Northern Grasshopper
Melanoplus borealis borealis (Fieber)
Link directly to photos of adults, nymphs,
or eggs.
Distribution and Habitat
M. borealis continental distribution map
Wyoming distribution map
The northern grasshopper, Melanoplus borealis borealis, ranges widely
in the north of North America. The species inhabits both lowland and mountain
sites, living in a variety of habitats that range from arctic tundra, wet
bogs, and swamps to moist mountain meadows. In the latter, large populations
consisting almost entirely of the northern grasshopper irrupt sporadically.
Economic Importance
Because the northern grasshopper feeds preferentially on certain forbs
and variably on certain grasses, a clear picture of its economic importance
on grazing lands eludes precise description. In mountain meadows of Montana
and Wyoming this grasshopper increases sporadically to densities as high
as 60 young adults per square yard. It thus has the potential of damaging
range forage; indeed, experienced entomologists have reported serious damage.
In 1955 in Utah's Beaver Mountain, Fishlake National Forest, grasshopper
survey entomologists reported a population of the subspecies M. borealis
palaceus, estimated at 50 young adults per square yard, that destroyed
reseeded meadow. High densities of this grasshopper have also been reported
in the mountains of Idaho and Oregon. A small outbreak of the northern
grasshopper in Wyoming occurred in 1995 in the Big Horn Mountains. One
infested meadow of approximately 100 acres supported a population estimated
at 20 young adults per square yard. A visual estimate of the vegetation
indicated that 90 percent had been grazed by August 9. A method of sorting
out the proportions consumed by each of the two chief herbivores, cattle
and grasshoppers, appeared impossible. Observations of damage in nature
are usually confounded by the presence of more than one herbivore. A study
with adequate controls is needed to determine the exact impact under various
circumstances. The problem is complex as the northern grasshopper is also
beneficial when it feeds on its preferred host plants of lupine and loco.
Grasshopper management specialists in Wyoming have postulated that in forb-rich
meadows, damage to range grasses may be much less than might be expected
from high densities of this species.
The northern grasshopper is a medium-sized species. Males collected
from a meadow in the Big Horn Mountains of northern Wyoming averaged 231
mg live weight and females 392 mg (dry weight: males 68 mg, females 111
mg). Live weight of Alaskan males one to two days after emergence averaged
254 mg and females 377 mg.
Food Habits
Northern grasshoppers feed principally on forbs but they may also feed
at times on certain grasses. In the crops of adults collected in the mountain
meadows of Wyoming, high percentages of lupine and loco have been found (Table
1). Other forbs selected include dandelion, Cerastium arvense,
species of thistle (Cirsium), and cinquefoil (Potentilla).
As do many species of grasshoppers, the northern grasshopper will feed
on arthropods, probably dead or dying grasshoppers, when they have the
opportunity. A bluegrass, Poa sp, has been found in large amounts
in crops of the northern grasshopper collected in one of three Big Horn
Mountain sites (Table 1).
Near Fairbanks, Alaska, in an open field, the northern grasshopper has
been observed feeding on four forbs: dandelion, red clover, Parnassia
palustris, and Petasites frigidus. In laboratory tests these
species were selected for food, confirming their status as preferred host
plants in the Alaskan habitat.
In 1962 in the sand prairie of southeastern North Dakota, flood waters
trapped a population of northern grasshoppers with a large number left
in the center of an ongoing study area. Analysis of crop contents revealed
that the grasshoppers were feeding on seven forbs, five grasses, and one
sedge. Favored foods in the order of percent ingested were Kentucky bluegrass,
53; western ragweed, 21; Missouri goldenrod, 15; and leadplant, 9.
In two-choice food preference tests of adults collected from a heavily
infested meadow in the Big Horn Mountains of Wyoming, the grasshoppers
preferred dandelion to white clover, alfalfa, silky loco, young wheat plants,
downy brome, Kentucky bluegrass, western wheatgrass, and Idaho fescue.
Of particular interest is the result of pairing dandelion and western wheatgrass.
After six hours, 75 percent of the dandelion was consumed but less than
1 percent of the wheatgrass. After 22 hours all of the dandelion had been
consumed and 20 percent of the western wheatgrass. Evidently the grasshoppers
will feed on wheatgrass when other food is lacking. After six hours 98
percent of dandelion and none of Idaho fescue were consumed. In contrast,
Kentucky bluegrass and downy brome were consumed at the same time as dandelion
but in unequal amounts. At the end of four hours, 90 percent of dandelion
and 25 percent of Kentucky bluegrass were consumed; at the end of six hours
20 percent of dandelion and 10 percent of downy brome.
In its mountain meadow habitat a few observations have been made of
the northern grasshopper’s method of attacking its food plant. A male was
seen to rise from a horizontal position on the ground onto the lower green
leaves of field chickweed, Cerastium arvense. Resting diagonally on the
plant with hindlegs on the ground supporting the body, the male consumed
a half-inch long leaf from tip to base. Another observation was of a female
attacking a forb sprout. Oriented horizontally on the soil surface and
over the plant, the female ate in two minutes the entire sprout from tip
to below ground level.
No observation of the grasshoppers feeding on lupine (Lupinus wyethi)
was made, but damage to leaves showed feeding from tip to base and gouging
from edges. Evidently the grasshoppers either climbed 3 to 10 inches on
the stems or they jumped onto the plant to reach the leaves.
Dispersal and Migration
The northern grasshopper possesses long wings, enabling it to fly and disperse.
Observations of the species in a 4 acre meadow near Fairbanks, Alaska,
provide insights into its dispersal behavior. Nymphs were concentrated
in loose groups around areas where the eggs had hatched, but upon the acquisition
of wings, the grasshoppers dispersed progressively into wider areas. When
temperatures rose from 74° F to 95° F, the adults flew frequently
and covered wide areas in relatively short periods. Another example of
this grasshopper's powers of dispersal happened fortuitously when one-half
of the meadow (2 acres) was mowed in mid July, 1967. Five days later the
density of adults in the unmowed half did not differ greatly from that
in the mowed. Ten days later, however, the density in the mowed half more
than doubled. Finally, 15 days after mowing the population was concentrated
in the mowed section. Because of the very short vegetation in this section
the ground temperature was 4 to 6° F higher than in the natural habitat.
Presumably, the grasshoppers moved because they preferred the higher temperatures.
A record of dispersal or of migratory flight was the discovery of a
male northern grasshopper on the ice of Grasshopper Glacier in the Crazy
Mountains of Montana, August 1988. The wings of the male were long, surpassing
the apex of the hind femur by 5 mm. Individuals of the species were present
in the adjacent meadow, so it is unknown whether the male came from close
by or from a distant meadow.
In meadows of the Big Horn Mountains, flushed flight by the northern
grasshopper is silent, short (1 1/2 to 3 feet), and at heights of 2 to
4 inches. The flight starts usually from the ground and ends on the ground,
with the grasshopper facing away from the intruder. In the meadow at Fairbanks,
Alaska flushed grasshoppers flew a distance of 1.6 to 5 feet at heights
of 1 to 2 feet. On very warm, dry, and windless days, some adults flew
3 feet high and covered a distance of 10 to 20 feet.
Identification
The northern grasshopper is a dark insect of medium size possessing wings
of variable length. The wings of males usually range from slightly short
of the apex of the hind femur to slightly beyond; the wings of females
are usually shorter covering three quarters of the abdomen (Fig.
6 and 7). The shape of the male cercus is diagnostic of the species
(Fig. 9). It is short, wide at the
base, gently curved upward, and narrows toward a blunt apex. The arms of
the furcula are long, reaching about halfway on the supraanal plate. The
subgenital plate curves dorsally, terminating in a blunt truncate end.
The medial area of the hind femur is usually entirely black, the upper
marginal area is usually fuscous, the lower marginal area is red but sometimes
yellow, and the hind tibia is red (Fig.
8). The abdominal venter is usually pale gray or pale green, but occasionally
yellow or two-toned, each sternum being fuscous in the anterior half and
olive in the posterior.
The nymphs are identifiable by their color patterns, shape, and structures
(Fig. 1-5). The first instars are distinctively
black except for a narrow mid dorsal brown band and a light crescent on
the side of the head and pronotum. Figure 1 pictures an unusually light
first instar.
1. Head with face nearly vertical and colored black, brown, tan, or
green; yellow or ivory crescent on side of head and lateral lobe of pronotum;
compound eye with many light spots, lower half darker than upper; narrow
light line and broad black bar behind compound eye.
2. Pronotum brown or green and usually with dark brown or fuscous spots.
Medial area of hind femur all black in instars I an II, broad dorsal stripe
in instars III to V; inner medial area in instars I and II all black and
occasionally marked by a light bar apically; in instar III like instar
II or the black area may be interrupted by two light bars, an apical and
a middle one; in instarts IV and V the inner black area becomes a dark
dorsal ensiform stripe (elongate triangular with base toward apex of hind
femur), light ventrally. Hind tibia is black in instar I with a light annulus
proximally, in instar II hind tibia is black or fuscous and tan. In instars
III to V hind tibia is usually dark tan with front fuscous.
3. General body color of instars II to V brown less often green, venter
generally olive or each sternum of the abdomen with front half fuscous
and rear half olive.
Hatching
In the grasshopper assemblages of mountain meadows, the northern grasshoper
hatches relatively early along with several other high-altitude species,
including Aeropedellus clavatus, Bruneria brunnea, Camnula
pellucida, Melanoplus alpinus, and M. bruneri. Before
hatching in spring, the eggs of the northern grasshopper require two winters
in the soil to break diapause. The species is one of several that have
a two-year life cycle. In the early 1950s field entomologists postulated
that this grasshopper required more than one year to complete its life
cycle when they observed reinfestations of areas a year after treatment
and were unable to explain the results by poor kills or migration of adults.
Subsequently, entomologists conducted field and laboratory experiments
that showed the eggs required two years in the soil before hatching.
A study of the life cycle of the northern grasshopper in the Big Horn
Mountains of Wyoming in 1994 and 1995 revealed that eggs begin to hatch
from June 1 to July 1. The exact date depended on time of snow melt, warming
of the soil, and elevation of site. On 4 May 1994, Powder River Pass (elevation
9,660) was 85 percent covered with snow. By May 24 the site became clear
of snow, and exactly one month later the eggs of the northern grasshopper
began to hatch. A late spring in 1995 delayed the start of hatch at this
site until July 1. In this year hatching continued for two weeks.
In a meadow site near Fairbanks, Alaska (elev. 450 feet) eggs of the
northern grasshopper began hatching June 10 in both 1967 and 1968 and continued
for 10 to 15 days. The eggs did not hatch unless they were submerged in
melt water in spring.
Nymphal Development
The nymphs grow rapidly, completing their development to the adult stage
in about one month. Calculated from first hatch to first adults, nymphs
in the Bald Ridge site (elevation 9,185) of the Big Horn Mountains, completed
development in 29 days; while in the Powder River Pass site (elevation
9,660 feet) they completed development in 31 days. In the meadow at Fairbanks,
Alaska, nymphs took 30 to 32 days to become adults.
Adults and Reproduction
In meadows of the Big Horn mountains, adults may appear as early as the
first week of July or as late as the first week of August. They usually
remain in the habitat in which they developed as nymphs and some survive
into mid September. Maturation in nature has not been studied but rearing
of the species in a laboratory at Fairbanks, Alaska has provided information
on this important feature of the adult life history. The adults emerged
between July 10 and August 3; the first mating was observed on July 28
but mating did not become common until August 7. Sexual maturity was attained
about three weeks after molting to adulthood. In laboratory cages mating
usually occurred during the warmest part of the day and pairs remained
in copulo for 10 to 15 minutes. Oviposition began 8 to 10 days after mating
and lasted from mid August until October 1.
No record of females ovipositing in their natural habitat has been made.
Under laboratory conditions females readily oviposit into bare soil. The
pods, 3/4 to 7/8 inch long and slightly curved, contain 12 to 16 eggs (Fig.
10). The egg section is 3/8 inch long and lies in the soil at a depth
equal to the length of the pod. Eggs are two-toned tan and yellow and 4
to 4.8 mm long.
Population Ecology
The northern grasshopper has a history of irrupting in meadows of the Rocky
Mountains. Survey records from the Big Horn Mountains of Wyoming have revealed
populations as dense as 60 young adults per square yard. The species enjoys
a high frequency of occurrence in the many disjunct meadows of the Rocky
Mountains. For example, of 19 meadow sites investigated in 1994 and 1995,
nine harbored individuals of the northern grasshopper and ten were free
of the species (47 percent frequency). Densities of three sites were estimated
to be 20, 8, and 3 young adults per square yard while densities of the
other six occupied sites were all less than 0.1 per square yard. In outbreak
years the species appears to have a higher frequency of occurrence. In
1963, an outbreak year, all of 14 sites surveyed were infested and dominated
by the northern grasshopper. The density of assemblages in these sites
averaged 49 young adult grasshoppers per square yard. We may infer that
the northern grasshopper comprised over half of these densities and it
therefore comprised an average of 25 or more young adults per square yard.
In 1964 the numbers of northern grasshopper were sparse and their dominance
was relinquished to Camnula pellucida and Melanoplus sanguinipes.
Because only limited studies of the population ecology of the northern
grasshopper have been conducted and none for more than three years, we
do not know how many years it takes for populations to increase to outbreak
numbers, nor how long outbreak populations persist after they appear. We
also do not know how long the intervals of low numbers last. Survey data
indicate that an infested site may have high densities in successive years
or due to the biennial life cycle of the species particular sites may have
high numbers one year and low or none the next. Evidently a multiplicity
of physical factors are affecting the growth, survival, and decline of
populations of the northern grasshopper.
Daily Activity
The northern grasshopper dwells chiefly on the ground in meadow habitats
with adequate bare soil for basking. Its nightly refuge has yet to be determined
with certainty. An observation made 10 August 1995 at 7:30 a.m. DST in
a meadow of the Big Horn Mountains (sun hid by clouds, 40° F ground
surface, 50° F air) revealed a female sitting quietly on and parallel
to a dry stem of grass that leaned at a 10° angle to the ground. The
female rested at a height of 2 inches above ground and was sheltered in
a thick midgrass canopy. On clear days grasshoppers leave shelters early
in the morning and move to sunny spots on bare soil or litter to bask.
Observations made in August 1995 from 9 to 11 a.m. DST show that the basking
grasshoppers orient themselves horizontally on the soil surface, turn a
side perpendicular to the sun, and lower the associated hindleg to expose
the abdomen fully to the sun’s rays. On clear days basking ends between
10 and 11 a.m. when ground temperatures have increased to 85° F and
air temperatures exceed 52° F. The grasshoppers may turn on the ground
and face directly away or into the sun and rest, or they may become active--walking,
searching, feeding, and mating. During rains the grasshoppers have been
observed in the Alaskan meadow to take refuge by sitting vertically, head-up
on vegetation. Activity, and much resting, may continue until 5 p.m. at
which time the grasshoppers begin to bask for a second time. Basking then
continues until nearly sunset when they disappear into their nocturnal
shelters.
Selected References
Cantrall, I. J. 1943. The ecology of the Orthoptera and Dermaptera of the
George Reserve. Michigan Misc. Publ. Mus. Zool. Univ. Michigan, No. 54.
Gurney, A. B. and A. R. Brooks. 1959. Grasshoppers of the mexicanus
group, Genus Melanoplus (Orthoptera: Acrididae). Proc. U. S. National Mus.
110: 1-93.
Kreasky, J. B. 1960. Extended diapause in eggs of high-altitude species
of grasshoppers, and a note on food-plant preferences of Melanoplus
bruneri. Annals Entomol. Soc. Amer. 53: 436-438.
Kaufmann, T. 1971. Biology and ecology of Melanoplus borealis
(Orthoptera: Acrididae) in Fairbanks, Alaska with special reference to
feeding habits. Michigan Entomologist 4: 3-13.
Vickery, V. R. And D. K. McE. Kevan. 1985. The grasshoppers, crickets,
and related insects of Canada and adjacent regions. Research Branch Agric.
Canada Publ. 1777.
Larsen, J. C., J. A. Hutchason, T. McNary, and K. Zimmerman. 1988. The
Wyoming grasshopper information system. Coop. Agric. Pest Survey, University
of Wyoming, Laramie.
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