Twostriped Slantfaced Grasshopper
Mermiria bivittata (Serville)
Link directly to photos of adults, nymphs,
Distribution and Habitat
M. bivittata continental distribution map
Wyoming distribution map
The twostriped slantfaced grasshopper is widely distributed in North
America. Its center of distribution is in the tallgrass prairie where it
may reach densities of one adult per square yard in unplowed native grassland.
Its habitat consists primarily of tall grasses: big bluestem, yellow indiangrass,
and switchgrass, and it frequently inhabits these grasses on slopes and
hills. Small, edaphic stands of tall grasses in the mixedgrass, shortgrass,
bunchgrass, and desert prairies also provide suitable habitats for the
species. In addition, this grasshopper may live in luxuriant stands of
midgrasses in the mixedgrass prairie.
The twostriped slantfaced grasshopper is a frequent and common species
in the tallgrass prairie and is a potentially damaging pest. It feeds on
valuable forage grasses and occasionally reaches outbreak densities, as
it did in native grass pastures of eastern Kansas in 1939. It is a large
grasshopper; live weights of males from eastern Wyoming average 222 mg
and females 784 mg (average dry weight of males 63 mg, females 204 mg).
An estimate of damage indicates that an individual consumes 3.4 gm dry
weight of grass during its lifetime, an amount greater than the bigheaded
grasshopper, Aulocara elliotti, which consumes 2.0 gm. Nevertheless, it
rarely becomes a significant pest because densities usually remain light
and grass production plentiful in the tallgrass prairie.
A quantitative study of the impact of grasshoppers on tallgrass prairie
disclosed no significant differences in above ground biomass of vegetation
between plots with five grasshoppers per square yard and plots with 11
grasshoppers per square yard (early instars). In these studies the twostriped
slantfaced grasshopper was a subdominant in an assemblage of 15 species
in which Phoetaliotes nebrascensis, a grass feeder, was the dominant
species. These data indicate that in the tallgrass prairie where grasshopper
densities are lower and vegetation production higher than in the drier
western grasslands, the impact of grasshoppers is slight and often unmeasurable.
The twostriped slantfaced grasshopper is a grass feeder. Enjoying a wide
distribution in North America, the species exploits a variety of grasses
that grow in its diverse habitats. In the tallgrass prairie of eastern
Kansas, examination of crop contents has shown that it feeds upon sideoats
grama, tall dropseed, and yellow indiangrass; in the northern mixedgrass
prairie of western Nebraska, it feeds upon prairie sandreed, western wheatgrass,
big bluestem, and on eight other grass species; in the blackland (tallgrass)
prairie of northeastern Texas, it feeds upon big bluestem, silver beardgrass,
prairie dropseed, and several species of grama. This grasshopper has been
found to feed on a total of 18 species of grass and on threadleaf sedge.
Its dietary, in addition to the grasses already mentioned, includes little
bluestem, sand bluestem, blue grama, downy brome, smooth brome, sand dropseed,
needleandthread, and hairy grama. Preference tests of caged individuals
in a Texas insectary showed that the grasshoppers chose Bermuda grass,
an introduced species, and prairie dropseed for food in preference to big
bluestem and silver beardgrass.
The twostriped slantfaced grasshopper feeds on green leaves of its host
plant. It may attack a plant in three ways. First, sitting vertically,
head- up, and near the middle of a wide leaf (sand bluestem), it holds
onto its food with the front tarsi and eats from the edge to the midrib,
progressing toward the tip. Nymphs and young adults consume lengths of
leaf 1 to 2 inches long, causing characteristic semi-elliptical damage.
In the second method of attack, the grasshopper, also in a vertical, head-up
position, cuts a narrow leaf (needleandthread) near the tip and holds onto
a 1 to 2 inch section with the front tarsi and consumes the whole section.
The third method of attack involves the grasshopper feeding on a bent over
or recumbent leaf from a horizontal orientation. It then progresses from
the middle of the leaf for a short distance toward the base. Feeding bouts
of the adults last as long as 7 to 10 minutes. By the end of the season
the culms of sand bluestem are stripped of nearly all their leaves and
the bunch-like leaves of young plants are partially consumed.
During feeding, the twostriped slantfaced grasshopper may cut and drop
sections of leaf, which can still be found on the ground around each plant
at the end of the season. In the tallgrass habitat, unlike the mixedgrass
prairie, the cut leaves remain uneaten by grasshoppers and become part
of the ground litter.
Dispersal and Migration
The twostriped slantfaced grasshopper has long wings that extend to the
end of the abdomen. It is a strong and adept flyer. In flushed flights
it flies distances of 2 to 12 feet at heights of 9 to 36 inches. The flight
is silent and may be straight or sinuous. The grasshopper usually takes
off from vegetation and lands on vegetation, but it may also land on plant
litter or bare ground. It is able to turn at the end of a flight to land
vertically on an upright culm or stem. It can also veer in flight to land
within vegetated areas, although many individuals occasionally land in
inimical bare areas.
No special study of its dispersal or migration has been made. It has
not been found as an "accidental" in the mountains west of Boulder, Colorado,
even though it inhabits the adjacent plains and foothills. Although direct
evidence of its dispersal is lacking, we may speculate that the species
does disperse for the following reasons: 1) good capacity for flight; 2)
extensive range in North America; and 3) occupation of small edaphic habitats
in the drier grasslands.
The twostriped slantfaced grasshopper is a large, long-winged, colorful
insect (Fig. 6 and 7). It has a strongly slanted
face; the antennae are ensiform. A brown stripe beginning behind the compound
eye runs along the side of the head and onto the lateral lobe of the pronotum.
Four diagnostic characters of this species are: 1) the disk of the pronotum
rounds off onto the lateral lobe, i.e., it lacks lateral carinae (Fig.
8); 2) the pronotal disk margin is cut by three sulci; 3) sides of
occiput and pronotal disk without ivory stripe; and 4) one longitudinal
white or ivory streak on tegmen. The hind tibiae are orange and the body
is tan, often densely spotted brown (visible under low magnification).
In the West, this grasshopper broadly overlaps geographically and seasonally
with two other species of the genus - M. picta and M. texana.
All three look superficially alike, but adults can be easily separated
by a few distinguishing characters.
Mermiria texana has an ivory stripe on sides of occiput and pronotal
disk and it has two longitudinal white streaks on the tegmen, one above
base of hindleg and one above abdomen. Mermiria picta lacks the
ivory stripes on the occiput and pronotal disk and the streaks on tegmen
(M. bivittata has one streak), and it has well-developed lateral
carinae on pronotal disk and the lateral carinae are cut by two posterior
sulci (the anterior sulcus is visible on pronotal disk but does not cut
the carinae). One other species is known, M. intertexta. It is distributed
in the eastern United States along the Atlantic and Gulf coasts.
The nymphs (Fig. 1-5) are identifiable by
their color patterns, structures, and shape:
1. Head with face strongly slanted; antennae ensiform with proximal
segments triangular in cross section, distal segments tubular; lateral
foveolae triangular, invisible from above; narrow brown band beginning
behind compound eye runs along side of head and continues on dorsal edge
of lateral lobe; band faint in early instars.
2. Pronotum with lateral margin of disk rounding off onto lateral lobe;
margin of disk cut by three sulci; sulci weak in instar I.
3. Hind femur with upper medial area darker than the lower; hind tibia
yellow or pale gray.
4. Body yellow, tan, or green and densely spotted brown (visible with
The twostriped slantfaced grasshopper is a late-hatching species. In the
tallgrass prairie of eastern Kansas, first instars appear in early May,
while in the mixedgrass prairie of eastern Wyoming they do not appear until
early to mid June. The period of hatching in a habitat may last two weeks
Although nymphs hatch late and normally experience warm conditions and
favorable food supply, they develop at a relatively slow rate. Their minimum
nymphal period, completed by the males, is 40 days. The slow development
is probably due to exposure to the cooler temperatures of their luxuriant
grass habitat and their above-ground location on tall grass. Studies carried
out in eastern Wyoming indicate that the males have four instars and the
females five. Because of their smaller size, the males apparently require
fewer instars to achieve the weights necessary to metamorphose to the adult
stage than do the much larger females. This proposition suggests that the
males have a shorter nymphal period and thus emerge before the females.
Adults and Reproduction
Most adults remain in the habitat in which they hatched and developed as
nymphs. There they have the tall grasses for feeding, roosting, and shelter
and bare ground for oviposition. Several observations of male courtship
have been made. On approaching a female, a male stridulates with a burst
of two to five strokes of the femora. No information is available on mounting
and copulation nor on how soon adult females mate and lay eggs. The females
oviposit in bare ground near their host plant. Eggs are placed deep in
the soil, lying at depths between one and one-quarter and one and three-quarters
inches. The egg mass, which consists of 14 to 18 eggs, has no pod wall;
the eggs are held together by spots of froth (Fig.
9). The egg mass itself is one-half inch long. Eggs are tan or two-toned
tan and yellow and are 7.2 mm long. A long froth plug of one and one-quarter
inches lies above the eggs. The diameter of the plug measures one-eighth
inch or slightly more.
Studies on the population ecology of the twostriped slantfaced grasshopper
have been conducted in the tallgrass prairie where the species finds extensive
areas of its preferred habitat of tall grasses. These studies show that
populations fluctuate around low densities, rarely exceeding one adult
per square yard. Food supply is not the limiting factor, as the luxuriant
grass foliage of the tallgrass prairie remains plentiful except in cases
of heavy use by livestock. Elegant studies of the impacts of burning, which
occurs regularly via humans and lightning, show that the grass habitat
is maintained by reducing competition or invasion by forbs and shrubs thereby
favoring the graminivorous grasshoppers over the forb- or mixed-feeders.
A problem that still remains unsolved is the discovery of the factor or
factors that limit the size of populations of the twostriped slantfaced
The twostriped slantfaced grasshopper is a phytophilous species spending
most of its days and nights perched on grass. At night, nymphs and adults
rest vertically head-up on leaves or culms at heights of 8 to 12 inches.
As the sun rises and rays strike their perches, the grasshoppers begin
to bask by adjusting their positions so that one side receives the full
benefit of the radiant heat. They may bask for two to four hours before
they begin to feed or move about on host plants. Movement consists of descent
by backing down from their perches, crawling onto another leaf, or jumping
from one plant to another. If in jumping they land on the ground, they
immediately crawl up on a nearby grass plant. As do grasshoppers of other
species, they frequently preen their antennae and compound eyes, presumably
to remove dust particles that settle on these organs. High temperatures
cause them to change their positions on grass plants to the shady side.
When temperatures subside they again become active, feeding and moving
about. As evening approaches, they become quiescent and remain largely
immobile from 8:30 p.m. to 7 a.m. DST. Rain and cool temperatures extend
quiescence. Individuals continue to rest on their nocturnal perches until
the sun again shines on them.
In the sandhills grassland of central Nebraska, a study of time and
activity budgets of this grasshopper showed that in the daylight hours
(13.5 hours), the twostriped slantfaced grasshopper remained quiescent
88 percent of the time, fed 10 percent, and moved 1 percent.
Brusven, M. A. 1967. Differentiation, ecology and distribution of immature
slant-faced grasshoppers (Acridinae) in Kansas. Kansas Agr. Exp. Stn. Tech.
Campbell, J. B., W. H. Arnett, J. D. Lambley, O. K. Jantz, and H. Knutson.
1974. Grasshoppers (Acrididae) of the Flint Hills native tallgrass prairie
in Kansas. Kansas Agr. Exp. Stn. Research Paper 19.
Evans, E. W. 1988. Grasshopper (Insecta: Orthoptera: Acrididae) assemblages
of tallgrass prairie: influences of fire frequency, topography, and vegetation.
Can. J. Zool. 66: 1495-1501.
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.
Isely, F. B. 1938. The relations of Texas Acrididae to plants and soils.
Ecol. Monogr. 8: 551-604.
Joern, A., R. Mitschler, H. O'Leary. 1986. Activity and time budgets
of three grasshopper species (Orthoptera: Acrididae) from a sandhills grassland.
J. Kansas Entomol. Soc. 59: 1-6.
Otte, D. 1970. A comparative study of communicative behavior in grasshoppers.
Misc. Publ. Mus. Zool., Univ. Michigan, No. 141.
Wilbur, D. A. and R. F. Fritz. 1940. Grasshopper populations (Orthoptera,
Acrididae) of typical pastures in the bluestem region of Kansas. J. Kansas
Entomol. Soc. 13: 86-100.
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