Phoetaliotes nebrascensis (Thomas)
Wyoming Agricultural Experiment Station Bulletin 912
Species Fact Sheet
by Robert E. Pfadt
Geographic range of Phoetaliotes
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The largeheaded grasshopper ranges widely in the grasslands of North
America. Preferring a habitat of tall, lush grasses, it is often the
dominant grasshopper species in the tallgrass prairie and is a common
inhabitant in taller types of the mixedgrass prairie. In shorter types
it may be locally abundant in patches of tall grass growing in swales,
ravines, along streams, and in roadsides.
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Feeding mainly on grasses, the largeheaded grass-hopper adds to
the damage caused by infestations of rangeland grasshoppers. In
the lush, tallgrass prairie, damage is visible but of little economic
importance. Measurements of damage have not been successful in showing
any statistical significance between treated and control plots.
In the mixedgrass prairie, this grasshopper congregates in swales,
especially during droughts, and consumes much of the forage that
is in short supply for livestock and wildlife. In fall, adults may
invade fields of winter wheat and feed on the seedlings, consuming
the entire plant to ground level.
The female weighs twice as much as the male. Live weights of males
collected from the mixedgrass prairie of southeastern Wyoming averaged
206 mg and females averaged 419 mg (dry weights: males 63 mg, females
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The largeheaded grasshopper feeds almost exclusively on grasses,
an unusual habit for a spurthroated grasshopper. It feeds heavily
on little bluestem, big bluestem, and Kentucky bluegrass in the
tallgrass prairie, while in the mixedgrass prairie it feeds principally
on western wheatgrass. Populations in the bunchgrass prairie of
west-central Idaho feed on bluebunch wheatgrass, but in its absence
they feed on sand dropseed.
Extensive laboratory feeding tests reveal that largeheaded grasshoppers
surprisingly prefer several species of grasses and forbs to their
usual host plants. The preferred plants in the laboratory include
the grasses: downy brome, Scribner panicum, barnyardgrass, witchgrass,
junegrass, and foxtail barley; and the forbs: dandelion, meadow
salsify, and skeletonweed. Plants as acceptable as the natural host
plants include green bristlegrass and smooth brome, both introduced
species. Smooth brome grows profusely in roadsides and often harbors
dense populations of the largeheaded grasshopper. Less attractive
grasses include blue grama, buffalograss, sand dropseed, needleandthread,
prairie sandreed, and Kentucky bluegrass. The latter grass, however,
is ingested in considerable amounts when it occurs in the habitat.
In tall, lush grasses, the largeheaded grasshopper rests vertically
head-up on the host plant. During feeding, it may remain in this
position or it may turn around and face vertically head-down. In
either orientation it eats the edge of the leaf, creating a long
gouge along one side and leaving a narrow edge of the leaf intact.
The feeding of a nymph (instar IV) on western wheatgrass resulted
in a 30 mm long, 2 mm wide gouge in the middle of the leaf, with
1 mm wide edge left standing. As soon as a head-down individual
finishes a feeding bout, it turns around and again rests vertically
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Because the majority of adults of the largeheaded grasshopper develop
short wings unsuited for flying, this form of the species cannot
disperse or migrate very far. When the need arises, however, adults
readily disperse within the locale of their habitats. On Montana
rangeland in midsummer, they have been observed to move from drying
vegetation to nearby green vegetation. When these green areas became
dry, they moved to adjacent gullies where the grasses still remained
green. In southeastern Wyoming short-winged adults moved from a
draw that had dried out in October to nearby seedling winter wheat,
a distance of 30 to 90 feet. A mark-and-recapture study of movement
of short-winged adults in the Nebraska sand prairie indicated a
net displacement of individuals 3 to 13 feet from one day to the
next. The distance for an individual (a male) with the longest period
between marking and recapture (14 days) amounted to 135 feet.
The less common long-winged adults have strong powers of flight
and no doubt are able to disperse considerable distances. Perhaps
during past times, development of large numbers of long-winged adults
with subsequent dispersal resulted in the widespread geographic
range of this species.
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Figures 1-5. Appearance
of the nymphal instars, their sizes, structures, and color
patterns. Notice progressive development of wing pads. BL=body
length, FL=Hind Femur Length. AS=number of antennal segments
First Instar: BL 2.3-4.6 mm FL 2.1-2.4 mm AS 13.
Second Instar: BL 6.3-7.1 mm FL 3.3-3.6 mm AS 16.
Third Instar: BL 7.9-10.7 mm FL 4.6-6.8 mm AS
Fourth Instar: BL 12-13.5 mm FL 6.5-8.7 mm AS 21-23.
Fifth Instar: Males: BL 13.7-15.2 mm FL 8.7-9.9
mm AS 23-25.
Figures 6-10. Appearance
of the adult male and female, wings, cercus, and egg pod.
Adult Male: BL 17.8-19.4 mm FL 10.6-11.4 mm
Adult Female: BL 20.5-22.5 mm FL 12.1-13.1 mm AS
Fig. 8, The wings
of a long-winged female.
Fig. 9, End of male
abdomen showing cercus, furcula, and
other structures of terminus.
Fig. 10, Egg pod and
several loose eggs.
The largeheaded grasshopper, slim and medium-sized, possesses a
very large head relative to the rest of the body. The face is slanted.
Most adults have short wings that extend only to the second or third
abdominal segment and end in a point (Fig. 6 and 7). The rarer long-winged
individuals (0.5 to 5.5 percent in a population) have wings extending
a few millimeters beyond the end of the abdomen. Infrequently, as
much as 25 percent of a population is long-winged. The body color
of live adults is primarily light gray, the venter is often yellow.
Dried specimens usually turn tan. The dorsal stripe of the hind
femur is brown or fuscous and invades the lower medial area. The
hind tibia is blue. The male cercus is triangular, ending in a blunt
point (Fig. 9).
The nymphs are distinguishable by their structure, color, and shape
- The head is large relative to the rest of the body, face is
slanted; antennae are filiform; fuscous vertical stripe below
and horizontal stripe behind compound eye, both stripes contrasting
noticeably with light gray of head; compound eye brown with white
to pale tan spots.
- Edge of pronotal disk with fuscous wedge-shaped stripe, wide
anteriorly, narrowing posteriorly, faint in instar I.
- Hind femur with pronounced dorsal stripe that extends into ventral
half of medial area; hind tibia pale yellow with front fuscous
in instars I to III, blue in instars IV and V.
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Hatching about one month after Ageneotettix deorum, the
largeheaded grasshopper belongs to the late-developing group of
species. In the tallgrass prairie of eastern Kansas, eggs may begin
to hatch as early as May 22. In the mixedgrass prairie of southeastern
Montana hatching begins as early as June 8 and in southeastern Wyoming
as early as June 13. Hatching continues for a period of four weeks
or longer. Possible abiotic reasons for the late hatch include the
relatively deep location of the eggs in the soil (an inch or more)
and the cool soil temperatures of the lush habitat. In newly burned
tallgrass prairie, eggs hatch two weeks earlier than in unburned
tallgrass prairie due to the exposed soil warming more quickly in
the spring than soil covered by deep litter of the unburned prairie.
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The nymphs of the largeheaded grasshopper develop slowly. As measured
by the time from first appearance of instar I to the first appearance
of the adult, the nymphal period requires 55 days both in Kansas
and Wyoming. The probable cause of this extended period is the habitual
perching of nymphs on tall grasses. This location is usually several
degrees cooler than the ground location of most rangeland species.
Development of both males and females requires five instars for
completion of the nymphal period.
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Short-winged adults remain in the same general area in which the
nymphs developed, but do move short distances to track greener and
more nutritious host plants. The first adults appear in mid to late
July in Kansas, while in southeastern Wyoming they appear during
the first week of August.
Little is known about the maturation and reproduction of this grasshopper
in nature. Laboratory cage tests suggest a high rate of fecundity.
Short-winged females produced 120 eggs per capita during a reproductive
period experimentally set at 25 days. Long-winged females produced
fewer eggs because of the apparent necessity to divert part of the
nutrient intake to the production of flight muscles and long wings.
No observations of courtship have been made, and published observations
of mating are zilch. One mating pair was seen in the mixedgrass
prairie of eastern Wyoming at 9:15 a.m. DST on 1 August 1968 and
another in a roadside habitat dominated by smooth brome and western
wheatgrass at 9:30 a.m. DST on 26 August 1993. In the latter case,
the pair, which was basking vertically head-up 6 inches high on
a smooth brome leaf, had assumed the usual mating position of grasshoppers
(i.e., the male clinging on top of the female). The male's
head rested immediately behind and above the female's. Because of
the smaller size of the male, the female's genitalia had to curve
up to meet the male's curving down.
The oviposition sites selected by females are uncertain. In a published
study of grasshopper biology conducted in the sand prairie of southeastern
North Dakota, females were said to oviposit in vegetated sites.
However, it is not clear whether the females oviposited into or
close to crowns or into small bare areas interspersed among the
plants. The egg-laying behavior of females confined in a laboratory
terrarium of sandy loam soil and mixedgrass prairie turf further
confuses the issue. During ten days of confinement, five short-winged
females deposited five pods in the bare soil and none in the turf.
The pods are 1 to 1 1/4 inches long and slightly curved in the
region of the eggs (Fig. 10). The pods of short-winged females usually
contain 28 eggs, equaling the total number of ovarioles, while the
pods of long-winged females usually contain from 20 to 24 eggs.
Eggs range in color from olive to brownish yellow and measure from
4.1 to 4.4 mm in length.
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Populations of the largeheaded grasshopper reach their highest
densities in habitats of lush tall grasses. In the Flint Hills,
a tallgrass prairie region of eastern Kansas extending into Oklahoma
and Nebraska, the species is common and often dominant. This large
natural grassland, over 200 miles long from the north to the south
and as much as 50 miles wide, appears to be the species center of
distribution. Densities regularly number three to four young adults
per square yard and probably increase to much higher densities during
The distribution of the largeheaded grasshopper extends west into
the mixedgrass prairie, where the species occupies the more luxuriant
aspects, particularly swales, riparian areas, and roadsides. In
these sites, stands of western wheatgrass grow tall and rank, providing
favorable habitats and an abundance of food. Populations aggregate
in these habitats reaching densities as high as 12 young adults
per square yard and often achieve dominance in the grasshopper assemblage.
In contrast, surrounding mixedgrass prairie usually harbors less
than one young adult per square yard, and the species occupies a
low rank in the assemblage.
This grasshopper inhabits other grasslands of the West, usually
in limited areas and at low densities. In the shortgrass prairie
the species is rarely a member of the grasshopper assemblage, but
in northwestern Texas it was a common species on rangeland in two
out of seven years (1966-72). The desert prairie does not often
harbor the largeheaded grasshopper, but south of Tucson in an ungrazed
sanctuary of the Audubon Society it inhabits level uplands covered
by luxuriant stands of blue grama, plains lovegrass, and wolftail
grass. Average seasonal densities from 1985 to 1989 ranged from
0.1 to 0.3 per square yard. In 1989, at 0.3 per square yard, the
largeheaded grasshopper became the dominant species in a low-density
assemblage of nine species. This grasshopper is rarely found in
sites of the bunchgrass prairie, but in Idaho it is one of the major
species living on steep hillsides vegetated with bluebunch wheatgrass.
Densities, however, are low, usually less than one per square yard.
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In its preferred habitat of tall grasses the largeheaded grasshopper
behaves as a phytophilous species, sitting on stems and
leaves for most of the day and night. Warm nights are spent resting
vertically, head-up on grass leaves and stems at heights of 6 to
12 inches. Cold nights are spent lower down on the grass or under
In the morning on a clear day, two to three hours after sunrise,
the nymphs and adults, resting vertically head-up on tall grasses,
begin to bask by turning a side perpendicular to the rays of the
sun and lowering the associated hindleg. This orientation raises
their body temperature, which has fallen during the night, to that
of the habitat, which in Wyoming ranges from 50 to 60½F. They remain
quietly basking, occasionally stirring, for two to three hours and
eventually become active in mid morning. Individuals in habitats
of short and mid grasses usually spend the night under litter. In
the morning they bask sitting horizontally on bare ground.
After basking, the grasshoppers infrequently move about on the
tall grasses by crawling or jumping from one plant to another. They
may also back down a grass stem or turn around and crawl head-down
to reach the ground. On the ground they crawl and hop intermittently,
moving a net distance of 15 feet in 30 minutes. Grasshoppers perched
on tall grass have been observed to feed from early morning to evening
(7 a.m. to 6 p.m. DST). More observations of feeding, however, have
been made from 9 to 11 a.m. DST than during any other two-hour period.
A second period of basking occurs in late afternoon. At this time
the grasshoppers bask for approximately two hours. Near sunset,
when shadows engulf their habitat, they take nighttime positions.
Those basking vertically head-up on tall grasses may remain there,
or back down several inches, while others may find shelter under
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Anderson, N. L. and J. C. Wright. 1952. Grasshopper
investigations on Montana rangelands. Montana Agr. Exp. Stn. Bull.
Banfill, J. C. and M. A. Brusven. 1973. Food habits
and ecology of grasshoppers in the Seven Devils Mountains and Salmon
River Breaks of Idaho. Melanderia 12: 1-21.
Bock, C. E. and J. H. Bock. 1991. Response of grasshoppers
(Orthoptera: Acrididae) to wildfire in a southeastern Arizona grassland.
Amer. Midl. Nat. 125: 162-167.
Evans, E. W. 1989. Interspecific interactions among
phytophagous insects of tallgrass prairie: an experimental
test. Ecology 70: 435-444.
Gaines, S. B. 1989. Experimental analyses of costs
and benefits of wing length polymorphism in grasshoppers. Ph.D.
Dissertation. University of Nebraska-Lincoln.
Mulkern, G. B. 1980. Population fluctuations and
competitive relationships of grasshopper species (Orthoptera: Acrididae).
Trans. Amer. Entomol. Soc. 106: 1-41.
Pruess, K. P. 1969. Food preference as a factor
in distribution and abundance of Phoetaliotes nebrascensis.
Annals Entomol. Soc. Amer. 62: 323-327.
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