Twostriped Grasshopper
Melanoplus bivittatus (Say)
Link directly to photos of adults, nymphs,
or eggs.
Distribution and Habitat
M. bivittatus continental distribution map
Wyoming distribution map
The twostriped grasshopper, Melanoplus bivittatus (Say), occurs
widely in North America inhabiting tall, lush, herbaceous vegetation. Dense
populations may reside in tallgrass prairie, wet meadows, roadsides, ditch
banks, and crop borders.
Economic Importance
The twostriped grasshopper is a major crop pest causing much damage to
small grains, alfalfa, and corn. During outbreaks, it may completely destroy
crops. A population of 10 adults per square yard in a corn field will defoliate
the crop. Sorghum plants over 6 inches tall, however, are nearly immune
to attack. Experiments indicate that in feeding on spring wheat the twostriped
grasshopper wastes six times as much foliage as it eats. In urban areas
the twostriped grasshopper is a common pest of flowers and vegetables.
It is a large grasshopper. Collected from a roadside in Platte County,
Wyoming, males averaged 549 mg live weight and females 1,086 mg (dry weight:
males 166 mg and females 341 mg).
Food Habits
The twostriped grasshopper is a polyphagous species. It feeds on many kinds
of plants. Although grasses and cereals are eaten and damaged, rearing
experiments show that certain forbs furnish the nymphs with diets that
promote high survival, fast growth, and heavy weights. These host plants
belong to several plant families. Included are mustards, flixweed and pepperweed;
a plantain (broadleaf plantain); legumes (alfalfa and red clover); and
composites (greenflower, dandelion, chicory, prickly lettuce, giant ragweed,
and arrowleaf butterbur). Microscopic examination of crop contents and
field observations indicate that the following species may also be primary
host plants: ball mustard, western ragweed, prairie sunflower, perennial
sowthistle, kochia, and leadplant. The twostriped grasshopper feeds also
on dry litter found on the ground.
A meal for the twostriped grasshopper may be a single species of plant
but usually it consists of two or more species. Laboratory rearings demonstrate
that a mixed diet is more nutritious than a single plant diet. The diets
of particular populations vary depending on the kinds of plants present
in their habitats.
Migratory Habits
The twostriped grasshopper exhibits migratory behavior during both nymphal
and adult stages. At high densities nymphs move in bands when they reach
the third and older instars. Populations invade crops from crop borders
and roadsides where eggs are concentrated and nymphs reach densities as
great as 500 per square yard. Nymphs start migration around 10 a.m. when
skies are clear and temperature has risen to 75°F. This activity may
occur through the day until 6 p.m. Wind has little effect on movement.
Adults begin flying when temperatures reach 86° to 90°F. Flying
with the wind at heights of 600 to 1,400 ft above ground level, they may
travel long distances. Swarms of adults also move upwind by low, short
flights in search of green food. At high densities, twostriped grasshoppers
develop longer wings and slimmer bodies and are more adapted to flight
than are low density, solitary individuals.
Identification
The twostriped grasshopper is one of the two largest species in the genus
Melanoplus. The other is the differential grasshopper, M. differentialis
(Thomas). Both species are often found together in the same habitat.
The nymphs of the twostriped grasshopper (Fig.
1-5) are identifiable by their spots, stripes, and color patterns:
(1) Compound eye brown with many light tan spots and no dark bands.
(2) Front of head tan or green with dark spots; line of dark spots on
carinae (ridges) of frontal costa.
(3) Pronotum with light, horizontal stripe at top of lateral lobe; above
the stripe a fuscous or brown band at the edge of pronotal disk.
(4) Gena colored tan or green and spotted, without light crescent below
compound eye.
(5) Hind femur with black stripe entire, not interrupted by pale band.
Stripe fills upper medial area of hind femur except at proximal end and
encroaches slightly on the lower medial area.
(6) Hind tibia green or buff with spines or tips of spines black. Front
(anterior edge) of tibia fuscous.
(7) General color green or tan.
The adult male (Fig. 6) is easily identified
by the shape of the cercus (Fig. 9).
Both the male and the female (Fig. 7)
have two distinctive light yellow stripes running down the dorsum of the
head, pronotum, and tegmina (Fig. 8).
The stripes come together posteriorly on the tegmina forming a triangle.
Hatching
The twostriped grasshopper is an early-hatching species. It is one of the
first species to appear in habitats of roadsides and field borders. Eggs
(Fig. 10) begin embryonic growth in
the summer of deposition and attain 60 to 80 percent development before
they go into diapause for the winter. When soil temperatures rise in spring,
the embryos complete development and hatching begins. Eggs start to hatch
eight to ten days ahead of those of the migratory grasshopper, Melanoplus
sanguinipes (F.) The hatching period may last from four to six weeks
depending mainly on soil temperatures in spring. Hatching may come in two
or more bursts following rain and warm temperatures.
Nymphal Development
Nymphs develop and grow in spring when vegetation is young and green. It
takes around 40 days for them to reach the adult stage. Dense populations
of nymphs do much shifting about and often migrate into crops, particularly
barley and wheat. Because of an extended period of hatching, nymphs may
be present in the habitat for as long as 75 days.
Adults and Reproduction
Although the exact date of adult emergence may vary annually by as much
as 50 days, this event usually occurs in the first part of summer. Grasshoppers
that have moved into crops return to crop borders and roadside habitats
for reproduction. Without signaling, a male will stealthily approach a
female and make a copulatory leap. After mounting and while attaching his
genitalia, the male performs a courtship ritual by shaking his hind femora
for three or four seconds. Females have a preoviposition period of one
to two weeks before depositing their first clutch of eggs. Favored sites
for oviposition are ditch banks that face south and crop borders with compact
drift soil. The females select crowns of grass or roots of weeds on which
to deposit their clutch. Pods may contain from 50 to 108 eggs. Pods are
curved, one and one-eighth to one and one-half inches inches long and one-quarter
inch in diameter (Fig. 10) They are
delicate and easily broken in sifting them from the soil. Eggs are olive
and 5.1 to 5.3 mm long. Fed a nutritious diet of radish leaves, caged grasshoppers
have averaged 450 eggs per female. The average number of pods and eggs
produced in nature is unknown.
Most populations of the twostriped grasshopper have a one-year life
cycle, but in mountain parks of British Columbia at altitudes above 3,000
feet, populations take two years to complete a life cycle. A two-year life
cycle may also occur among populations inhabiting meadows of the Rocky
Mountains.
Population Ecology
The twostriped grasshopper became a pest when agricultural development
in the West fostered large populations of the insect. Early settlers unwittingly
sowed seeds of various weeds along with their crops, thus introducing nutritious
new host plants for this grasshopper. The weeds also grew luxuriantly along
crop borders, road sides, and ditch banks. This environment provided essential
habitats, while south-facing ditch banks and compact drift soil at field
margins furnished ideal egg laying sites.
These factors and favorable weather over a few consecutive years allow
populations to irrupt. In eastern North and South Dakota such favorable
conditions combined to precipitate one of the worst outbreaks of the twostriped
grasshopper and differential grasshopper in agricultural history. Populations
increased slowly for three years, 1928 to 1930. Both species reached phenomenal
numbers in 1931 and 1932. They devastated fields of alfalfa, small grains,
corn, vegetables, and a variety of fruit and shelterbelt trees. In 1933
and 1934 a severe drought not only ruined crops and other vegetation but
also terminated the grasshopper outbreak.
Daily Activity
The twostriped grasshopper is a diurnal insect. Its activities occur during
the daylight hours when weather is warm and the skies are clear (Table
1). The tall vegetation of its habitat influences its behavior. In
the evening before sunset as temperatures cool, both nymphs and adults
climb the plants and rest, moving from halfway up to nearly the top of
the vegetation. In these positions they rest through the night. Shortly
after sunrise, the grasshoppers are warmed by the rays of the sun and begin
to descend from their overnight perches. On the ground they may continue
sunning themselves or begin to feed and then to migrate. Nymphs are usually
on the ground from 6 to 11 a.m.
Selected References
Bailey, C. G. and M. K. Mukerji. 1976. Feeding habits and food preferences
of Melanoplus bivittatus and M. femurrubrum (Orthoptera:
Acrididae). Can. Entomol. 108: 1207-1212.
Bird, R. D., W. Allen and D. S. Smith. 1966. The responses of grasshoppers
to ecological changes produced by agricultural development in southwestern
Manitoba. Can. Entomol. 98: 1191-1205.
Drake, C. J., G. C. Decker and O. E. Tauber. 1945. Observations on oviposition
and adult survival of some grasshoppers of economic importance. Iowa State
College J. Sci. 19: 207-223.
Fisher, J.R. 1994. Temperature effect on postdiapause development of
embryos of three species of Melanoplus (Orthoptera: Acrididae).
Ann. Entomol. Soc. Am. 87: 604-608.
MacFarlane, J. H. and A. J. Thorsteinson. 1980. Development and survival
of the twostriped grasshopper, Melanoplus bivittatus (Say) (Orthoptera:
Acrididae), on various single and multiple plant diets. Acrida 9: 63-76.
Mukerji, M. K., R. Pickford and R. L. Randell. 1976. A quantitative
evaluation of grasshopper (Orthoptera: Acrididae) damage and its effect
on spring wheat. Can. Entomol. 108: 255-270.
Moore, H. W. 1948. Variations in fall embryological development in three
grasshopper species. Can. Entomol. 80: 83-88.
Parker, J. R. and R. L. Shotwell. 1932. Devastation of a large area
by the differential and the two-striped grasshoppers. J. Econ. Entomol.
25: 174-196.
Putnam, L. G. and R. H. Handford. 1958. Two-year and one-year life cycles
in Melanoplus bivittatus (Say) (Orthoptera: Acrididae) in western
Canada. Proc. Tenth Internatl. Congr. Entomol., Montreal 1956, 2: 651-656.
Smith, D. S. 1966. Fecundity and oviposition in the grasshoppers Melanoplus
sanguinipes (F.) and Melanoplus bivittatus (Say). Can. Entomol.
98: 617-621.
Smith, D. S. and N. D. Holmes. 1977. The distribution and abundance
of adult grasshoppers (Acrididae) in crops in Alberta, 1918-1975. Can.
Entomol. 109: 575-592.
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