Trimerotropis pallidipennis (Burmeister)
Wyoming Agricultural Experiment Station Bulletin 912
Species Fact Sheet
by Robert E. Pfadt
Geographic range of
Trimerotropis pallidipennis (Burmeister)
The pallidwinged grasshopper, Trimerotropis
pallidipennis (Burmeister), ranges from southwestern Canada to Argentina,
making it the most widely distributed bandwinged grasshopper in the New World.
In North America the primary habitats of this grasshopper lie in the deserts of
the West where populations irrupt sporadically to damaging numbers. Vegetation
of habitats consists of shrubs, forbs, and grasses with a preponderance of bare
ground on which these grasshoppers commonly bask and rest. Outside their usual
rangeland habitats, pallidwinged grasshoppers find favorable environmental
conditions in weedy city lots.
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Importance Outbreak numbers of the pallidwinged grasshopper
damage the forage of their habitats. In Arizona in 1958 populations of nymphs
residing in low areas and along washes numbered from 50 to more than 100 per
square yard. They fed upon both annual grasses and forbs. Later in spring, the
late nymphs and adults migrated into irrigated crops. In small grains,
populations of 25 to 50 adults per square yard defoliated wheat and cut off
heads. In cotton fields, the grasshoppers numbered 5 to 10 per square yard and
consumed seedling plants to ground level. This damage compelled growers to
replant large acreages. Some growers found it necessary to replant twice
because of persistent grasshopper invasion. Other Arizona crops damaged in 1958
included carrots, sugarbeets, barley, milo, and corn. During outbreaks in
California, pallid winged grasshoppers have invaded and damaged fields of
safflower and grapes as well as cotton, sugarbeets, barley, and
Over a period of 29 years, 1952 to 1980, six outbreaks of the
pallidwinged grasshopper occurred in Arizona. These outbreaks have been brief,
one lasted two years and the other five lasted only one year. Similar short
outbreaks have occurred in the deserts of New Mexico, Utah, and
The most recent outbreak took place in west central Arizona
in 1998. During the night of April 19 swarms attracted to city lights landed
from Lake Havasu City to Bullhead City, a distance of approximately 50 miles.
Crushed by traffic on streets and highways, the grasshoppers caused cars and
trucks to skid and slide. Accumulations of the grasshoppers around buildings
reached a depth of 2 inches.
The pallidwinged grasshopper is a
relatively large rangeland grasshopper, but one that varies in weight depending
on environmental conditions of its habitat. Live weight of males collected in
the Sonoran Desert west of Phoenix, Arizona averaged 268 mg and females 565 mg
while males collected in a sagebrush habitat along a hillside above the
Gunnison River in Colorado (elevation 1,746 ft.) averaged 175 mg and females
429 mg. Live weight of six young males caught 14 May 2001 in the desert near
Mesa, Arizona averaged 261 mg and four immature females 399 mg (dry weight:
males 100 mg, females 145 mg).
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The pallidwinged grasshopper feeds on a variety of forbs and grasses. Daily
diets depend on availability and quality of food plants in the habitat. When
eggs hatch in early spring, annual grasses such as downy brome and needle grama
(Bouteloua aristioides), are lush and green and serve as the
chief food plants. Later in spring the annual grasses become dry and brown,
inducing the grasshoppers to switch to green perennial grasses and certain
A variety of diets has been revealed by several studies of
crop contents. In a four-year study, 1966-1969, in south-central Idaho,
examination of 153 crops of the pallidwinged grasshopper revealed that 63
percent of crops contained fragments of downy brome and 22 percent
tumblemustard. Other plants detected in the crops ranged from a trace to 11
percent. The grasses included crested wheatgrass, thickspike wheatgrass, and
Sandburg bluegrass. The forbs included milkvetch, western salsify, big
sagebrush, hoary aster, Greene rabbitbrush, and gray rabbitbrush. Also found in
crops were fragments of arthropod parts, fungi, and pollen.
analysis of adults collected in southwestern Texas near Alpine in the summer of
1974 showed that forbs were more frequently ingested (64 percent) than grasses
(36 percent). However, blue grama grass was the most often ingested single
plant, 23 percent, followed by a forb, Cryptantha sp, 16 percent. Other
grasses found in crops included Leptoloma cognata (7 percent) and
Setaria sp (1 percent); other forbs included Solanum sp (11
percent), Iva sp (10 percent), with smaller percentages of Croton
sp, Gaura sp, and Ratibida sp.
In the Sonoran Desert, 30
miles west of Tucson, Arizona, 68 of 126 crops (54 percent) contained needle
grama, six crops contained the forb Allionia incamata, four crops
contained the forb Franseria deltoidea, and three crops contained
Although these studies indicate a high degree of
polyphagy by the pallidwinged grasshopper, two-choice tests demonstrate that
the species has food preferences. Laboratory tests of 15 plant species offered
in pairs to adults collected in Millard County, Utah in 1998 revealed
preferences for dandelion, kochia, downy brome, crested wheatgrass, and
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Migration and Dispersal
The pallidwinged grasshopper possesses remarkably strong
powers of flight allowing the species to disperse widely and to escape
deteriorating desert habitats as vegetation senesces and dries. Attracted by
city lights, flying swarms land at night piling up on streets and sidewalks in
enormous numbers. In Arizona during outbreaks, numerous adults have often been
recorded as invading crops. Unfortunately, no detailed study has been made of
the flights. We do not know the meteorological conditions, the time of day,
direction, duration, and distance of flights. Small-scale displacement of the
pallidwinged grasshopper was studied in a 2.5 acre plot in 1975 in western
Texas, 15 miles east of Alpine. Of the four grasshopper species marked and
recaptured, the pallidwinged grasshopper moved the farthest, an average
distance of 27 feet per day. Recovery of this grasshopper was low, 25 percent,
compared with the other two long-winged species, 36 and 53 percent, indicating
that after two weeks a large number of pallidwinged grasshoppers had flown out
of the plot area.
One of the few observations of actual flight of this
species was made in Nevada; where flights were often of long duration,
individuals commonly ascending well out of sight. In one case, a male circled
about a sagebrush slope for 17 minutes in a single flight before finally coming
to rest. In the Phoenix, Arizona area (altitude 1083 feet), pilots have
reported swarms at altitudes of 3,000 to 5,000 feet. Flushed grasshoppers fly
swiftly at heights of 2 to 3 feet often going more than 100 feet and beyond
A remarkable dispersal record of the species was made 7 September
1966 when adults were discovered along roadsides bordering a sugar plantation
at Ewa, Oahu, Hawaii. Specimens sent to the U.S. National Museum were
identified by A.B. Gurney. The Hawaiian infestation persisted in 1967 and 1968.
Probable source of the infestation was western North America indicating wind
transportation of a swarm.
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Appearance of the nymphal instars of Trimerotropis pallidipennis-their
sizes, structures, and color patterns. Notice progressive development of wing
pads. BL = body length, FL = femur length, AS = number antennal
Fig. 1, First Instar:BL 4.6-6.8 mm FL 2.7-3 mm AS
Fig. 2, Second Instar:BL 6.7-8.1 mm FL 3.6-3:9 mm AS
Fig. 3, Third Instar: BL 9.2-10.8mm FL5.4-5.8mm AS
Fig. 4, Fourth Instar:BL 13.8-15.5 mm FL 7.5-7.9 mm AS
Fig. 5, Fifth Instar:BL 13.7-20 mm FL 8.5-11.2 mm AS
6-10,Appearance of adult male and female of Trimerotropis
pallidipennis, spread wings of female, inner face of hindleg of female and
pod and opened pod.
Fig. 6, Adult Male:BL
20.5-24 mm FL 12-13.5 mm AS 24-26.
Fig. 7, Adult Female:BL 27-33 mm FL 13.5-16 mm AS
Fig. 8,Spread wings of female.
Fig. 9, Inner face of female hindleg.
Fig. 10, Egg pod and
opened egg pod showing eggs.
The pallidwinged grasshopper belongs to the diverse
bandwinged genus Trimerotropis which encompasses more than 40 described
species and several yet undescribed. The large number of species with many
shared color patterns and structural characteristics present a challenge for
accurate identification. Nevertheless a combination of characters make possible
the identification of the species. The pallidwinged grasshopper is a
moderately-sized tan or gray insect (Fig. 6 and 7) found chiefly in desert and
semidesert habitats. The tegmen bears two transverse dark bands that cross its
entire width; the distal end bears numerous brown spots. The center of the hind
wing has a relatively narrow but conspicuous black band; the wing disk ranges
from white to pale yellow, and the apical area is transparent (Fig. 8). Incised
twice near the front, the median carina of the pronotum is high on the prozona
and low but distinct on the metazona. The ventral edge of the pronotallobe is
straight, bearing no tooth. The inner medial area of the hind femur is black,
broken by two yellow bars (Fig. 9). The hind tibia is yellow. The venter is
solid cream to pale yellow.
The nymphs are identifiable by their structures and color
patterns (Fig. 1-5).
- Head with distinct triangular foveolae; carinae of
frontal costa straight in instar I and II, carinae slightly incurving at level
of antennal sockets in instars III to V; carinae connected by a bridge-like
ridge approximately at level of antennal sockets in all instars.
- Pronotum with distinct median carina feebly incised twice
in instar I, becoming more strongly elevated and clearly incised in instars II
to V; disk rugose on prozona, smooth on metazona; median carina elevated on
prozona, low on metazona.
- Hindleg: in instar I mainly black except basal fourth of
femur (outer area) pale, inner medial area black with pale distal bar; hind
tibia black with pale basal annulus; tarsus white except segment two and distal
half of last segment black. In instar II medial area of hind femur pale tan,
two dark bars on upper marginal area, inner medial area of hind femur with
three black and three pale tan bars; hind tibia black or pale tan. In instars
III to V outer and inner surface of hind femur pale tan with two or three black
bars; hind tibia yellow.
- Ground color tan spotted brown; venter yellow or
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The pallidwinged grasshopper hatches early in spring from
eggs that have overwintered in the soil. In south-central Arizona the species
starts to hatch in late February and continues hatching through March. In
west-central Utah (Millard County), hatching begins in late April. Based on the
appearance of adults and a nymphal period of 45 days, hatching in late April
occurs in southeastern Colorado (Bent County) and in eastern Wyoming (Goshen
County). In south-central Arizona a second generation begins to hatch in early
June. Only one generation develops in northern Arizona and northern states such
as Colorado, Utah, and Wyoming. The evidence suggests that several days after
being laid, the eggs cease development and enter a diapause. Yet in an
insectary at Mesa, Arizona, eggs kept under moist conditions in a mixture of
silt and sand hatched without a diapause in 13 to 21 days (mean 15.5 days) of
incubation (air 82° to 104°F, mean 93°F).
In nature rainfall appears to be a critical factor for eggs
to survive and hatch. In the Tule Hill site of Millard County, Utah, a moderate
population of adults inhabited the site in the summer of 1998, but no eggs
hatched by 22 June 1999 apparently having died because of drought.
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Nymphs appear early in spring when weather is variable but
food plants are usually green, nutritious, and plentiful. At this time the
length of the nymphal period of individuals ranges from 42 to 48 days. In
southern Arizona the nymphs develop during March and April, while in Colorado,
Utah, and Wyoming they develop in May and June. A second generation develops in
southern Arizona during June; and, under favorable conditions of moisture,
additional generations may develop later in the season. In a study conducted in
an outdoor screened insectary at Mesa, Arizona, researchers found that female
nymphs have five or six instars, while the males usually have five but a few
have six. The study also found that the nymphal period of grasshoppers reared
at relatively low temperatures in the laboratory (range 70° to 84°F,
mean 77°F) averaged 50 days for males and females with five instars and 60
days for females with six instars. The nymphal period of grasshoppers reared
during mid summer in the outdoor insectary at relatively high temperatures
(range 81 ° to 101°F, mean 91 OF) averaged 31 days for the males and 33
days for the females.
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Reproduction Depending on the location of the habitat, the
adult stage of the pallidwinged grasshopper is reached in mid to late spring.
In southern Arizona adults appear in mid April, while in Colorado, Utah, and
Wyoming they appear in early June.
During the day adults fly about and
may disperse widely. In the Alpine, Texas study marked adults were recaptured
for only 14 days. On the other hand, in a small favorable habitat of about one
acre in the desert of Millard County, Utah, adults have been found in residence
from 19 June to 29 August 1998, indicating a habitat fidelity of at least 67
Males make frequent local flights in which they crepitate
(snapping sounds produced by the hind wings). Observations indicate that
crepitation initiates pair formation of the sexes. Upon landing, the male walks
in a straight line to a resting female. Courtship consists of ordinary
stridulation which resembles a trilling sound to the human ear. One to eight
trills in quick succession are produced by males advancing toward females. A
receptive female remains still as the male approaches, mounts, and attaches his
genitalia to consumate mating.
Reproductive maturation of females in
nature has not been closely followed. However, in south-central Arizona adults
that fledged by the end of April in a habitat of succulent vegetation bore
well-developed eggs a week later, but no eggs were found in females inhabiting
Caged in pairs and sheltered in a screened insectary during
mid summer (76° to 101°F, mean 88°F), and fed a mixed diet of four
species of host plants, pallidwinged grasshoppers exhibited a high fecundity,
comparing favorably with other pest species of grasshoppers. Sixteen females
averaged 386 eggs each. One female laid a record 27 pods containing 955 eggs.
The preoviposition period was long with a minimum of 26 days and an average of
43 days. Average longevity of these females was 80 days. In nature the eggs are
laid in bare soil to a depth of approximately 1 inch. The pod is slightly
curved, narrow (118 inch in diameter), and 1 inch long (Fig. 10). Each pod
contains an average of 34 pale yellow eggs, 4.5 to 5 mm long.
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Ecology Irruptions of the pallidwinged grasshopper occur
sporadically in the deserts of western North America. In Arizona outbreaks have
been associated with above normal, well-distributed rainfall during the
preceding fall, winter, and early spring. The ample moisture provides favorable
soil conditions for the eggs and a steady supply of nutritious food plants for
the nymphs and adults. Populations inhabiting specific sites, however, have not
been monitored to determine the time required for the pallidwinged grasshopper
to reach high densities. In Idaho dense populations have numbered five adults
per square yard. Outbreaks are of short duration, usually only one year, at
most two. Evidently individuals of swarms that alight in cities die for lack of
food, while those that migrate into crops are destroyed with insecticides or
cultural practices. Between outbreaks, periods of usually three to four years,
pallidwinged grasshoppers are rare in desert habitats. Apparently, favorable
weather and the great fecundity of the species foster a rapid growth of
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Barnes, O.L. 1960. Observations on the desert
grasshopper, Trimerotropis pallidipennis pallidipennis, in
Arizona. J. Beon. Entomol. 53: 721-724.
Barnes, O.L. 1963. Observations on the
life history of the desert grasshopper (Trimerotropis pallidipennis
pallidipennis) in laboratory and insectary cages. J. Econ. Entomol. 56:
1983. Thermal limitations to escape response in desert grasshoppers. Anim.
Behav. 31: 1088-1093.
Joorn, A 1983. Small-scale displacements of grasshoppers (Orthoptera:
Acrididae) within arid grasslands. 1. Kansas, Entomol. Soc. 56:
Massion, D.D. 1983. An altitudinal
comparison of water and metabolic relations in two acridid grasshoppers
(Orthoptera). Comp. Biochem. Physiol. 74A: 101-105.
Otte D. and A
Joorn. 1977. On feeding patterns in desert grasshoppers and the evolution of
specialized diets. Proceed. Acad. Nat. Sci. Philadelphia 128: 89-126.
Scoggan, AC. and M.A. Brusyen. 1972. Differentiation
and ecology of common immature Gomphocerinae and Oedipodinae (Orthoptera:
Acrididae) of Idaho and adjacent areas. Melanderia 8: 1-76.
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