stus_ and the
subspecies to the north on Figure 2 is drawn somewhat arbitrarily
because few specimens are available from this area. Actual
intergradation, in the form of a geographically intermediate population
also morphologically intermediate between these two subspecies, is
lacking. However, in most populations of both subspecies some
individuals are intermediate between the two subspecies or even more
like the other subspecies than the one to which they are referred.
Warren (1942:226) states that _modestus_ has been recorded from Lake
County, although no reference to a specimen is given. Bailey (1900:21)
cites Twin Lakes, in Lake County. That county is near the dividing line
as I have drawn it, and therefore specimens from Lake County would be
of special interest. An isolated colony of _modestus_ occurs at San
Rafael in Valencia County, New Mexico (Bailey, 1932:201). A hiatus of
approximately 150 miles separates that colony from the southernmost
locality shown in Figure 2. A single specimen, the skin of an immature
_Microtus_ without skull, from Trinchera, Colorado, taken by L. R.
Hersey in 1912, is in the Colorado Museum of Natural History. No
species of Microtine has been recorded from within 50 miles of this
locality. The specimen is seemingly more like _M. pennsylvanicus_ than
any other species of _Microtus_. This locality is represented in Figure
2 by a question mark. Ecologically _M. montanus fusus_ Hall and _M.
longicaudus mordax_ (Merriam) in the same region occupied by _modestus_
seem to be more montane than _modestus_. It favors lush grass on the
wet floors of alluvial valleys, and also irrigated areas such as that
at Manassa.

_Specimens examined._--Total 130. _Colorado_: CHAFFEE CO.: Salida,
3 (ERW). SAGUACHE CO.: Monshower Meadows, 27 mi. NW Saguache [=3
mi. E Cochetopa Pass], 8 (USBS); _Tevebaugh's Ranch, 20 mi. W
Saguache_, 46 (USBS, there are additional specimens not examined in
detail by me); _Cochetopa Pass, 33 mi. W Saguache_, 1; 3 mi. N, 16
mi. W Saguache, 8500 ft., 5; 5 mi. NW Hooper, 1 (AMNH); Medano
Ranch, 15 mi. NE Mosca, 2 (1 ERW, 1 USBS). CUSTER CO.: Westcliffe,
7800 ft., 1 (ERW). ALAMOSA CO.: _Hooper_, 10 (2 AMNH, 8 Denv);
_Mosca_, 3 (ERW). CONEJOS CO.: 1-1/2 mi. E Manassa, 11. COSTILLA
CO.: Alamosa, 3 (Mich); 2 mi. S Blanca, 7800 ft., 6 (MVZ). _New
Mexico_: TAOS CO.: Arroyo Hondo, 7600 ft., 6 (USBS); Taos, Pueblo,
1 (USNM). COLFAX CO.: 1 mi