------+--+-----+------------+------+--+-----+-----------+-----

Pelage and Molt

Western harvest mice that attain adulthood acquire at least three
distinct types of pelage in sequence in the course of their development.
The first of these, the juvenal pelage, is short, relatively sparse, and
characteristically grayish brown. The molt (post-juvenal molt) from
juvenal pelage to subadult pelage seemingly occurs at an early age,
perhaps frequently before the young leave the nest, as individuals in
juvenal pelage are few among specimens studied by us. Judging from study
skins alone, the progress of post-juvenal molt in _R. megalotis_ is
similar to that described for _R. humulis_ by Layne (1959:69-71). The
subadult pelage is thicker, longer and brighter than juvenal pelage and
closely resembles the pelage of adults; it differs from adult pelage
dorsally in being somewhat duller and in having less contrast between
back and sides.

The pelage of adults varies depending on season. In summer the
individual hairs are relatively short (5-6 mm. at the middle of the
back) and sparse. The over-all color of the dorsum, sides and flanks is
brownish to dark brownish, and the venter is grayish. In winter the
pelage is dense, long (8-9 mm. at the middle of the back) and lax. The
over-all color dorsally in fresh winter pelage in most specimens is
paler (more buffy) than summer pelage, the sides are markedly buffy, and
the venter is whitish; even the tail is more pilose and more sharply
bicolored than in summer. Adults molt, usually completely but
occasionally only partially, at least twice a year--once in spring (in
May and June in Nebraskan specimens) from winter to summer pelage, and
once in autumn (in October and November in Nebraskan specimens) from
summer to winter pelage. Of the two molts, the one in spring is most
easily discernible because the contrast in color between worn winter
pelage and fresh summer pelage is considerably greater than that between
worn summer pelage and fresh winter pelage, and bec