Sagebrush Grasshopper
Melanoplus bowditchi Scudder
Link directly to photos of adults, nymphs,
or eggs.
Distribution and Habitat
M. bowditchi continental distribution map
Wyoming distribution map
The sagebrush grasshopper is distributed widely in western grasslands.
It inhabits the mixedgrass, shortgrass, desert, and bunchgrass prairies,
and certain desert shrub communities. In all of these vegetational units
its distribution depends upon the presence of sagebrush.
Economic Importance
The preference of the sagebrush grasshopper for silver sagebrush, a plant
that furnishes good to excellent browse in fall and winter for all classes
of livestock and game animals, makes this insect a potentially damaging
species. The low densities of this grasshopper, however, suggest economic
damage does not occur.
The sagebrush grasshopper is a medium-sized species of the diverse genus,
Melanoplus. Live weights of males average 394 mg and of females
434 mg (dry weights males 80 mg, females 144 mg).
Food Habits
The sagebrush grasshopper feeds almost exclusively on several species of
sagebrush. Two of the six species known to be ingested are evidently primary
host plants, silver sagebrush, Artemisia cana, and sand sagebrush,
A. filifolia. Crop contents of grasshoppers collected in western
North Dakota contained 97 percent silver sagebrush and 5 percent fringed
sagebrush, while crop contents of grasshoppers collected in western Nebraska
consisted of 88 percent sand sagebrush and the remainder undetermined forbs
and pollen. The geographic range of the two host plants taken together
matches closely the range of the grasshopper. Four other species - big
sagebrush, fringed sagebrush, tarragon, and cudweed sagewort - are ingested
in small amounts. These occur in the mixedgrass prairie along with silver
sagebrush, so the nearly exclusive consumption of the latter indicates
that it is the preferred species. Sand sagebrush grows on sand dunes and
sand hills where silver sagebrush frequently does not occur and serves
as the host plant in these more limited habitats.
The sagebrush grasshopper often attacks silver sagebrush at the edge
of leaves. It may also cut a leaf at its base and hold onto it with the
front tarsi to consume the entire leaf. In addition, this grasshopper feeds
on the flowers of silver sagebrush when they become available. Adults have
been observed feeding horizontally on a small mat-forming lichen on the
ground.
Dispersal and Migration
Little is known about the dispersal and migration of the sagebrush grasshopper.
Possessing long wings that extend beyond the end of the abdomen, the species
evidently has the capacity to disperse and migrate. Observations have been
made of its evasive flights. These are silent and usually straight at heights
of 12 to 15 inches for distances of 1.5 to 12 feet. The flushed grasshopper
takes off from its perch on silver sagebrush or from the ground and usually
lands on vegetation, either its host plant or a grass culm.
Identification
The sagebrush grasshopper is a pale to dark gray, medium-sized, spurthroated
grasshopper (Fig. 6 and 7). The wings are long,
extending 3 to 5 mm beyond the end of the abdomen. The shape of the male
cercus, an essential character for identifying and separating the numerous
species of Melanoplus, is elongated and slender (Fig.
8). The medial area of the hind femur is marked by chevrons that are
separated by white lines; chevrons are darker dorsally and lighter ventrally.
The hind tibiae are light to medium blue.
Nymphs of the sagebrush grasshopper are identifiable by their shape,
structures, and color patterns (Fig. 1-5).
1. Head. Face nearly vertical (slightly receding); compound eye with
pale yellow spots; pale yellow crescent beginning on gena below compound
eye and running onto lateral lobe.
2. Pronotum. Lateral lobes below crescent are light gray and weakly
spotted; disk medium gray or brown, darker than lateral lobes and with
many fuscous spots.
3. Hindleg. Femur with medial area having dark stripe centrally located
in instars I and II and dorsally in instars III to V; tibia pale gray in
instars I to IV, pale blue in instar V; front of tibia fuscous in all five
instars.
4. General body color pale gray with darker markings.
Specimens of this species may be picked up in a sweep net when a surveyor
passes close to host plants.
Hatching
In the mixedgrass prairie of eastern Wyoming, eggs of the sagebrush grasshopper
begin to hatch during the first week of June. Hatching occurs about three
weeks after the bigheaded grasshopper begins to hatch, and places the sagebrush
grasshopper in the intermediate- hatching group of species.
Nymphal Development
Nymphs develop rapidly, taking about 30 to 40 days to become adults. They
are located close to their host plants: silver sagebrush or sand sagebrush.
Adults and Reproduction
Adults begin to appear in the habitat during the first week of July. Part
of the nymphal population continues to molt to this final stage for as
long as a month. Adults are present in the habitat for three months, July
through September. No observations of courtship, mating, or oviposition
in nature have been made. In the laboratory, females readily oviposit in
bare soil. One caged female was observed ovipositing for at least 30 minutes.
During this time she was attended by a male. Upon completion of oviposition
and extraction of her abdomen, she covered the hole with soil by working
her ovipositor back-and-forth and sideways. The pod is three-quarters inch
long; froth surrounds a cluster of 12 to 13 eggs held together by scanty
secretion of the accessory gland. The eggs are tan and 4.5 to 4.9 mm long
(Fig. 9).
Population Ecology
The population ecology of the sagebrush grasshopper remains unstudied.
We do know that it has an extensive range within which its dispersion is
patchy and limited by the distribution of its host plants. Other important
population characteristics such as density, fecundity, mortality, and capacity
for increase are unknown. However, we know that it is an insignificant
component of grasshopper outbreaks.
Daily Activity
The sagebrush grasshopper is a phytophilous species because it spends much
of its daily life on the host plant. The precise proportion of time spent
between the host plant and the ground, however, remains undetermined. During
the night both nymphs and adults roost 6 to 16 inches high, head up, on
stems of silver sagebrush. For about two hours after sunrise they remain
on the host in these resting positions. Subsequently, they adjust their
positions so that their sides or backs are exposed to the warming rays
of the sun. By 9 a.m. many individuals have jumped to the ground and bask
horizontally. On the ground, they turn a side perpendicular to rays of
the sun and lower the exposed hindleg. About 10 a.m., when the soil surface
temperature has risen to 70°F, they begin to stir and potter. Shortly
afterwards they jump back into their host plant to feed. Method of mate
location, courtship, and where the adults mate, either on the host plant
or on the ground, are unknown. The grasshoppers again bask in late afternoon
and by 6 or 7 p.m. most are roosting on the host plant where they remain
overnight.
Selected References
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. K. 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.
Newton, R. C., C. O. Esselbaugh, G. T. York, and H. W. Prescott. 1954.
Seasonal development of range grasshoppers as related to control. USDA
ARS Bur. Entomol. and Plant Quarantine, E-873.
Vickery, V. R. and D. K. McE. Kevan. 1983. A monograph of the orthopteroid
insects of Canada and adjacent regions. Lyman Entomol. Museum and Research
Laboratory. Memoir 13. (Ste. Anne de Bellevue, Quebec, Canada).
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