Arphia conspersa Scudder
Wyoming Agricultural Experiment Station Bulletin 912
Species Fact Sheet
by Robert E. Pfadt
Geographic range of Arphia
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The specklewinged grasshopper enjoys a wide distribution in western
North America that stretches from Alaska to Mexico. It inhabits all
of the grassland prairies and penetrates desert shrub communities
wherever grasses make up part of the vegetation. In Colorado and Idaho,
resident populations have been found in mountain meadows and other
open grasslands up to 11,000 feet.
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Although the specklewinged grasshopper feeds on quality forage,
its impact on grazing land is minimal due to low densities throughout
its distribution. Populations in desert grassland and in shortgrass
and mixedgrass prairie have been determined to range from 0.05 to
0.1 adults per square yard. In mountain habitats, numbers are less,
ranging from approximately 40 to 120 adults per acre. In some apparently
suitable habitats they appear to be absent. This species is in the
largest category of the three size divisions of rangeland grasshoppers.
Live weight of males from mixedgrass prairie in Platte County, Wyoming
averaged 251 mg, and of females 776 mg (dry weight: males 86 mg,
females 178 mg). Individuals from mountain habitats are smaller;
live weights of individuals from 10,170 feet in central Colorado
averaged 194 mg for males and 494 mg for females.
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The specklewinged grasshopper feeds primarily on grasses and sedges.
Sixteen species of grasses and three species of sedges have been
recorded in crop contents. Specific host plants ingested depend
on both the grasshopper's preferences and the availability of plants
in diverse grassland habitats. In the sand prairie of southeastern
North Dakota, Kentucky bluegrass made up 50 percent of the diet;
in the mixedgrass prairie of central Nebraska, prairie junegrass
made up 67 percent; in the mixedgrass prairie of eastern Colorado,
western wheatgrass and needleandthread in equal quantities made
up 58 percent of the diet; and in the shortgrass prairie of northern
Colorado, blue grama (27.6 percent), western wheatgrass (18.8 percent),
and downy brome (17.6 percent) made up 64 percent of the diet. Other
plants found in substantial amounts include threadleaf sedge, needleleaf
sedge, sand dropseed, and sixweeks fescue. Small amounts of forbs
(12 species), fungi, and arthropods are ingested by this grasshopper.
No doubt, the number of grasses and sedges known to be ingested
is still far short of the actual number fed upon by this grasshopper.
The specklewinged grasshopper feeds mainly from a horizontal position
on the ground, and eats dry grass litter, recumbent attached leaves,
or green leaves cut by itself. It attacks a standing leaf by raising
up diagonally on its hind legs and cutting the leaf about one-half
to one inch above the base. It may hold onto the cut portion with
the front tarsi and feed to the tip, or it may drop the cut portion
and return to the ground to eat the fallen leaf. Sometimes it will
eat the remaining green stub from a horizontal position.
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The specklewinged grasshopper has strong powers of flight, possessing
long wings that extend beyond the end of the abdomen in both males
and females. Appetitive flights of the males occur regularly and
are accompanied by a crackling sound called crepitation. These flights
are comparatively rare in females. The sound is produced by the
wings, but an explanation of the exact mechanism remains in dispute.
Appetitive flights last one to three seconds and describe an arc
6 to 10 feet long and 3 feet high. The flights are a part of courtship
and function to bring the sexes together. Because of its behavior
to aggregate, the specklewinged grasshopper has low vagility. Evidence
for its dispersal is present in montane settings. It often colonizes
regrown road cuts and cleared chaparral within five years, wherever
nearby populations are present. No records of migration exist for
Evasive flights are made by both males and females beginning about
three hours after sunrise when soil temperatures have risen above
60°F. The flights range from 4 to 45 feet in length and from 6 inches
to 2 feet high. They are usually sinuous and accompanied by crepitation.
Silent escape flights may occur and extend from 30 feet to over
several hundred feet with the wind. The fleeing grasshopper lands
horizontally on the ground and often turns to face the intruder.
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Figures 1-5. Appearance
of the five 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
First Instar: BL 4.8-6.1 mm FL 2.8-3.1 mm AS 13.
Second Instar: BL 6.4-8 mm FL 3.8-4.2 mm AS 15-16.
Third Instar: BL 9-11.5 mm FL 5.3-6.5 mm AS 17-18.
Fourth Instar: BL 12-15.5 mm FL 6.9-8.3 mm AS 20-21.
Fifth Instar: BL 15-18 mm FL 8.7-10.6 mm AS 23-24.
Figures 6-10. Appearance
of the adult male and female, head, wings, and eggs.
Adult Male: BL 20-21 mm FL 11-12.2 mm AS 23-25.
Adult Female: BL 30-37 mm FL 14-17 mm AS 24-25.
Fig. 8, View of head
and pronotum of adult female.
Fig. 9, Forewing (tegmen)
and hindwing of female.
Fig. 10, Egg pod and
several loose eggs.
The specklewinged grasshopper, prevalent as adults in spring, is
a wide-ranging western species. Its genus, Arphia, consists
of 16 species. Of these, only the redwinged grasshopper, Arphia
pseudonietana (Thomas), has an equally wide distribution in
the West. Adults of this species, present in late summer and fall,
are separated seasonally from adults of the specklewinged.
The adult specklewinged grasshopper (Fig. 6 and 7) is a large rangeland
species, the female being much larger than the male. The lateral
foveolae of the head are triangular or quadrilateral. The median
carina of the pronotum is low but distinct, uniformly elevated,
and incised once in front of the middle (Fig. 8). The body is brown
except for a yellow abdomen. The tegmina are brown with dark brown
speckles and, when folded, often form a pale tan or yellow median
stripe. The disk of the hind wing is usually red but may be yellow
(Fig. 9). The hind tibia is pale yellowish green with a fuscous
annulus at each end.
The nymphs (Fig. 1-5) are identifiable by their shape, external
structure, and color patterns.
- Instar I. Head conspicuously large and rounded; segments of
maxillary and labial palps brown with distal ends pale yellow.
General body color dark brown. Pronotum with low, entire median
carina; lateral lobe black with a triangular light tan patch postero-ventrally
(Fig. 1). Hind tibia dark red; hind tarsus black on first segment
and distal two-thirds of last segment with middle white.
- Instars II and III. Head rounded, face nearly vertical, lateral
foveolae triangular or quadrilateral. Pronotum with low, median
carina (entire or weakly incised) and with disk tectate (rooflike);
lateral lobes of pronotum brown with dark brown speckles and marks
(without triangular light patch). Hind tibia shiny black; hind
tarsus black at both ends and pale in middle.
- Instars IV and V. Head vertically elongated, not as rounded
as in earlier instars; lateral foveolae triangular or quadrilateral;
segments of maxillary and labial palps mainly pale. Pronotum with
low, uniformly elevated median carina incised once in front of
middle; disk of pronotum tectate. General body color brown with
dark brown speckles and marks; venter of abdomen green with brown
spots; hind tibia green and black.
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The specklewinged grasshopper is a late-hatching species. First
instars begin to appear in mid-July in the mixedgrass prairie of
eastern Wyoming and in the shortgrass prairie of eastern Colorado.
Hatching continues for about a month. A laboratory study has revealed
that females lay nondiapause eggs that hatch in 40 days at 77°F.
This study suggests that the species has a one-year life cycle under
favorable temperature regimes. On the other hand, field studies
on the plains of central Saskatchewan and in the mountains of Colorado
indicate a two-year life cycle. As with several other grasshopper
species, this grasshopper appears to have a one-year or a two-year
life cycle depending on the climate of its habitat.
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The nymphs of this species develop relatively fast. In mixedgrass
prairie at altitudes of 5,000 feet, they become third instars by
late August, and fourth and fifth instars by late September. The
majority are in the fifth instar, the stage that overwinters, by
October. At the onset of cold winter weather they become dormant.
Precisely where they seek shelter is unknown. Nymphs have been shown
to survive freezing at temperatures as low as -16°C. Surface ground
temperatures seldom get colder than this extreme. In winter, during
periods of mild weather, some nymphs become active and may even
molt to the adult stage.
The time of general metamorphosis to adulthood comes in early spring
and varies as a function of weather, latitude, and altitude. In
the mixedgrass prairie of eastern Wyoming, adults are present in
April, but in high mountain habitats of Colorado adults may not
emerge until July.
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Adults remain in the same general area in which they developed
as nymphs. Densities of the males and females are apparently high
enough on the plains to present no difficulty in mate location.
In the mountains, however, very low densities present a problem
of mate location that is solved by the aggregation flights of males.
These flights are also made in all habitats of the plains. At the
peak of daily activity, males make aggregation flights every three
to four minutes.
Courtship is conducted on the ground. A male can detect a female
from a distance of at least 2 feet away. He moves toward her in
a series of spurt-runs; that is, he runs making several complete
leg movements, then pauses and stridulates emitting one to three
chirps. When he approaches within 1 inch of the female, he orients
to her face-to-face. They wave their antennae at one another and
the male continues to chirp. Next, the male moves to the female's
side, then faces and sometimes butts her thorax. The male continues
chirping and places his front tarsus on her middle femur and stomps
the ground rapidly with his hind tarsi. He then produces a series
of four or five chirps and mounts the female from the rear. If he
is accepted, the pair copulates. A receptive female may actively
solicit attention from a male by presenting her side, lowering the
near hindleg, and raising both the opposite hindleg and the tegmina,
which exposes the whole abdomen. One successful copulation of a
pair was observed to last 23 minutes.
A gravid female selects bare ground when she is ready to oviposit.
She bores more than 2 inches into the soil and deposits a clutch
of 20 to 21 eggs. After extracting her abdomen, she covers the hole
by pulling debris over the pod and tamps it down with her ovipositor.
The eggs are light brown to brown, and range in length from 4.5
to 5.2 mm (Fig. 10). Pods are long and usually break in extracting
them from the soil. One entire pod measured one and five-eighths
inches long. Neither the potential nor realized fecundity of this
grasshopper is known.
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Recorded populations of the specklewinged grasshopper have been
small in all habitats. Densities have ranged from 0.05 to 0.1 adults
per square yard in desert, northern mixedgrass, and shortgrass prairies.
Populations on the high altitude mesa of the Gunnison River in Colorado
tend to gather in clusters, occupying 200-400 feet diameter areas
within an apparently suitable and much larger habitat. Twenty to
40 adults per acre is the usual density; seldom do densities reach
120 adults per acre even in the clusters. In 1970, populations residing
on the mesa above 9,200 feet crashed, but populations at lower altitudes
were nearly normal. It is likely that an unusually cold winter killed
the nymphs but not the diapausing eggs, which hatched and allowed
normal population densities of nymphs in August and September 1970.
A small number of nymphs in 1971 indicated there was no recovery
of the 1970 brood. Causes of population fluctuations at lower altitudes
east of the Rocky Mountains have not been studied.
Of biological interest is the geographic isolation of populations
with red or yellow wings. Specific color morphs are associated with
particular geographic regions, and between these regions narrow
zones of hybrids and mixed colors exist. Predominantly redwinged
populations occupy the high plains east of the Rocky Mountains.
In central Colorado, yellow morphs occupy isolated grassland habitats
of pinyon-juniper and high coniferous forest.
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Because of the generally low densities of the specklewinged grasshopper,
few observations have been made of its daily activities. Apparently
the adults rest horizontally on the ground at night, their body
temperatures declining to the low ambient temperatures of spring.
Immobile at dawn, they begin to stir as the sun rises and then bask,
orienting their sides to the warming rays. At a soil surface temperature
of 57°F they are able to jump but not fly to avoid an intruder.
Flight becomes possible at soil surface temperatures a few degrees
above 60°F. Feeding begins around 10 a.m. and oviposition around
11 a.m. (MDT). In montane habitats the conspicuous spontaneous flights
of males peak between 10 a.m. and noon.
High temperatures suppress activity. Whenever the soil surface
temperature reaches 105°F, individuals either assume a stilt posture
(legs extended to lift the body off the ground) or move on the ground
to the shade of plants. Even without extreme heat, activity in the
afternoon subsides. One female was discovered resting horizontally
on the ground in a nonbasking orientation at 2:40 p.m. More observations
on the behavior of this grasshopper are needed to provide a complete
picture of its daily activities.
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Alexander, G. and J. R. Hilliard, Jr. 1969. Altitudinal
and seasonal distribution of Orthoptera in the Rocky Mountains of
northern Colorado. Ecol. Monogr. 39: 385-431.
Gillis, J. E. and K. W. Possai. 1983. Thermal niche
partitioning in the grasshoppers Arphia conspersa and Trimerotropis
suffusa from a montane habitat in central Colorado. Ecol. Entomol.
Pfadt, R. E. and R. J. Lavigne. 1982. Food habits
of grasshoppers inhabiting the Pawnee site. Wyoming Agr. Exp. Stn.
Sci. Monogr. 42.
Pickford, R. 1953. A two-year life-cycle in grasshoppers
(Orthoptera: Acrididae) overwintering as eggs and nymphs. Can. Entomol.
Schennum, W. E. and R. B. Willey. 1979. A geographical
analysis of quantitative morphological variation in the grasshopper
Arphia conspersa. Evolution 33: 64-84.
Willey, R. B. and R. L. Willey. 1969. Visual and
acoustical social displays by the grasshopper Arphia conspersa
(Orthoptera: Acrididae). Psyche 76: 280-305.
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