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The slantfaced pasture grasshopper ranges widely in North American grasslands from east of the Rocky Mountains to the Atlantic Coast and from southern Canada to northern Mexico. The species is most abundant in upland areas of short grasses in the tallgrass and southern mixedgrass prairies. In the shortgrass prairie of Colorado and New Mexico, it inhabits mesic swales. Generally preferring mesic habitats, its center of distribution appears to be in the tallgrass prairie where its populations often become numerically dominant. In eastern states this grasshopper occurs principally in relatively dry upland and hilly pastures with sandy loam soil and often becomes abundant and the dominant species.
In a small patch of short grass within the tallgrass prairie of Comanche County, Kansas, two observations were made of method of feeding. On 24 August 1997 at 10:30 a.m. DST (temperature 1 inch above the ground was 79°), a pair in copulo hopped onto the top of blue grama and landed horizontally. After five minutes of basking, the female cut through a leaf, held onto the detached portion, and began to feed on the cut end. She fed briefly, crawled a short distance on top of the grass, and began to bask again. A second female was discovered resting horizontally on the top of a blue grama plant, stirred and oriented itself diagonally, and then began to feed on the tip of a leaf.
Because of the scant number of observations of feeding in nature, several observations were made in a terrarium stocked with turf of blue grama, western wheatgrass, and bare soil. Adults jumped or climbed onto the blue grama and fed vertically, head-up on the edge of a leaf, and moved up the leaf ingesting about 1/8 inch of leaf edge at a time. Thin edges of the attacked leaves were left standing. In another cage a female jumped onto the base of an 8-inch green leaf of downy brome and began to feed from a vertical head-up position on the edge of the leaf. Eating upward on the leaf, the grasshopper continued feeding for 18 minutes and then ceased. During this time the female consumed green leaf tissue 2 3/8 inches long by 1/8 inch deep and caused a gouge in the leaf of these same dimensions. A residual edge of 1/8 inch width was left standing. Occasionally a leaf was cut through; the grasshopper held onto the detached section with the front tarsi, eating the green material completely and dropping the yellow, dry tip. Adults were also observed to feed head-down on leaf edges.
Flushed flight is silent, often straight, but sometimes circular, for distances of 1 to 4 feet and usually at heights of 4 to 12 inches. Flushed flight, however, may be as high as 5 feet (1 of 16 observations). Flights were chiefly crosswind but one was into a variable wind that ranged from 3 to 10 mph.Fig. 6 and 7). Specimens are usually spotted and marked with brown and black. Some individuals bear much green while others are entirely tan and brown. The face is strongly slanted. The antennae are filiform. Compound eyes are tan with fuscous spots and markings. Behind each eye on the side of the head is a broad fuscous band, above it a thin black line, and above the latter a light line often colored ivory. A second species, Orphulella pelidna, inhabits the prairies east of the Rocky Mountains in greater abundance than 0. speciosa. The two species can be distinguished from one another by structural differences. The slantfaced pasture grasshopper, 0. speciosa, has a small semicircular depression of the vertex that is closer to the front and the lateral carinae of the pronotum incised once (Fig. 8 and Fig. 10). 0. pelidna, a larger species, has a larger semicircular depression set farther back and the lateral carinae incised twice, occasionally three times (Fig. 10).
The nymphs are identifiable by their shape, structures, and color patterns (Fig. 1-5).
1 . Head. Compound eyes tan and spotted brown; face strongly slanted; antennae of instar I terminally expanded, antennae of instar II flat and terminally pointed, antennae of instars III to V filiform; semicircular depression of vertex located close to front of fastigium; head of instars I and II with patterns of green, of instars III to V with patterns of tan, brown, green, and fuscous.
2. Lateral carinae of pronotum incised once, colored ivory, sometimes green on metazona in older instars; hind femur with medial and upper marginal areas of instars I and II tan, of instars III to V fuscous; lower part of medial area and lower marginal area pale gray. Thorax of instars I and II with patterns of green, of instars III to V patterns of tan, brown, green, and fuscous.
3. Abdomen in instars I and II green with darker green band on each side that runs forward on lateral lobe and side of head to eye, in instars III to V the lateral band is fuscous.
Courtship of females by males was observed on the George Reserve, Michigan and in Southwestern Quebec. Males may court females by stridulating, making a faint ticking sound, repeated three to ten times. Males stalk moving females slowly and stealthily and when close enough, pounce on them without signaling. After the pair coupled, any disturbance or stirring of the female induces the male to stridulate, which keeps the mating pair together. In Comanche County, Kansas, 23-25 August 1997, pairs in copulo were observed from 9:22 a.m. to 2:20 P.M. (the time limits of the observations). The grasshoppers appeared to be in a mating frenzy. Of 60 grasshoppers observed 18 were of single individuals and 21 were of copulating pairs.
Oviposition has not been observed in nature. A clue to location of pods was obtained in a laboratory terrarium furnished with buffalograss turf and bare soil. Three females deposited six pods in the small bare spaces between grass plants and none in the large bare areas. None of the pods was attached to roots of the grass. This location of pods among shortgrass plants would make the discovery of ovipositing females in nature difficult. The pods measure 13/16 inch long and contain from 10 to 13 eggs each (Fig. 9). Eggs measure 3.5 to 4.1 mm long and are pale yellow when laid becoming brown as they age. The eggs are deposited in summer, overwinter, and hatch the following year in late spring.
That this grasshopper prefers to inhabit sites of short grass was evident in grassland of Comanche County, Kansas. On 25 August 1997 a population inhabiting a 300 square foot patch of blue grama and buffalograss reached 14 adults per square yard. In surrounding tallgrass the adults numbered less than one per square yard. The predominant tall grasses were interspersed with other patches of short grasses, which were also populated abundantly with adults of the slantfaced pasture grasshopper. In Oklahoma and South Dakota, entomologists have observed the dispersal of large numbers of adults into freshly mowed roadsides. These tracts of land bear not only shorter, but also greener and more succulent vegetation.
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Wilbur, D. A. and R. F. Fritz. 1940. Grasshopper populations (Orthoptera, Acrididae) of typical pastures in the bluestem region of Kansas. J. Kansas Entomol. Sec. 13: 86-100.