_Specimens examined_ (3).--2 mi. N, 5 mi. W Ludlow, 2; 1/2 mi. W Reva,
1.
This harvest mouse is uncommon in northwestern South Dakota, although
the species probably occurs sparingly in upland grassy habitats
throughout Harding County. Our specimens, along with one in the
collections of the University of Michigan Museum of Zoology, not
previously reported, from 11 mi. S Mandan, Morton Co., North Dakota,
represent the northernmost known records of this mouse.
A young adult female, obtained on June 21, carried three embryos that
measured 17 and was in summer pelage; an adult male taken on June 27
still was in a worn winter pelage.
At the locality 1/2 mi. W Reva, where traps were set in sparse to
relatively lush grassy areas along South Dakota Highway 20, the
following small mammals were taken in the same trapline (or adjacent
lines) in which one plains harvest mouse was captured: _Spermophilus
tridecemlineatus pallidus_, _Reithrodontomys megalotis dychei_,
_Peromyscus maniculatus nebrascensis_, _Microtus ochrogaster haydenii_,
and _Microtus pennsylvanicus insperatus_.
~Peromyscus leucopus aridulus~ Osgood, 1909