Aulocara femoratum Scudder
Link directly to photos of adults, nymphs,
Distribution and Habitat
A. femoratum continental distribution map
Wyoming distribution map
The whitecrossed grasshopper is an inhabitant of western grasslands.
Although widely spread, its distribution includes only 60 percent of that
of its congener, the bigheaded grasshopper, Aulocara elliotti. The
whitecrossed grasshopper occurs most frequently in vegetation types of
the mixedgrass prairie in which the mid grasses, western wheatgrass and
needleandthread, are abundant as well as the short grass, blue grama. The
species also occurs in the bunchgrass, shortgrass, and desert prairies,
but no descriptions of specific habitats in these prairies have been published.
Because the whitecrossed grasshopper feeds on valuable forage grasses and
increases to high densities in certain habitats of the mixedgrass prairie,
it is occasionally an important pest species. It is usually a subdominant
member of an outbreak assemblage in which A. elliotti is often the
dominant species, but it may also become the dominant species with densities
as high as 13 adults per square yard. The whitecrossed grasshopper is slightly
smaller than A. elliotti. Live weight of males from the mixedgrass
prairie of eastern Wyoming averages 141 mg and females 460 mg (average
dry weight of males 42 mg, females 137 mg). It is a less injurious species
than A. elliotti because of its smaller size, lower densities, less
frequent occurrence, and thriftier feeding habits (i.e., little clipping
of grass leaves).
The whitecrossed grasshopper is a general grass feeder. Examination of
crop contents of late instars and adults inhabiting a site in the mixedgrass
prairie of eastern Wyoming revealed that all eight species of the perennial
grasses and sedges growing at the site had been exploited for food (Table
1). Only the senescent annual grasses, such as downy brome, were lacking
in the crop contents. The greatest utilization was made of western wheatgrass
and needleleaf sedge. This study also revealed a remarkable difference
in the diets of adult males and females. The males ingested much larger
amounts of short grasses and sedge, while the females ingested more of
the mid grasses. These results appear to be due to differences in behavior.
The males walk extensively on the ground, presumably to find and court
females, and thereby make contact with short grasses more often than the
females, which are more sedentary and usually climb mid grasses close by
in order to feed.
The majority of crops contained two to three species of grasses and
sedge, but a relatively large number contained only one species. Of 22
male crops, nine were found to contain only sedge and one only western
wheatgrass. Of 16 female crops, five were found to contain only western
wheatgrass and one only sedge.
Examination of crop contents of the whitecrossed grasshopper collected
in desert prairie of southwest Texas revealed that buffalograss and blue
grama were the main host plants. Other grasses found in the crops were
burrograss, fall witchgrass, sideoats grama, hairy grama, and Sporobolus
Direct observations have been made of feeding by the late instars and
adults on several species of plants: western wheatgrass, needleandthread,
blue grama, prairie junegrass, and needleleaf sedge. The usual method of
attack is for grasshoppers to climb a mid grass, turn around head down,
and feed on an edge leaving a narrow opposite edge standing as they progress
toward the base. On blue grama they may turn around without climbing, because
of its shortness, and feed toward the leaf base. They may also feed from
a horizontal position on the grazed end of a leaf or stem, ingesting the
whole width as they consume it to the base. Infrequently, grasshoppers
have been observed to feed on dry fallen grass and on dry cow dung from
a horizontal position. The whitecrossed grasshopper feeds on bran bait.
Dispersal and Migration
In spite of their relatively short wings, whitecrossed grasshoppers have
the capacity to fly and disperse. In flushed flight they cover distances
of 2 to 6 feet at heights of 4 to 10 inches. The flight is silent and straight
with the grasshopper facing away from the intruder upon landing. Evidence
for dispersal is the discovery of an "accidental" in a mountain site (altitude
8,500 feet) approximately 10 miles west of the closest resident site (altitude
5,450 feet) near Boulder, Colorado.
The whitecrossed grasshopper (Fig. 6 and 7)
is a medium-sized species with a general appearance similar to A. elliotti.
The head is noticeably large; most individuals have a dark vertical streak
above the front articulation of the mandible (short distance below the
compound eye). The disk of the pronotum is dark and marked by light lines
forming an X-like figure.
The wings usually do not reach the end of the abdomen; rare individuals
have wings that extend past the abdomen. The posterior margin of the eighth
abdominal sternum of the females has two deep clefts (Fig.
9), which is easily distinguishable from
the eighth abdominal sternum of Aulocara elliotti. The hind femur
is cream and conspicuously marked by three dark bands; the hind tibia is
The nymphs (Fig. 1-5) are identifiable by
their color patterns, structures, and shape.
1. Head with face moderately slanting; lateral foveolae quadrilateral,
visible from above; antennae filiform; dorsum of head light tan, with fuscous
middle band divided by narrow light tan stripe.
2. Pronotum with disk chiefly solid light tan in instars I to III, X-figure
visible and fuscous triangle on each side of posterior area of disk in
instars IV and V; lateral lobes fuscous dorsally and light tan or cream
ventrally (Fig. 5).
3. Hind femur with fuscous dorsal stripe entire in instars I to III;
broken or interrupted by light patches in instars IV and V; hind tibia
of instars I and II two-toned gray, of instars III to V light blue.
4. Top of abdomen with light tan band continuing from disk of pronotum.
Posterior margin of eighth abdominal sternum cleft in female instars IV
and V, nearly as clear as in the adult female (Fig.
5. General body color light tan or cream with highly contrasting fuscous
Compared with nymphs of A. elliotti,
the nymphs of the whitecrossed grasshopper are lighter colored with greater
contrast between the background color and the fuscous markings. Nymphs
of A. elliotti are mainly drab gray, which renders fuscous markings
The whitecrossed grasshopper is an intermediate-hatching species. Emergence
of first instars occurs 10 to 14 days after the appearance of A. elliotti
in the habitat. In the mixedgrass prairie of Montana and Wyoming, hatching
normally begins during the first week of June. The cause of the later hatch
is due, at least partly, to the greater depth of whitecrossed grasshopper
eggs in the soil relative to those of A. elliotti.
The nymphs emerge over a period of two weeks. They normally have plenty
of green grasses available for food, and warm weather predominates during
their development. The males have four nymphal instars and take a minimum
of 30 days to become adults, while the females have five nymphal instars
and take a minimum of 42 days to become adults. Because the sizes at which
males and females start out the nymphal stage are the same, the females
require more developmental time and an additional instar to reach the female
adult size, which is over threefold that of the male.
Adults and Reproduction
The adults remain in the same habitat in which the eggs hatched and the
nymphs developed. In the mixedgrass prairie of Montana and Wyoming, the
adult stage is reached during the first and second weeks of July. The males
fledge first, and then the females. Upon maturing, the adults begin to
mate and reproduce. Weekly observations in a mixedgrass prairie site (Goshen
County, Wyoming T20N R60W Sec 3 NE) indicated that mating began three weeks
after the fledging of females. During the morning hours the males chase
after females, courting those that stop or are sitting quietly. The males
court by movements of the hindlegs that resemble stridulation. Although
sounds of stridulation have not been heard by human observers, female grasshoppers,
which are within 2 inches of the source, may hear courtship signals or
may visually detect movement of the hindlegs. No observation of successful
engagement of the genitalia has been made. Pairs in copulo, however, have
been seen during the morning as early as 10:30 a.m. and as late as 1:30
p.m., and attempts by the males to mate have been observed as late as 5:30
p.m. DST. For oviposition, a female selects a small (1 to 6 square inches),
secluded, bare area surrounded by blue grama or other short grass, and
faces into one of the plants. One observation of the entire process of
oviposition, which took one hour, was made in a laboratory terrarium. The
female selected bare ground and worked her abdomen into the soil to a depth
of three-quarters inch. After extracting her ovipositor, she spent two
minutes brushing soil and litter over the hole with her hind tarsi, and
then she walked away. In nature, pods lie in the soil with the long axis
oriented vertically and are inserted one-eighth inch below the ground surface
and to a depth of three-quarters inch. The pods are nine-sixteenths to
ten-sixteenths inch long and one-quarter inch in diameter (Fig.
10). The walls are unusually strong and thick. The cap is without a
nipple (present in pods of A. elliotti). The egg mass, numbering
9 to 11 eggs, rests in the bottom half of the pod. The eggs are pale yellow
and 4.7 to 5.2 mm long.
Overwintering of the species occurs in the egg stage; there is probably
one generation annually. The fecundity of the whitecrossed grasshopper
has not been studied.
In the mixedgrass prairie, the whitecrossed grasshopper inhabits the more
luxuriant vegetation types where there is a greater abundance of mid grasses
such as western wheatgrass and needleandthread in addition to the dominant
short grass, blue grama. Often associated with A. elliotti or Metator
pardalinus, it is usually a subdominant member of a diverse assemblage
of grasshoppers. As a subdominant it ranges in density from 0.1 to 2 adults
per square yard. It occasionally becomes the dominant species in Montana
and Wyoming, ranging from 8 to 13 adults per square yard in assemblages
of 20 to 25 per square yard. In a mixedgrass prairie site near Edgemont,
South Dakota the species built up high numbers, reaching estimated densities
of 10.5 late nymphs and adults per square yard in an assemblage of 21 grasshoppers
per square yard.
It is of less frequent occurrence in mixedgrass prairie sites than A.
elliotti. Of 278 sites surveyed in the mixedgrass prairie of Wyoming
in 1990, five sites were inhabited by A. femoratum and 86 sites
by A. elliotti. In 1991, of 419 sites surveyed, four sites were
inhabited by A. femoratum and 47 sites by A. elliotti. The
species appears to be more prevalent in Montana than in Wyoming. Of 38
study sites in the mixedgrass prairie of Montana, it inhabited nine sites
and was dominant in two of these.
A three-year study (1949-51) of rangeland grasshopper populations in
Montana revealed that the whitecrossed grasshopper can increase from low
to high densities in one year, and then fall as suddenly the next year.
The whitecrossed grasshopper is a geophilous insect spending most of the
day and all of the night on the ground. At night both nymphs and adults
rest on bare areas of 1 to 10 square inches interspersed among the grassy
vegetation. They do not seek shelter under a canopy of vegetation, but
are surrounded closely by the dominant short grasses and sedges. Environmental
temperatures decline during the night and by early morning, before sunrise,
reach lows around 60°F. Under these relatively cold conditions, the
grasshoppers are immobile. About two hours after sunrise when the rays
of the sun strike the grasshoppers on the ground, they stir and turn a
side perpendicular to the rays and usually lower the associated hindleg
to expose the abdomen. During this period they are mainly quiescent, but
occasionally they walk to another location, turn around to expose the other
side, or they may preen their antennae or compound eyes with the front
tarsi. During the basking period, soil surface temperatures range from
60° to 90°F and air temperatures at the 1-inch level from 61°
to 82°F. After their body temperatures rise to some preferred level,
they become active and begin to walk, feed, court, and mate. The morning
period of activity lasts for about two hours. Increasing temperatures cause
activities to slow down and finally the grasshoppers are compelled to take
protective measures. Several behavioral responses keep their body temperatures
within tolerable levels. First, they may "stilt," raising up on their legs
to hold their bodies off the hot soil surface. They may use all three pairs
of legs, or they may use only the first two and raise the flexed hindlegs
from contact with the soil. As temperatures rise still further, they may
crawl onto a short grass or sedge and rest diagonally facing the sun. In
this position they expose the least body surface to the rays of the sun
and are 1 inch above the ground and away from hot, bare areas. They also
may climb stems of mid grasses, such as western wheatgrass, to heights
of 2 to 7 inches. Less often, they crawl into the shade of vegetation.
When temperatures decline in the afternoon, the grasshoppers again become
active and when temperatures drop further, they bask. Finally, as the sun
begins to set and shadows engulf the habitat, the grasshoppers take their
nighttime positions on the ground or litter.
Alexander, G. and J. R. Hilliard, Jr. 1969. Altitudinal and seasonal distribution
of Orthoptera in the Rocky Mountains of northern Colorado. Ecol. Monogr.
Anderson, N. L. 1973. The vegetation of rangeland sites associated with
some grasshopper studies in Montana. Montana Agr. Exp. Stn. Bull. 668.
Anderson, N. L. and J. C. Wright. 1952. Grasshopper investigations on
Montana range lands. Montana Agr. Exp. Stn. Bull. 486.
Fry, B., A. Joern and P. L. Parker. 1978. Grasshopper food web analysis:
use of carbon isotope ratios to examine feeding relationships among terrestrial
herbivores. Ecology 59: 498-506.
Larsen, J. C., J. A. Hutchason, and T. McNary. 1988. The Wyoming Grasshopper
Information System. Cooperative Agricultural Pest Survey, University of
Otte, D. 1970. A comparative study of communicative behavior in grasshoppers.
Univ. Michigan Mus. Zool. Misc. Publ. 141.
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