Wyoming distribution map
The differential grasshopper, Melanoplus differentialis (Thomas), ranges widely in North America. Originally restricted to tall herbaceous vegetation growing in wet meadows, swales, and creek bottom lands, the species spread into the weedy vegetation of crop borders, roadsides, and reversions brought about by settlement and agricultural development. In the United States large populations develop in extensive areas of cropland located between the Rocky Mountains and the Mississippi River. Populations east and west of these landmarks are spotty and discontinuous.
Adults display strong powers of flight. In search for green food, they may move upwind in short, low flights of 10 to 100 yards toward green corn. These flights begin around 9 a.m. and reach a peak when temperatures rise to 81°F.
Flight also provides escape from extreme heat of temperatures above 86°F. Grasshoppers rise and mill about in calm air or fly with the wind. They have been seen by airplane pilots as high as 1,400 feet above the ground, but most have been seen below 600 feet. In 1939 the differential grasshopper migrated northward by successive short flights from along the Missouri River in southeastern South Dakota to as far north as Pierre, South Dakota, a distance of 130 miles. In North Dakota one differential grasshopper of a marked group was recovered 20 miles from the point of release two days after its liberation. During outbreaks of this species adults have longer wings and slimmer bodies.
The adult male (Fig. 7) is identifiable by the shape of the cercus (Fig. 9) and both male and female by the black chevrons on the hind femur. A melanistic female is pictured in Figure 8. The majority of females are yellow with black markings like the male shown in Figure 7.
The nymphs (Fig. 1-6) are identifiable by their spots, stripes, and color patterns:
(1) Compound eye brown with light tan spots; lacking transverse dark band.
(2) Front of head green, yellow, or tan often with dark spots and a few larger markings.
(3) Pronotum with pale yellow, horizontal stripe at top of lateral lobe; brown band at edge of pronotal disk; narrow, median pale yellow stripe on pronotum, mesonotum, metanotum, and continuing on to abdomen various distances.
(4) Gena with short, pale yellow band below compound eye and continuous with pale yellow stripe of lateral lobe. Band faint or lacking in fifth and sixth instars.
(5) Black stripe of hind femur occupying center of medial area in first to fourth instars; black chevrons beginning to be evident in fifth and sixth instars. Black stripe in first instar often interrupted by pale band.
(6) Hind tibia light green or light gray to gray.
(7) General color pale green, pale yellow, or tan; many fuscous markings.
Egg pods of the differential grasshopper are curved, one and one-half inches long and one-quarter inch in diameter. They are fragile and easily broken in sifting them from the soil. The eggs are olive and 4.4 to 5.1 mm long. In separate laboratory experiments, females fed a single plant diet of soybeans averaged 305 eggs each while those fed common sunflower averaged 591 eggs each. The maximum number of eggs deposited by a single female fed soybean was 645 and the maximum number of pods was six. The number of eggs laid by females in nature is unknown. There is one generation annually.
The high biotic potential of the differential grasshopper is evident in the records of an outbreak that occurred more than 50 years ago in Missouri. In 1934 the differential grasshopper was present in noneconomic numbers. In 1935 this species became more numerous, damaging fall wheat and alfalfa. The warm, dry summer and fall of 1935 provided favorable conditions for egg production. The next year, 1936, spring rains and warm temperatures allowed a successful hatch and nymphal development that precipitated the worst outbreak of grasshoppers in Missouri since the years of the Rocky Mountain locust. Favorable weather continued and allowed the differential grasshopper to stay at outbreak numbers in 1937; the fall egg survey that year showed the greatest density of eggs ever. In 1937 the eggs hatched but this period was followed by rains and cool weather. The emerged nymphs died ending the outbreak.
Like the nymphs the adults rest high on plants at night and descend only when temperatures are 68°F or above and the sun rises and strikes both them and the ground. Upon descending they begin to feed. Feeding slackens at 86°F and ceases at air temperatures above 90°F and soil surface temperatures above 112°F. At these high temperatures, air 86° to 90°F, adults seek shade or rise in flight. Table 1 summarizes information on the influence of temperature upon activities of nymphs and adults.
Kaufmann, T. 1968. A laboratory study of feeding habits of Melanoplus differentialis in Maryland (Orthoptera: Acrididae). Ann. Entomol. Soc. Am. 61: 173-180.
Lewis, A. C. 1984. Plant quality and grasshopper feeding: effects of sunflower condition on preference and performance in Melanoplus differentialis. Ecology 65: 836-843.
Munro, J. A. and S. Saugstad. 1938. Grasshopper migration in North Dakota. North Dakota Agric. Exp. Stn. Bimonthly Bull. 1(1): 4-5.
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.
Sanderson, M. W. 1939. Crop replacement in relation to grasshopper abundance. J. Econ. Entomol. 32: 484-486.
Slifer, E. H. 1932. Insect development IV. External morphology of grasshopper embryos of known age and with a known temperature history. J. Morphol. 53: 1-21.
Swenk, M. H. and C. H. Bratt. 1941. The relation of temperature to the embryonic and nymphal development of the differential grasshopper Melanoplus differentialis Thomas. Nebraska Agric. Exp. Stn. Res. Bull. 122.
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