Orangelegged Grasshopper
Spharagemon equale (Say)
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Distribution and Habitat
S. equale continental distribution map
Wyoming distribution map
The orangelegged grasshopper is widely distributed in the grasslands
of the western United States and Canada. It inhabits the tallgrass, mixedgrass,
shortgrass, bunchgrass, and desert prairies and also shrub-grass communities
of the Great Basin.
Economic Importance
The orangelegged grasshopper occurs as a subdominant species in rangeland
assemblages of grasshoppers. Because of the usually low densities (0.1
to 0.3 young adults per square yard), its feeding on both grasses and forbs
is usually of minor economic importance. On bunchgrass prairie of British
Columbia, however, it and Metator nevadensis caused considerable
damage to cattle ranges in 1921. The adults are conspicuous and relatively
large compared with the majority of rangeland grasshoppers. Live weight
of males and females captured in the mixedgrass prairie of eastern Wyoming
averaged 403 mg and 980 mg, respectively (dry weight: males 123 mg and
females 299 mg).
Food Habits
A polyphagous species, the orangelegged grasshopper feeds on diverse grasses
and forbs. Examination of 91 crops of grasshoppers collected in the sand
prairie of southeastern North Dakota revealed that the species had fed
upon 12 species of grasses, four sedges, and 11 forbs with no plant being
clearly preferred. Crops of 18 grasshoppers collected in western Nebraska
indicated a clear preference for blue grama. Two other grasses, needleandthread
and prairie sandreed, were contained in the crops as well as one forb,
lotus milkvetch, all in much smaller amounts than blue grama. Crops of
18 grasshoppers collected in the shortgrass prairie of north central Colorado
(Pawnee Study Site) contained a preponderance of milkvetch (Astragalus
sp.) and small amounts of four other forbs and three grasses.
Food preference tests of caged adults indicated that dandelion, blue
grama, needleandthread, and downy brome were preferred food plants. Western
wheatgrass, alfalfa, tumble mustard, kochia, and common lambsquarters were
fed upon but not preferred. Flixweed was only nibbled upon. Early reports
that this grasshopper prefers mustards have not been confirmed.
Five observations of the orangelegged grasshopper's method of attacking
grass and sedge have been made in the mixedgrass prairie. At least two
methods appear to be used. One is to raise up on the hindlegs and cut through
a leaf 1/2 to 1 inch above its base, hang onto the cut section of 1 to
3 inches with the front tarsi, and consume all of it. The other method
is to remain in a horizontal position on the ground, raise up on all legs
over a leaf stub, and consume it to the base.
Dispersal and Migration
The orangelegged grasshopper is a strong flier possessing long wings that
extend 5 to 10 mm beyond the end of the abdomen. Distances of flushed flight
range from 3 to 60 feet at heights of 4 inches to 6 feet. Patterns of flight
may be straight or sinuous with either a gradual linear descent before
landing or a right angle turn near the end of flight, followed by a gradual
or steep descent. Both males and females usually crepitate in flight. Appetitive
flight (unflushed flight) is common in the habitat; however, observations
have been too few to determine what needs of the grasshopper are being
met by these flights. Several investigators have noted aggregations of
adults on bare soil in an otherwise vegetated habitat; perhaps both flight
and walking are involved in movement to these spots, which may be important
in pair formation and courtship.
A few observations provide evidence for dispersal by this species. West
of Boulder, Colorado, where resident populations occur up to 7,200 feet,
two "accidentals" were found at 8,500 feet. On sidewalks and pavement in
downtown Billings, Montana on 1 August 1986, one male was collected along
with seven specimens of the migratory grasshopper, Melanoplus sanguinipes.
In the city of Boise, Idaho, on 22 July 1923, five males and five females
were collected at lights during the night along with specimens of Dissosteira
spurcata and Conozoa sulcifrons. Migrating swarms of the orangelegged
grasshopper have not been observed.
Identification
The orangelegged grasshopper is a relatively large bandwinged species.
The adult is tan with brown bands and maculations (Fig.
6 and 7). The median carina of the pronotum is low and cut once in
front of the middle; occasionally it is cut twice. The tegmina are crossed
by three bands, the distal band sometimes being faint. The hindwings have
a pale yellow disk and are crossed in the center by a broad, dark band
(Fig. 9). The hind tibia is orange.
The inner face of the hind femur is likewise orange and crossed with two
or three fuscous bands (Fig. 8).
The nymphs are identifiable by their color patterns and external structures
(Fig. 1-5).
1. Head with face nearly vertical, lateral foveolae triangular.
2. General color pale tan to brown.
3. Instar I
(a) Pronotum with median carina distinct and slightly elevated; carina
entire or faintly incised about one-fourth distance from posterior end.
(b) Hind femur with outer face fuscous for distal three-fourths, proximal
one-fourth tan and unspotted. Hind tibia fuscous. Hind tarsus with first
and second segments white, third segment white except distal third fuscous.
4. Instar II
(a) Pronotum with median carina distinct and slightly elevated; median
carina faintly incised, slightly more than one-third distance from posterior
end.
(b) Hind femur with outer face pale tan to tan crossed by two fuscous
bands. Hind tibia fuscous or fuscous and orange.
5. Instars III, IV, V
(a) Pronotum with median carina distinct and slightly elevated, weakly
incised near middle in instar III and anterior to middle in instars IV
and V.
(b) Hind femur with outer face pale tan or pale gray, sparsely spotted
brown and fuscous, two dark transverse bands usually present, knee usually
dark as well. Hind tibia orange.
Hatching
The orangelegged grasshopper is an intermediate-hatching species. In the
mixedgrass prairie of eastern Wyoming, first hatch of eggs depends on seasonal
weather and may occur as early as the last week of May or as late as mid
June. Hatching ensues two to three weeks after eggs of Aulocara elliotti
have begun to hatch. Field data indicate that the period over which hatching
takes place in a particular year is brief, ranging from 7 to 11 days.
Nymphal Period
When nymphs emerge in spring, grasses, sedges, and forbs are young and
nutritious. These supply an abundance and variety of host plants. The nymphal
period ranges from 49 to 64 days and averages 55 days. Both male and female
nymphs pass through five instars to reach the adult stage.
Adults and Reproduction
Depending on seasonal weather, adults may begin to appear in the mixedgrass
prairie of eastern Wyoming as early as mid July or as late as early August.
Remaining in the same habitat in which the nymphs developed, the adults
are present during August and September, and may survive into early October
when weather stays mild. Inspection of ovaries and field observation of
oviposition indicate that egg laying begins three to four weeks after the
adult stage is reached. No observation of courtship has been made, and
there has been only one observation of a pair in copulo (13 August 1969
at 9:15 a.m. DST). Gravid females deposit their eggs into bare soil. These
bare areas interspersed among the grasses range from 4 square inches to
much larger areas, such as cattle trails. Caged females readily oviposit
into containers of bare soil. They take 38 to 43 minutes from the start
of boring into the soil to extraction of the ovipositor. Females then spend
90 seconds brushing soil over the hole with the hind tarsi, using one leg
at a time. After this final act of protecting the eggs, the females walk
away. No males have been observed attending ovipositing females.
The pods range from 1 1/8 to 1 1/4 inches long (Fig.
10). The section of pod containing eggs is 3/4 inch long and 3/16 inch
in diameter. One-half inch above the eggs, the pod consists of light brown
froth. The pod contains 24 to 26 light brown eggs, 5 to 5.5 mm long. Recently
laid eggs are pale yellow. They eventually turn a light brown during their
early development.
Population Ecology
The orangelegged grasshopper is a subdominant member of rangeland grasshopper
assemblages. Where they occur in the mixedgrass prairie of Wyoming, densities
of young adults usually range from 0.1 to 0.3 per square yard. In spite
of low numbers, populations survive from year to year and appear to be
influenced by the same factors that affect other rangeland grasshoppers (Table
1). When economically damaging grasshoppers increase to outbreak numbers,
the orangelegged grasshopper may reach densities as high as two young adults
per square yard.
Daily Activities
A geophilous species, the orangelegged grasshopper lives most of its life
on the ground. At night, both nymphs and adults sit horizontally on the
ground under a canopy of grasses. Before the sun's rays strike the ground
early in the morning, a few individuals can be found sitting on small bare
areas of 2 to 6 square inches interspersed among mats of blue grama. They
face various directions with no particular orientation relative to the
sun.
One to two hours after sunrise, the majority of individuals have emerged
from their nighttime shelters and bask on bare ground. By turning a side
perpendicular to the sun's rays and lowering the associated flexed hindleg,
they expose the abdomen to the warming rays of the sun. The majority bask
from 7 to 9 a.m. DST at ground temperatures of 60° to 90°F and
air temperatures of 60° to 70°F (1 inch level). A few adults may
bask longer, and they appear to reach body temperatures above their preference.
These individuals then turn from the basking posture to face into or away
from the sun and assume a stilt posture.
Daily activities of feeding, mating, and ovipositing follow the basking
period and usually begin about 9:30 a.m. DST. When temperatures of bare
ground exceed 100°F and air temperatures exceed 90°F (1 inch level),
the adults leave bare ground and climb on top of blue grama or threadleaf
sedge, and face the sun directly to expose the least body surface. At these
times the grasshoppers are quiescent. When temperatures moderate later
in the day, they again become active. In the evening, activity ceases and
they again bask until nearly sunset at which time they seek shelter for
the night under canopies of grasses.
Selected References
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.
Anderson, N. L. and J. C. Wright. 1952. Grasshopper investigations on
Montana range lands. Montana Agr. Exp. Stn. Bull. 486.
Mulkern, G. B., K. P. Pruess, H. Knutson, A. F. Hagen, J. B. Campbell,
and J. D. Lambley. 1969. Food habits and preferences of grassland grasshoppers
of the North Central Great Plains. North Dakota Agr. Exp. Stn. Bull. 481.
Otte, D. 1970. A comparative study of communicative behavior in grasshoppers.
Misc. Publ. Mus. Zool., Univ. Michigan, No. 141.
Rockwood, L. P. 1925. On night flying and attraction to light in Acridiidae
and the relation of meteorological conditions thereto. Pan-Pacific Entomol.
2: 36-38.
Treherne, R. C. and E. R. Buckell. 1924. Grasshoppers of British Columbia.
Canada Dept. Agr. Bull. 39 - New Series.
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