Melanoplus devastator Scudder
Wyoming Agricultural Experiment Station Bulletin 912
Species Fact Sheet
by Robert E. Pfadt
Geographic range of Melanoplus
Click here for the printable version
The devastating grasshopper has a limited geographic range in the
far west of North America. Its main distribution is in the coastal
states, where it inhabits semiarid rangelands dominated by forbs and
annual grasses at elevations from near sea level to over 5,000 feet.
to Top of Page
The devastating grasshopper, a major pest in California and a minor
one in Oregon and Washington, destroys rangeland forage, orchards,
grains, vegetable crops, and gardens. Populations, ever present
on rangeland in the coastal and Sierra Nevada foothills of California,
fluctuate annually in size. Significant damage to rangeland occurs
when densities rise to outbreak levels.
During a prolonged outbreak, more than 3 and 4.5 million acres
of rangeland were infested in 1957 and 1958, respectively. Although
several species were involved, the devastating grasshopper generally
predominated in the assemblages. Forage of the infested rangeland,
often harboring from 35 to 100 devastating grasshopper late nymphs
and adults per square yard, became exhausted. The grasshoppers then
moved to the valleys where green pastures, crops, and gardens flourished.
The hungry marauders defoliated orchards and vineyards and destroyed
fields of barley, corn, beets, vegetables, and many family gardens.
The bark of young fruit trees and grape vines was frequently gnawed
and consumed, killing terminals.
Depredations by this grasshopper have a long history beginning
with the settling of California by the Spanish. Records as early
as 1722 indicate destructive populations. In 1855 immense flights
and severe damage occurred in California, Oregon, and Washington.
The most recent general outbreak took place from 1955 to 1961 with
annual infestations ranging from 580,000 to 4,523,000 acres. Irruptions
since then have occurred on less than 500,000 acres each year.
Live weights of 20-day-old adult males reared from late nymphal
instars averaged 280 mg and of females 341 mg (dry weights 103 mg
and 125 mg, respectively). The nymphs were collected from a population
inhabiting Jasper Ridge, Palo Alto, California on 5 July 1993 and
reared on dandelion.
to Top of Page
The devastating grasshopper, a polyphagous insect, consumes a variety
of grasses, forbs, shrubs, and trees. Under favorable spring conditions
in their natural rangeland habitat, the nymphs feed preferentially
upon various legumes, filaree, and brome and barley grasses. When
these plants mature and become dry, late nymphs and adults survive
on green but less palatable plants such as needlegrass, Stipa
spp., tarweeds, Hemizonia spp. and wild lettuce, Lactuca
spp. Favorite items of food at these times are grass seeds shed
naturally or dropped by harvester ants (Messor andrei) on
their mounds. The late nymphs and adults have been observed feeding
on the epidermis of stems of the less palatable plants and on the
edges of leaves. They may reject other drought-resistant plants
that commonly grow in their habitat, such as turkey mullein. They
also feed on stubble and ground litter. Late nymphs assume various
orientations in feeding. Two common orientations are a nearly vertical
head down position as they feed on epidermis of stems and a horizontal
position on the ground as they feed on litter.
After rains start in fall and growth of preferred host plants begins
anew, the adults mature and reproduce. Many observations have been
made of the damage caused by the migrating swarms. Migrants have
been observed to feed on the leaves of grape, citrus, apple, pear,
cherry, peach, apricot, prune, plum, almond, avocado, and also on
cabbage, tomato, beet, beans, marigold, alfalfa, clover, timothy,
corn, and barley. The list is undoubtedly incomplete and could be
lengthened considerably from experiences of California growers,
entomologists, and horticulturists.
to Top of Page
Figures 1-6. Appearance
of the six nymphal instars, their sizes, structures, and color
patterns. Notice progressive development of wing pads. BL=body
length, FL=Hind Femur Length. AS=number of antennal segments
First Instar: BL 3.4-4.6 mm FL 2-2.1 mm AS 13.
Second Instar: BL 4.8-6.6
mm FL 2.6-2.9 mm AS 14-16.
Third Instar: BL 5.9-6.8 mm FL 3.6-5.2 mm ASl 17.
Fourth Instar: BL 10.5-12.5 mm FL 6.1-6.7 mm AS
Fifth Instar: BLl 13-15.2 mm FL 8.4-8.9 mm AS 22-23.
Sixth Instar: BL 15-19.5 mm FL 9.5-11.7 mm
Figures 7-10. Appearance
of the adult male and female, cercus, and egg pod.
Adult Male: BL 18.5-22 mm FL 10.3-11.5 mm AS 25-26.
Adult Female: BL 21-23 mm FL 12-13.5 mm AS 25-26.
Side view of end of male abdomen.
Egg pod and group of exposed eggs.
The devastating grasshopper is a medium-sized grasshopper with
long wings that extend beyond the end of the abdomen (Fig. 7 and
8). Along with the migratory grasshopper, it is a member of the
mexicanus group of the genus Melanoplus. The males
have two diagnostic characters that distinguish this species from
the migratory grasshopper, which it resembles. The cerci are elongated
and slender; the furculae are long, extending halfway on the supraanal
plate (Fig. 9).
Both males and females of the devastating grasshopper share several
characteristics. The body color is pale gray and tan with fuscous
maculations; the venter of the abdomen is pale greenish yellow.
The tegmen is marked by a row of conspicuous black spots (Fig. 7).
The color pattern of the medial area of the hind femur consists
of pale or reddish tan and fuscous patches. The hind tibiae are
usually blue but may be red. In the Jasper Ridge, California site,
3 percent of males and 15 percent of females have red hind tibiae.
The nymphs are identifiable by their structure and color patterns
- Head with face nearly vertical; antennae filiform, compound
eyes brown with irregular ivory spots and occasional dark spots;
a broad, ivory, or pale tan crescent begins on gena below compound
eye and extends onto side of pronotum.
- Hind femur with narrow dark stripe in center of medial area
in instars I and II; in instars III to VI dark stripe cut in middle
by wide (approximately two chevrons wide), diagonal, pale tan
bar; a large pale tan patch interrupts the dark stripe at base
of medial area.
- General body color pale yellow, pale tan, or pale green.
Although the nymphs of the devastating grasshopper closely resemble
those of the migratory grasshopper, they can be separated by differences
in several characters that can be seen with either the naked eye
or a 10x magnifier. Instar I of the devastating grasshopper is pale,
has the ivory crescent clearly evident, and the medial area of the
hind femur is pale yellow with a narrow dark stripe running down
the middle. Instar I of the migratory grasshopper is dark with many
fuscous spots, the crescent is faint, and the medial area of the
hind femur is marked heavily with fuscous spots that partially conceal
the dark stripe.
Two characters are useful in separating instars II-VI. The compound
eyes of devastating grasshopper nymphs lack a diagonal dark bar,
which is present in compound eyes of the nymphs of the migratory
grasshopper. The medial area of the hind femur of the devastating
grasshopper has the dark stripe interrupted by large ivory patches,
while that of the migratory grasshopper has smaller light patches.
(See illustrations of nymphs of the two species.)
Recent genetic studies of the two species suggest that M. sanguinipes
and M. devastator are closely related and may be the same
species or at least subspecies. However, because of clear structural,
life history, and geographic differences, taxonomists continue to
regard the two as related but separate species. Despite the controversy
over species definition, the ecology and bionomics of the migratory
and the devastating grasshoppers differ substantially. In California,
the migratory grasshopper breeds and becomes a minor problem in
irrigated alfalfa and permanent pastures (improved and irrigated),
while the devastating grasshopper breeds in foothill rangelands
and becomes a major problem when bands and swarms migrate into cropland.
to Top of Page
When populations irrupt and rangeland forage becomes depleted,
the devastating grasshopper becomes a highly migratory insect. Bands
of older nymphs crawl and hop while swarms of adults fly to the
valleys. Nymphs usually migrate downhill toward more succulent green
vegetation. They follow ravines and drainages toward cultivated
crops, often migrating 5 miles or more during this stage. Extensive
movements of nymphs took place in Alameda and Butte counties in
California on 13 June 1957 when grass had dried on the hillsides
but swales were still green.
Adult migrations are less predictable and may be delayed. Between
25 July and 8 August 1957, a spectacular migration of adults occurred
from the California Range Experiment Station at Hopland. Adults
are strong fliers and swarms migrate 15 or more miles in a single
day. In this stage they have been observed to travel a distance
of at least 30 miles. Attractive landing sites are fields of yellow
stubble of barley, oats, and wheat. From these fields the devastating
grasshopper disperses to fruit and vegetable crops. Even though
the major pest status of this grasshopper results from its migrations,
no special study of this behavior has been made. Some entomologists
speculate that every year a part of each population migrates, but
the migrants usually go unnoticed because of small numbers.
When flushed, nonmigratory adults travel 3 to 6 feet at heights
of 4 to 12 inches. Their flight is straight and silent; however,
flight noise or crepitation was heard once in San Mateo County,
to Top of Page
The hatching period, which ranges from 50 to 103 days, starts in
late April and may extend to late July. This is a prolonged hatching
period compared to that of several other species (e.g., Camnula
pellucida and Oedaleonotus enigma) that occur in assemblages
of California rangeland grasshoppers. The difference is probably
due in part to the lateness of oviposition and greater depth of
the eggs in the soil of the devastating grasshopper. The total heat
units required for development and hatching of the eggs of all three
species are probably similar.
to Top of Page
The nymphs begin development when forage is green and succulent
but a majority are often in the nymphal stage (instars IV, V, and
VI) when the forage has matured and dried. Nutritional stress evidently
prolongs the nymphal period as some nymphs may still be found in
mid October. Both males and females require six instars to complete
their nymphal development. The first nymphs that appear during the
last week of April may become adult by July 1. This means that precocious
adults take about 70 days to reach the fledgling stage.
to Top of Page
Among rangeland species, the devastating grasshopper has a unique
life history. Females enter a reproductive diapause during the summer
months and must survive on less palatable forage to tide them over
to the reproductive period, which begins in late September. Laboratory
experiments have shown that development and maturation of eggs within
the females are triggered by decreasing day length. Usually fall
rains arrive at this time, stimulating sprouting and growth of preferred
food plants. The usual coincidence of the breaking of reproductive
diapause and the availability of nutritious host plants allows the
females to oviposit prolifically. Dissection of females collected
at the Hopland Range Experiment Station in Mendocino County, California
and at Mission Peak study area in Alameda County, California, revealed
that mature eggs were present in the ovaries at the end of September
and in October, 1963.
The females oviposit in restricted locations within their normal
rangeland habitat. They prefer well-drained hillocks, ridges, slopes,
and banks of ravines where soil is gravelly. Many pods are deposited
within relatively small areas (egg beds). Only a few pods are deposited
in surrounding soil. Pods are deposited close to the basal growth
of forbs such as tarweeds and Russian thistle. Some are laid among
the roots of filaree or in small, well-drained bare spots. Pods
are 3/4 to 7/8 inch long, slightly curved, and contain 20-31 eggs
(Fig. 10). The eggs are pale yellow and 3.9-4.4 mm long.
No study of courtship of the sexes has been made nor is it known
whether the males, like the females, have a reproductive diapause.
to Top of Page
In their natural rangeland habitats in the foothills of the coastal
states, populations of the devastating grasshopper persist over
many years. Astonishingly large changes in densities occur with
time. Grasshoppers may increase from noneconomic numbers to as many
as 100 per square yard in just three years. Before the severe outbreak
of 1957-58, survey entomologists began to notice increases in densities
in the Sierra Nevada foothills in 1952. In 1953 and 1954 the sizes
of populations were rated about the same as in 1952, but in 1955
the densities of populations increased dramatically and the economically
infested acres expanded by five fold, from 220,000 acres in 1954
to 1,264,000 acres in 1955. The sudden increases in both densities
and infested acreage suggest that populations had experienced especially
favorable conditions for growth. Although populations grew at a
slower rate during the next three years, they continued to increase.
Two other species, Oedaleonotus enigma and Camnula pellucida,
contributed to the outbreak, but the devastating grasshopper was
the primary pest. In 1959 a fungal disease (Entomophaga grylli)
killed many grasshoppers, reducing some populations by as much as
90 percent. The disease and a subsequent drought led to a gradual
decline of the outbreak during the next six years.
Like other rangeland grasshopper assemblages, those in the foothills
of California consist of several species. The devastating grasshopper
often dominates and coexists with O. enigma, C. pellucida,
Dissosteira pictipennis, and several other species. In habitats
less favorable for the devastating grasshopper, other species may
dominate. In montane grasslands C. pellucida usually dominates,
while in valley and low foothill habitats O. enigma often
dominates. Migrants of the devastating grasshopper that invade crops
do not successfully colonize these valley habitats, but the reason
for this is unknown.
to Top of Page
Behavior of the late nymphs and young adults was observed on Jasper
Ridge in a serpentine grassland habitat from the 3 to 5 July 1993.
The ridge is a low-lying foothill (maximum elevation 620 feet) on
the eastern side of the Santa Cruz mountains with a Mediterranean-type
climate. Skies are generally clear and virtually no rains fall during
the nymphal development of the devastating grasshopper. Sampling
of the resident population of devastating grasshoppers indicated
a density of eight per square yard (late nymphs and young adults).
In early July, ground temperatures during the night fall to 60°F
and air temperatures to 50°F. Approximately one hour after sunrise
the grasshoppers begin to move from overnight retreats and crawl
to sunny spots to bask. Some crawl up stems of dead weeds or culms
of grasses, while others stay on the ground. They turn a side perpendicular
to the rays of the sun and lower the associated hindleg to expose
the abdomen fully to the warming rays. They bask for a period of
two hours from 7 to 9 a.m. DST. However, feeding may start as early
as 8 a.m., and feeding of different individuals may be observed
for two or more hours.
The feeding period ends when rapidly increasing temperatures of
the habitat force them to take evasive actions. By mid morning,
surface temperatures of the black, gravelly serpentine soils rise
to over 130°F and later exceed 160°F. To avoid high ground temperatures
the grasshoppers climb forb stems and grass culms and rest vertically
head-up in the shade at heights of 2 to 9 inches. When temperatures
moderate in late afternoon (5 p.m. DST), the grasshoppers feed again.
This second period of feeding lasts for approximately two hours.
The grasshoppers have no second daily period of basking. After feeding
they seek shelter under canopies of vegetation and may back into
small depressions. They begin this movement as early as 7 p.m. when
ground surface temperatures are in the 80s and air temperatures
are 67° to 71°F.
to Top of Page
Cooperative Economic Insect Report 1952-1975. USDA
APHIS PPQ. Vol. 2-25.
Cooperative Plant Pest Report 1976-1980. USDA APHIS
PPQ. Vol. 1-5.
Middlekauff, W. W. 1964. Effects of photoperiod
upon ö genesis in Melanoplus devastator
Scudder (Orthoptera: Acrididae). J. Kansas Entomol. Soc. 37: 163-168.
Orr, M. R., A. H. Porter, T. A. Mousseau, and H.
Dingle. 1994. Molecular and morphological evidence for hybridization
between two ecologically distinct grasshoppers (Melanoplus sanguinipes
and M. devastator) in California. Heredity 72: 42-54.
Rentz, D. C. F. and D. B. Weissman. 1981. Faunal
affinities, systematics, and bionomics of the Orthoptera of the
California Channel Islands. Univ. California Publ. 94: 1-240.
Weissman, D. B. and D. C. F. Rentz. The Orthoptera
of Stanford University's Jasper Ridge and neighboring Palo Alto,
California. Wasmann J. Biol. 35: 87-114.
Wilson, C. C. 1947. Control of the devastating
grasshopper in California. Bull. California State Dept. Agric. 36(3):
to Top of Page