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Montana Field Guide

Montana Field Guides

Striped Slant-faced Grasshopper - Amphitornus coloradus

Native Species

Global Rank: G5
State Rank: SNR


Agency Status
USFWS:
USFS:
BLM:



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General Description
The following comes from Hebard (1928), Brooks (1958), Helfer (1971), Otte (1981), Capinera and Sechrist (1982), Vickery and Kevan (1985), McDaniel (1987), Pfadt (2002), Capinera et al. (2004), and Scott (2010). Medium-sized, brownish-yellow or green grasshopper. Two dark brown stripes run from the top of the head and broadening across the pronotum and fading onto the wings (tegmina). The hind tibia is blue. The face is strongly slanted, and the antennae are flattened.

Phenology
Overwinters in the egg stage. Eggs hatch at the end of May or early June. Adults occur from late-June to early-October (Capinera et al. 2004, Capinera and Sechrist 1982, Otte 1984, Pfadt 2002, Schell et al. 2005, Scott 2010, and Vickery and Kevan 1985).

Diagnostic Characteristics
The following is taken from Hebard (1928), Brooks (1958), Helfer (1971), Otte (1981), Capinera and Sechrist (1982), Vickery and Kevan (1985), McDaniel (1987), Pfadt (2002), Capinera et al. (2004), and Scott (2010). Adult body length for males is 18 to 20 mm, and females 21 to 25 mm. Hind femur has three dark bands on the upper outer surface. Junction of femur knee with the tibia is black. Wings (tegmina) are unspotted with a white stripe on the lower basal third.

Could be confused with similarly marked slantfaced species in the genera Cordillacris, Opeia, Mermiria, or Psuedopomala. Closely observe diagnostic characteristics for positive identification.

Species Range
Montana Range Range Descriptions

Native
 


Range Comments
Widely distributed across the grasslands of North America, from the western provinces of Canada, southward into central Mexico, and westward from western Illinois to Washington, Oregon, and California. In Montana, this species has been recorded for 49 counties, but likely occurs in suitable grassland habitats throughout the state (Brooks 1958, Capinera et al. 2004, Capinera and Sechrist 1982, Otte 1984, Pfadt 2002, Schell et al. 2005, Scott 2010, and Vickery and Kevan 1985).

Observations in Montana Natural Heritage Program Database
Number of Observations: 25

(Click on the following maps and charts to see full sized version) Map Help and Descriptions
Relative Density

Recency

 

(Observations spanning multiple months or years are excluded from time charts)



Habitat
Prefers mixed-grass and bunchgrass prairies. Also inhabits dry, grassy slopes and small, grassy spots along river valleys. Often clings to grasses and never seen walking over open ground. Usually occurs at elevations below 7600 feet, but accidentals have been collected as high as 11,400 feet (Capinera et al. 2004, Capinera and Sechrist 1982, Otte 1984, Pfadt 2002).

Food Habits
The Striped Slant-faced feed almost exclusively on grasses and sedges, favoring blue gramma (Bouteloua gracilis), needle-and-thread (Stipa comata), thread-leaved sedge (Carex filifolia) and needleleaf sedge (Carex duriuscula). Seventeen other grass species have been reported consumed, as well as some forbs (Capinera and Sechrist 1982, Pfadt 2002, Schell et al. 2005).

Reproductive Characteristics
Males stridulate before making a copulatory leap on the female. The female selects a needle-and-thread (Stipa comata) or a thread-leaved sedge (Carex filifolia) in which to oviposit her eggs. She deposits four eggs on the plant stem and forms a pod just below the soil surface. The outer wall of the pod is constructed of dry fragments of grass and soil particles. The nymphs pass through 5 instars before reaching the adult stage in 50 to 56 days (Capinera and Sechrist 1982, Pfadt 2002, Schell et al. 2005).

Management
The Striped Slant-faced Grasshopper can cause damage to rangelands and native grasslands. Among the assemblages of grasshoppers infesting rangelands, it is rarely the dominate species but can be the third most abundant (Pfadt 2002, Schell et al. 2005).

References
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Citation for data on this website:
Striped Slant-faced Grasshopper — Amphitornus coloradus.  Montana Field Guide.  .  Retrieved on , from