provisionally referred specimens from Requa and Crescent City, Del Norte
County, California, to _Z. t. eureka_. I have studied this material and
find the specimens to be intermediate between _Z. t. trinotatus_ and _Z.
t. eureka_ in cranial characters (zygomatic breadth, interorbital width,
and breadth of braincase), but nearer _Z. t. trinotatus_ in coloration
(absence of ochraceous suffusion ventrally). They are here referred to
_Z. t. trinotatus_. The zone of intergradation between _Z. t.
trinotatus_ and _Z. t. eureka_ seems to extend from Requa, California,
north to Gold Beach, Oregon, where other specimens intermediate between
these two subspecies, have been obtained. These individuals are also
referred to _Z. t. trinotatus_ on the basis of cranial features and
color.
_Specimens examined._--Total, 42, all from California, distributed as
follows: _Humboldt Co._: Trinidad, 4 (SDM); Carsons Camp, Mad River, 3
(USBS); 3 mi. W Arcata, 5 (MVZ); _7-3/10 mi. E Bayside_, 1 (MVZ); _12
mi. S Korbel, on Maple Creek_, 2 (MVZ); _Falk_, 1 (MVZ); Carlotta, 1
(MVZ); _F. B. Summer Redwoods, S Eureka_, 1 (MVZ); _Maple Creek, 1 mi. W
junction Mad River_, 12 (MVZ). _Mendocino County_: Mendocino City, 1
(MVZ); Albion River, 1/3 mi. E MacDonalds Ranch, 1 (MVZ); Russian Gulch
State Park, 10 (MVZ).
_Marginal records._--California: Trinidad; Russian Gulch State Park;
Albion River, 1/3 mi. E MacDonalds Ranch; Mendocino City; Carlotta.
=Zapus trinotatus montanus= Merriam
_Zapus trinotatus montanus_ Merriam, Proc. Biol. Soc. Washington,
11:104, April 26, 1897; Bailey, N. Amer. Fauna, 55:234,
August 29, 1936.
_Zapus montanus_, Preble, N. Amer. Fauna, 15:28, August 8, 1899.
_Type._--Female, adult, skin and skull; No. 79863, U. S. Nat. Mus.,
Biol. Surv. Coll.; Crater Lake, Klamath County, Oregon; obtained on
August 19, 1896, by Edward A. Preble, original No. 1388.
_Range._--From Crater Lake, Klamath County, Oregon, northward along the
Cascade Range into Hood River County, Oregon. Zonal range: Transition
and Canadian.
_Description._--Size medium; back near Ochraceous-Buff with admixture of
black hair, resulting in a grizzled, broad, dorsal band; sides lighter
than back, from near Ochraceous-Buff to near Pinkish-Cinnamon, and lined
with black hair; lateral line distinct; underparts usually pure white,
sometimes with slight suffusion of ochraceous on lower throat and upper
chest; tail bicolored, brown above and yellowish-white below; ears dark,
sometimes flecked with ochraceous, edged with yellowish-white; feet
grayish-white above; braincase relatively narrow; zygomata relatively
short; condylobasal length short; mastoid region relatively narrow;
palatal bridge short; auditory bullae large; frontal region inflated;
pterygoid fossae relatively narrow.
_Comparison._--From _Zapus trinotatus trinotatus_, _Z. t. montanus_
differs as follows: Size averaging smaller; sides more ochraceous, fewer
black hairs; upper parts duller; skull smaller; zygomatic arch shorter,
braincase relatively narrower; frontal region more inflated; pterygoid
fossae relatively narrower; zygomata narrower.
_Remarks._--The systematic status of _Z. t. montanus_ has been in doubt.
Several workers, for example, Howell (1920:227) and Preble (1899:28),
considered it to be a species, and others (Merriam, 1897a:104, Bailey,
1936:234) considered it to be a subspecies of _Z. trinotatus_. _Z.
montanus_ is here considered to be a subspecies of _Z. trinotatus_,
because of the agreement of the two in size and shape of the baculum,
diameter and pigment pattern of the hair, and the over-all proportions
of the skull. In addition, animals from intermediate geographic areas
are available and show actual intergradation.
Intergradation has been noted in specimens from North Santiam River,
3400 ft., Oregon. In color, in length of incisive foramina, in breadth
of braincase, and in width of zygomata these specimens are intermediate
between _Zapus trinotatus montanus_ and _Z. t. trinotatus_, but in the
sum-total of characters they are referable to the former. Specimens from
Lost Creek R. S., 10 mi. SE McKenzie Bridge, are intermediate in color
between _Z. t. trinotatus_ and _Z. t. montanus_; they are referable to
_Z. t. montanus_. The animals available from Brooks Meadow, 4300 ft., 9
mi. ENE Mt. Hood and the one from Mt. Hood, in color, in length of
incisive foramina, and in mastoid width, closely approach _Z. t.
trinotatus_ from Skamania County, Washington, but in the sum-total of
characters are nearest _Z. t. montanus_ and are here referred to
_montanus_.
_Specimens examined._--Total, 35, all from Oregon, distributed as
follows: _Deschutes County_: Tumalo Creek, 15 mi. W Bend, 6100 ft., 3
(MVZ). _Douglas Co._: Diamond Lake, 1 (USBS). _Hood River Co._: Brooks
Meadow, 4300 ft., 9 mi. ENE Mt. Hood, 10 (MVZ); _Mt. Hood_, 1 (USBS).
_Klamath Co._: _Crater Lake_, 3 (MVZ); _1/2 mi. N Government Camp, 6700
ft., Munson Valley, Crater Lake Nat'l Park_, 2 (MVZ); east slope Cascade
Divide, 6400 ft., Crater Lake Nat'l Park, 2; Anna Creek, Mt. Mazama,
6000 ft., 2 (USBS). _Lane Co._: Lost Creek R. S., 10 mi. SE McKenzie
Bridge, 6 (USBS); _Three Sisters, Alder Springs, 4300 ft._, 2 (USBS).
_Linn County_: North Santiam River, 3400 ft., 3 (MVZ).
_Marginal records._--Oregon: Brooks Meadow, 4300 ft., 9 mi. ENE Mt.
Hood; Tumalo Creek, 15 mi. W Bend, 6100 ft.; Anna Creek, Mt. Mazama,
6000 ft.; east slope Cascade Divide, 6400 ft., Crater Lake Nat'l Park;
Diamond Lake; North Santiam River, 3400 ft.
=Zapus trinotatus orarius= Preble
_Zapus orarius_ Preble, N. Amer. Fauna, 15:29, August 8, 1899.
_Zapus pacificus_ Merriam, Proc. Biol. Soc. Washington, 11:104,
April 26, 1897 (part--the part from Point Reyes, Marin County,
California).
_Zapus trinotatus orarius_, Hooper, Miscl. Publ. Mus. Zool. Univ.
Michigan, 59:67, January 12, 1944.
_Type._--Male, adult, skin and skull, No. 250, collection of E. A. and
O. Bangs (now in Mus. Comp. Zool.); Point Reyes, Marin County,
California; obtained on May 14, 1893, by C. A. Allen, original No. 618.
_Range._--Southern and western Marin County, California. Zonal range:
Upper Sonoran areas that are moist yet safe from continuous inundation.
_Description._--Size small; back dark ochraceous, usually overlaid with
black hairs forming broad dorsal band; side lighter than back with
admixture of black hairs; lateral line distinct, usually bright, near
Ochraceous-Buff; under parts strongly suffused with ochraceous; tail
bicolored, white to yellowish-white below and dark brown above; feet
grayish-white above; ears dark, edged with yellowish-white or tan; skull
small; zygomata narrow; braincase narrow; maxillary tooth-rows short;
interorbital region narrow; incisive foramina short; palatal bridge
relatively long; mastoid region relatively broad; occipitonasal length
short.
_Comparison._--From _Zapus trinotatus eureka_, _Z. t. orarius_ differs
in: Size smaller; color, dorsally and laterally, brighter, more
ochraceous; skull averaging smaller in all measurements taken except
length of palatal bridge, where it averages longer; auditory bullae
smaller, less inflated; pterygoid fossae narrower.
_Remarks._--Preble (1899:30) named this jumping mouse as a full species.
Included in the specimens examined were animals from Eureka and Mad
River, Humboldt County, California. Howell (1920:231) retained _Z.
orarius_ as a full species but restricted its range to Marin County,
California, and referred material from northern California, including
the animals from Eureka and Mad River, to a new subspecies (_eureka_) of
the species _Z. trinotatus_. Howell (_loc. cit._) suggested that _Z.
orarius_ had its closest affinity with _Z. t. eureka_ but remarked that
intergrading material was not available. Hooper (1944:68) arranged _Z.
orarius_ as a subspecies of _Z. trinotatus_ and suggested that
intergrades could be expected from geographically intermediate areas,
for example, northern Sonoma County, California.
Although animals from intermediate geographic areas still are not
available to show actual intergradation, I concur with Hooper (_loc.
cit._) and arrange _Z. orarius_ as a subspecies of _Z. trinotatus_. The
close relationship of _Z. orarius_ to _Z. trinotatus_ is evident;
certain diagnostic characters, held in common, are the shape and size of
the os penis, the diameter and pigment pattern of the hair, and the
general configuration of the skull.
Interbreeding in the wild between _Z. t. orarius_ and _Z. t. eureka_
probably does not take place, because these subspecies are separated by
terrain unsuited to jumping mice.
_Specimens examined._--Total, 29, all from California, distributed as
follows: _Marin County_ (MVZ): 3 mi. W Inverness, 300 ft., 14; _5 mi.
NNE Point Reyes Lighthouse_, 12; _W end Elk Valley, 10 ft._, 1; West
Portal, Fort Barry, 2.
_Marginal records._--California: 3 mi. W Inverness, 300 ft.; West
Portal, Fort Barry.
=Zapus trinotatus trinotatus= Rhoads
_Zapus trinotatus Rhoads_, Proc. Acad. Nat. Sci. Philadelphia,
1894:42, January 15, 1895.
_Jaculus hudsonius_, Baird, Repts. Expl. and Surv. 111, 8 (pt. 1):
433, July 14, 1858 (part--the part from Washington).
_Zapus hudsonius_, Coues, Bull. U. S. Geol. and Geog. Surv. of the
Territories, 2nd ser., No. 5:260, 1877 (part--the part from
Steilacoom [Pierce County], Washington).
_Zapus imperator_ Elliot, Field Columbian Mus., publ. 30, zool.
ser., 1:228, February 1, 1899, type from Siegs Ranch, Elwah River,
Clallam County, Washington.
_Zapus princeps trinotatus_, Dalquest, Univ. Kansas Publ. Mus. Nat.
Hist., 2:371, April 9, 1948.
_Type._--Male, adult, skin and skull, No. 360, S. N. Rhoads Coll.; Lulu
Island, mouth of Frazer River, British Columbia; obtained on May 31,
1892, by S. N. Rhoads (type in Philadelphia Acad. Nat. Sci.).
_Range._--Pacific coastal region from Requa, Del Norte County,
California, north in Oregon west of the Cascades, and in Washington
including the Cascades; to southwestern British Columbia.
_Description._--Size large; back from near Ochraceous-Buff to near Tawny
with admixture of black hair forming broad dorsal band; sides lighter
than back from near Ochraceous-Buff to near Tawny; lateral line usually
distinct; belly white, sometimes with faint suffusion of ochraceous on
lower throat and upper chest; tail bicolored, brown above, white to
yellowish-white below; ears dark, sometimes flecked with color of sides,
edged with ochraceous; feet grayish-white above; palatal bridge
relatively short; incisive foramina relatively long; condylobasal region
long; zygomatic width great; braincase relatively broad; distance from
incisors to postpalatal notch relatively great.
_Comparisons._--For comparisons with _Zapus trinotatus montanus_ and
_Zapus trinotatus eureka_ see accounts of those subspecies.
_Remarks._--This subspecies retains most of its diagnostic characters
throughout nearly all parts of its geographic range. Intergradation
occurs between _Z. t. eureka_ and _Z. t. trinotatus_ in extreme
southwestern Oregon and northwestern California (see account of _Z. t.
eureka_). Intergrades between _Z. t. montanus_ and _Z. t. trinotatus_
have been commented on in the account of _Z. t. montanus_. Specimens
from Eugene, Oregon, according to Bailey (1936:232), show affinity to
_Z. t. montanus_ but are considered by him to be _Z. t. trinotatus_.
_Specimens examined._--Total, 238, distributed as follows:
BRITISH COLUMBIA: Alta Lake, on Pac. Gt. Eastern Ry., 2600 ft., 5 (MVZ);
Okanagan, 1 (FM); _Vedder Crossing_, 4 (1 MVZ, 3 PM); _Chilliwack
Valley_, 2 (NMC); 18 mi. S Chilliwack, 1 (MVZ); Cultus Lake, 2 (NMC);
_Lihumption Park, 4500-4800 ft._, 12 (NMC); _Seymour Mtn., 4000 ft._, 8
(1 MVZ, 7 PM); _Cariboo_, 2 (FM); _Sumas_, 8 (1 MVZ, 7 FM); Huntingdon,
40 (NMC); _Parnassus Creek, Black Tusk Meadow, 5200 ft._, 1 (PM); _Howe
Sound, Brackendale_, 2 (NMC); Stanley Park, Vancouver, 1 (PM); _Allison
Pass, Manning Park_, 1 (PM); Manning Park, 2 (PM).
CALIFORNIA: _Del Norte Co._: Crescent City, 11 (6 FM, 5 USBS); Requa, 4
(FM).
OREGON: _Benton County_: _3 mi. N Corvallis_, 2. _Clatsop County_: Old
Fort Clatsop, 100 ft., 11 (MVZ); 7-1/2 mi. S Cannon Beach, 50 ft., 1
(MVZ). _Columbia County_: 7 mi. SE Rainier, 100 ft., 11 (MVZ). _Curry
County_: Gold Beach, 3 (FM). _Douglas County_: Gardiner, 7 (5 MVZ, 2
FM). _Lane County_: Sutton Lake, 6 mi. N Florence, 1 (MVZ). _Lincoln
County_: _Delake_, 3 (2 MVZ); Newport, 2 (MVZ). _Multnomah County_:
Portland, Council Crest, 950 ft., 1 (MVZ). _Tillamook Co._:
_Tillamook_, 1 (MVZ); _9 mi. S Tillamook_, 1 (MVZ); Netarts, 3 (SDM);
Blaine, 3 (MVZ). _Washington County_: 18-1/2 mi. NW Portland, 1300 ft.,
5 (MVZ).
WASHINGTON: _Clallam County_: Deer Lake, 3800 ft., 3. _Clarke County_:
_3-1/2 mi. E and 1-1/2 N Amboy, 3500 ft._, 3 (MVZ); _1-1/2 mi. ENE
Amboy, 3500 ft._, 13 (MVZ); 3-1/2 mi. E and 5 mi. N Yacolt, 500 ft., 1
(MVZ); _1-1/2 mi. W Yacolt, 800 ft._, 11 (MVZ). _Cowlitz County_: _6 mi.
NE Kelso_, 4 (MVZ); _4 mi. E mouth Kalama River_, 5 (MVZ). _King
County_: Lakeridge Tract, S end Forest Ave., Lake Washington, 2 (MVZ);
Seattle 2 (MVZ); Snoqualmie Pass, 5 (MVZ). _Mason County_: Potlatch, 2
(MVZ). _Pacific County_: _1-1/2 mi. N Chinook, 10 ft._, 1 (MVZ); 3-1/2
mi. SE Chinook, 10 ft., 5 (MVZ). _Pierce Co._: 5 mi. E Tacoma, 4 (MVZ);
Puyallup, 3 (1 MVZ, 2 FM); Mt. Rainier, 1 (MVZ); 3 mi. E Ashford, 1
(LMH). _Skamania County_: Ice Caves, 2800 ft., 5 mi. WSW Guler, 1 (MVZ).
_Thurston County_: Boston Harbor, 5 (CAS). _Wahkiakum County_: 4 mi. E
Skamokawa, 5 (MVZ). _Whatcom County_: Baker Lake, 2 (MVZ).
_Marginal records._--British Columbia: Okanagan; Manning Park.
Washington: Baker Lake; Snoqualmie Pass; Mt. Rainier; Ice Caves, 2800
ft., 5 mi. WSW Gulch. Oregon: Portland, Council Crest, 950 ft.
California: Requa; Crescent City. Oregon: Gold Beach; Gardiner; Sutton
Lake, 6 mi. N Florence; Newport; Netarts; Old Fort Clatsop, 100 ft.
Washington: 3-1/2 mi. SE Chinook, 10 ft.; Deer Lake, 3800 ft. British
Columbia: Stanley Park, Vancouver; Alta Lake, 2600 ft.
=Zapus princeps= Allen
(Synonymy under subspecies)
_Range._--The Rocky Mountains region from Yukon south into Arizona and
New Mexico; westward through eastern Oregon and through the Cascades and
Sierra Nevada of California; eastward in the northern Great Plains to
extreme eastern parts of the Dakotas (see fig. 46).
_Characters of the species_: _External._--Size medium to large (total
length 216 mm to 247 mm); tail longer than head and body (129 mm to 148
mm) and bicolored, pale brown to grayish-brown above, white to
yellowish-white below; hind feet long (31 mm to 34 mm), grayish-white
above; back variable from yellowish-gray to salmon-brown and ochraceous;
sides paler than back; lateral line usually present but sometimes
indistinct or entirely absent (when present usually clear
Ochraceous-Buff); ventral coloration white, usually suffused with
ochraceous; ears usually dark, sometimes flecked and usually narrowly
edged with light color; guard hairs average 142 microns (130u to 168u)
in diameter; underhair with medullary pigment in form of hollow squares;
cuticular scales of underhair larger and fewer than in other species.
_Baculum._--Size medium (total length 5.6 mm to 6.6 mm); base moderately
broad (0.7 mm to 0.8 mm); tip narrow (0.26 mm to 0.31 mm) rounded and
dished out in dorsal aspect, blunted; shaft rounded, slightly
sinusoidal, recurved at tip.
_Skull._--Large, not exceptionally broad and deep in relation to length;
rostrum broad but tapering; pterygoid fossa moderately narrow; anterior
ramus of zygomatic process usually broad; incisive foramina usually
broadly rounded and elongate; auditory bullae usually moderately
inflated; coronoid process of mandible relatively short. Upper premolars
of medium size (averaging .55 mm in length and .50 mm in breadth),
sometimes functional, with occlusal surface normally divided by single
shallow re-entrant fold; m1 relatively short, narrow anteriorly.
[Illustration: FIG. 46. Distribution of _Zapus princeps_.
Guide to subspecies
1. _Z. p. cinereus_ 7. _Z. p. oregonus_
2. _Z. p. curtatus_ 8. _Z. p. pacificus_
3. _Z. p. idahoensis_ 9. _Z. p. princeps_
4. _Z. p. kootenayensis_ 10. _Z. p. saltator_
5. _Z. p. luteus_ 11. _Z. p. utahensis_
6. _Z. p. minor_]
GEOGRAPHIC VARIATION
There are 11 subspecies recognized, most of which are in the mountains
of the western United States and southwestern Canada. There is
geographic variation in color, relative proportions of external parts
(tail, hind feet, head, and body), and shape and size of the skull.
Three basic types of coloration occur in _Z. princeps_, as pointed out
by Hall (1931:9). Yellow-sided dark-backed jumping mice exemplified by
_kootenayensis_, _idahoensis_, and _utahensis_ are found to the eastward
in the Rocky Mountains. Reddishbrown-sided, brown-backed jumping mice
typified by _luteus_ and _pacificus_ are found to the westward in the
Sierra Nevada and in New Mexico and Arizona; mice with yellowish-buff or
pinkish-buff-sides and light backs are the subspecies, _cinereus_,
_curtatus_, and _oregonus_, that occur in the intervening Great Basin.
External dimension as a whole decreases from north to south, although
not uniformly. For example, the smallest individuals are of the
southernmost geographic subspecies (_Z. p. luteus_), but the largest are
of the subspecies (_Z. p. utahensis_) that is near the geographic center
of the range for the species. In the skull there is geographic variation
in the length and shape of the zygomata, size and shape of the incisive
foramina, alignment of maxillary tooth-rows, size and shape of auditory
bullae, position of the postpalatal notch in relation to M3, and the
presence or absence and size of the medial projection on the inferior
ramus of the zygomatic process of the maxillary.
NATURAL HISTORY
_Habitat._--_Zapus princeps_ occurs most commonly adjacent to streams
where grasses and herbs are in lush growth. It frequents mountain
meadows neighboring small streams and is often taken from alder, aspen,
or stands of willow, where the moist ground supports a heavy undergrowth
of herbs. Davis (1939:330) found these mice in heavy herbage along a
small stream bordered by quaking aspen near Victor, Teton County, Idaho.
They were found along streams bordered by willow, rose, alder,
huckleberry, sedges, and herbs of various kinds at Alturas Lake, Mill
Creek, and at the head of the Pahsimeroi River. Linsdale (1938:195)
found jumping mice in the Toyabe Mountains, Nevada, near the streamsides
or in seepy areas close to the streams where associated vegetation
included rose, willow, wild peach, sage, grasses, and herbs. In the
Uinta Mountains, Utah, R. D. Svihla (1931:264) obtained them from
willows along streams in mountain parks. Borell and Ellis (1934:37) in
the Ruby Mountains, Nevada, found jumping mice to be common in heavy
vegetation along streams. Louise Kellogg (1916:369) obtained jumping
mice in northern California; all were near water, in grassy meadows, or
under alders where vegetation was dense.
_Zapus princeps_ is locally abundant, but its numbers seem to vary
considerably from year to year as well as seasonally. Early autumn, when
young of the year are abroad, seems to be the period of greatest
abundance. Moore (1928:154) remarks that runways were plainly marked and
well strewn with four-inch pieces of brome-grass. Davis (1939:334) notes
that _Z. princeps_ has runways, and found that sections, four inches
long, of cut grass piled in runways was good evidence of the presence of
the mouse.
_Behavior._--In reference to locomotion of _Z. princeps_, Davis (_loc.
cit._) writes, "In rapid progression jumping mice move by a series of
zigzag hops. One young of the year found in tall grass near Victor made
horizontal leaps of approximately three feet. The zigzag course was
difficult for me to follow, and I was led to wonder if this mode of
locomotion were not advantageous to the mice in eluding animals that
would do them harm." Hollister (1912:26) remarked that _princeps_, when
startled, sometimes jumps five to six feet at a bound. Concerning the
swimming ability of _Z. princeps_, Bailey (1936:233) quotes from
Hollister's notes, "While I was walking around the grassy border of a
small pond one jumped out at my feet and struck in the water like a
frog, which at first it was thought to be, until it was seen swimming
across the pond on the surface of the water ... he certainly handled
himself as if perfectly at home and swam with little effort and great
speed over the still surface of the pond." Davis (1939:334) obtained two
individuals at Mill Creek, Idaho, in traps placed on artificial islands
of stones in the middle of the creek where the water was about six
inches deep. He speculated that the only way the mice could have reached
the traps was by swimming. Grinnell, Dixon, and Linsdale (1930:531)
record an individual which was seen hopping in the inch-deep water of a
small stream at Lake Helen, California.
According to Hollister (1912:26) and Davis (1939:335), jumping mice are
for the most part nocturnal, but occasionally they are seen by day in
tall grass.
Little is recorded concerning the hibernation of _Z. princeps_. What
data are available suggest that, starting in July, these animals
accumulate a heavy layer of fat on the inside of the skin with
especially large amounts in the inguinal region. By August or early
September, animals are excessively fat, and the start of hibernation is
dependent then upon the arrival of a heavy cold snap. Grinnell, Dixon,
and Linsdale (1930:531), in their study of the vertebrates of the Lassen
Peak region of California noted that the latest activity by these mice
was September 13. As regards the time of onset of hibernation in Idaho,
Davis (1939:336) states that, "I know of no records of capture later
than September and infer that hibernation begins in that month or the
next." Bailey (1932:227) writes that in New Mexico, animals obtained on
September 20 were very fat, probably were ready to hibernate at the
first cold wave, and had winter nests in burrows well underground.
_Enemies._--Bailey (_loc. cit._) lists hawks, owls, and weasels as
natural predators on _Z. princeps_. Stanford (1931:362) records the
garter snake (_Thamnophis_) as a predator of jumping mice. A large snake
of this genus obtained by him regurgitated two jumping mice a few hours
after its capture. Grinnell, Dixon, and Linsdale (1937:232) report that
on Parker Creek, in California, H. C. Bryant frightened a weasel that
dropped a freshly killed jumping mouse. Crowe (1943:407) reported
_Cuterebra_ fly larvae in the inguinal region of a _Z. princeps_
obtained at Invermere, British Columbia. Several mice of this species
taken at Moccasin Lake, 19 mi. W and 4 mi. N of Lander, 10,000 ft.,
Fremont County, Wyoming, were heavily infested with mites of the family
Laelaptidae.
_Food._--In early September in central Utah, Moore (1928:154) found only
a white, starchy, glutinous paste in stomachs of six _Z. princeps_ and
only traces of a brown seed coat in a seventh. The main seeds eaten
seemed to be from an introduced brome-grass which was abundant in the
vicinity of capture. Bailey (1932:226) wrote of _Z. princeps_ in New
Mexico, that "In feeding they cut down the tall grass, beginning at the
bottom and cutting the stem at intervals as high as they can reach until
the seed part of the grass is brought down." He (_op. cit._:227)
remarked that the food was almost entirely seeds of grass and grasslike
plants and that the stomach contents almost always were perfectly clean
white dough from the shelled kernels of small seeds.
_Reproduction._--Females with embryos have been collected from late May
to mid-July and lactating individuals until late August. Possibly there
is only one litter per season as Davis (1939:336) suggests is the case
in Idaho.
Embryos in 25 pregnant females averaged 5 (2-7). The mammae of the
female are arranged in four pairs (two abdominal, one pectoral, and one
inguinal).