Wyoming distribution map
The Gladston grasshopper ranges widely in the rangelands of western North America. It inhabits the mixedgrass, shortgrass, tallgrass, bunchgrass, desert, and sand prairies and also lives in grass-shrub habitats of the intermountain basins. It is a common species in the grasslands east of the Rocky Mountains and is also present in the foothills and mountain parks as high as 8,500 feet.
A dietary study of grasshoppers inhabiting alfalfa fields in North Dakota revealed that the Gladston grasshopper ingested plants in direct proportion to their abundance. Crop contents consisted of 75 percent alfalfa, 14 percent kochia, 10 percent smooth brome, and smaller amounts of nine less common plant species.
Several direct observations of the method of feeding of this grasshopper have been made at a study site of the mixedgrass prairie of eastern Wyoming. Adults attracted to isolated plants of Russian thistle climbed the plants and, from various orientations, fed upon the growing tips, small leaves, and especially the developing seeds, which were soft and juicy. A female was observed to crawl up an unidentified forb and feed, vertical, head up, on the edges of the green leaves. A female in a horizontal position on the ground was observed feeding on plant litter, and another female fed on a dead female grasshopper, Trachyrhachys kiowa.
An interesting observation was made of two adult Gladston grasshoppers that had moved from adjacent mixedgrass prairie into a winter wheat field during late October 1992. The wheat was 6 to 8 inches tall, but the first 16 rows had been eaten by grasshoppers that had migrated from the adjacent mixedgrass prairie, and only green stubs of wheat remained in these rows. One female Gladston grasshopper, horizontal on the ground, was observed feeding on the cut end of a green wheat stub. A male on the ground was observed feeding in the middle of a recumbent wheat leaf. This grasshopper chewed intermittently on the leaf with a peculiar up and down motion of its head. Close inspection of the leaf revealed that it was not being consumed but only chewed. Probably the grasshopper was seeking moisture but ingesting some leaf tissue.
Mass migration into Cheyenne, Wyoming became apparent during the last week of August 1991, when hundreds of young adults were seen on asphalt and concrete, in downtown doorways, and in grassy lots. Further evidence of mass migration was deduced from results of sampling densities of grasshoppers in the mixedgrass prairie of eastern Wyoming (Platte County). A population of late instars and adults declined suddenly from 0.7 to 0.2 per square yard between August 13 and 26, 1969. During the same interval no decline in the migratory grasshopper, Melanoplus sanguinipes, occurred. This fact implied that no epizootic, intensive predation, or other severe mortality factor was present on the site. The previous year, survival of the Gladston grasshopper was high in August. Only a 2 percent per day mortality occurred in 1968, while in 1969 the decrease due to the apparent mass emigration amounted to 11 percent per day.
Flushed flights range from 2 to 9 feet at heights of 4 to 8 inches. The flight is silent and usually straight, but occasionally curved. The grasshopper lands face away from the intruder.
The nymphs are identifiable by their structures, color, and shape (Fig. 1-5).
1. Head with face nearly vertical; frontal ridge either light or fuscous; frontal view of lower mouthparts fuscous or black. Antennae filiform and fuscous dorsally, each segment ringed anteriorly in ivory. Compound eye brown with many light spots; a diagonal dark bar crosses middle.
2. A distinct yellow or ivory crescent begins on gena below compound eye and runs onto lateral lobe of pronotum. Dorsal stripe of hind femur interrupted in middle by light patch. Hind tibia pale yellow or pale gray in instars I to IV; pale blue in instar V; front edge fuscous.
3. Body color pale gray and light brown marked with fuscous; bottom of thorax and abdomen usually bright yellow but in a few specimens pale yellow or olive.
Many of the described nymphal characters of M. gladstoni, M. infantilis, and M. occidentalis are similar, yet nymphs of these species can be separated easily by color and by their seasonal appearance. The venter (ventral side of both thorax and abdomen) of nymphs of the Gladston grasshopper is usually bright yellow, while the venter of nymphs of M. infantilis is usually white and of M. occidentalis pale gray. Nymphs of M. infantilis and M. occidentalis are present in the grasshopper assemblage early in the season along with nymphs of M. sanguinipes and M. packardii, while those of the Gladston grasshopper are present late when all four of the former species are adults.
Oviposition has not been observed, but females confined in a laboratory terrarium with sandy loam soil and sod in the center laid in the bare soil, which was interspersed in the sod, and in the peripheral soil. Pods are 1 to 1 1/8 inches long and notably curved (Fig. 10) and contain 16 to 29 eggs. The eggs are tan and 4 to 4.9 mm long. Eggs are contained in the bottom section of the pod and because of its diagonal orientation, the eggs lie in the soil at a depth between 5/16 to 10/16 inch. The top section of pod consists of dry froth.
In the shortgrass prairie of northeastern Colorado, the Gladston grasshopper is a principal member of the assemblage. It may range from less than 0.1 to 1.1 per square yard. The latter number is reached during a peak in density of the assemblage (Table 1). From 1980 to 1985 populations of the Gladston grasshopper at this site fluctuated between 0.1 and 1.1 individuals per square yard, making it the primary or secondary species in five of the six years.
Early in the morning before the rays of the sun strike them, the grasshoppers emerge from their nighttime shelters. They rest horizontally on the ground facing in various directions. When the rays eventually reach them, about one hour after sunrise, they begin to bask by turning a side perpendicular to the rays and by lowering the hindleg to maximize exposure of the abdomen. They bask from one to two hours at soil temperatures that range from 59° to 103°F and air temperatures (1 inch high) from 59° to 76°F. Some individuals, however, become active at a soil temperature of 85° and an air temperature of 65°F. The peak of activity comes between 10 a.m. and noon, at which time they feed, mate, and walk about on the ground. When temperatures rise above their tolerance level, they cease activity and take evasive actions. First they may face the sun or face directly away and stilt; as temperatures increase they climb vegetation to heights of 4 inches or more.
They again bask in the afternoon from 4 to 7 p.m. on bare soil. When shadows engulf these spots, they crawl into their nighttime shelters under canopies of grasses, usually blue grama.
Capinera, J. L. and D. C. Thompson. 1987. Dynamics and structure of grasshopper assemblages in shortgrass prairie. Can. Entomol. 119: 567-575.
Fry, B., A Joern, and P.L. Parker. 1978. Grasshopper food web analysis: use of carbon isotope ratios to examine feeding relationships among terrestrial herbivores. Ecology 59: 498-506.
Joern, A. 1982. Distributions, densities, and relative abundances of grasshoppers (Orthoptera: Acrididae) in a Nebraska sandhills prairie. Prairie Naturalist 14: 37-45.
Mulkern, G. B., J. F. Anderson, and M. A. Brusven. 1962. Biology and ecology of North Dakota Grasshoppers, I. Food habits and preferences of grasshoppers associated with alfalfa fields. North Dakota Agr. Exp. Stn. Research Report No. 7.
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.
Newton, R. C., C. O. Esselbaugh, G. T. York, and H. W. Prescott. 1954. Seasonal development of range grasshoppers as related to control. USDA Bureau Entomol. Plant Quarantine E-873.
Pfadt, R. E. and R. J. Lavigne. 1982. Food habits of grasshoppers inhabiting the Pawnee site. Wyoming Agr. Exp. Stn. Science Monograph 42.
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