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Montana Field Guide

Montana Field Guides

Great Grig - Cyphoderris monstrosa

Native Species

Global Rank: G5
State Rank: SNR

Agency Status


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General Description
The following is taken from Hebard (1928), Helfer (1971), Morris and Gwynne (1978), Vickery and Kevan (1985), Capinera et al. (2004), and Scott (2010). The genus Cyphoderris is represented by two species in Montana, the Great Grig (C. monstrosa) and the Buckell’s Grig (C. buckelli). They are short-winged (tegmina) and flightless. The female wings are reduced to small oval lobes, and male wings are well developed for loud stridulation (“singing”). The Hump-wing Grigs are small to medium sized, robust, and bear similar body colors with contrasting black markings.

As in Crickets, the Grylloidae, stridulation is performed only by males and is generated by scraping one wing over the other. Unlike male crickets, which generally have the right wing with a scraper overlapping the top of the left wing with a file, the Grig’s wings are mirror images with both wings bearing a functional file and scraper. Thus, Cyphoderris males are able to change their wing overlap positions where both wing files are used in its singing, which produces a variation in their song’s intensity and frequency. This suggests that such changes are the result of irregular switching of the wings from top to bottom positions, a habit referred to as “switch-wing singing,” and occurs several times in the course of a single trill. In the field, the night songs of both Cyphoderris species are almost indistinguishable. The song of C. monstrosa has been described as “a loud, penetrating, high-pitched, shrill, metallic trill repeated at rates of 15 to 20 per minute (Spooner 1973). However, song rates are subject to rising and declining due to ambient temperature or courtship calling. Grig species are known for their singing activity at much lower temperatures than that of other Ensifera species (suborder of katydids and crickets). For more detail and acoustical sonograms of these behaviorally complex species, refer to the papers by Fulton (1930), Spooner (1973), Morris and Gwynne (1978), Morris et al. (2002).

All Cyphoderris species are believed to overwinter concealed as a nymph, emerging in late spring to early summer when they become an adult in June, and remain active to November or the onset of cold weather (Morris and Gwynne 1978, Vickery and Kevan 1985, and Scott 2010).

Diagnostic Characteristics
The following comes from Hebard (1928), Helfer (1971), Morris and Gwynne (1978), Vickery and Kevan (1985), Capinera et al. (2004), and Scott (2010). The body length for males and females of this species is 20 mm to 30 mm (C. monstrosa) tends to be larger than its congener, C. buckelli. Both sexes possess the Ander’s organ, a reddish ridged patch on the dorsolateral side of the first abdominal segment (see illustration). The male genitalia has a prominent ventrally-directed sternal process shaped like the claw of a hammer on the 9th abdominal segment (see illustration lateral view).

The two species of Cyphoderris occurring in Montana are easily confused at first glance. There is also a third North American Grig species, the Sagebrush Grig (C. strepitans), which occurs only along the Rocky Mountain front of Wyoming and Colorado. Grigs can also be confused with the Decticids—the Shield-backed Katydids (Helfer 1971, Morris and Gwynne 1978, Vickery and Kevan 1985, and Scott 2010).

Species Range
Montana Range Range Descriptions


Range Comments
A northwest mountain species occurring from British Columbia, southward through Washington, Oregon, Idaho, western Montana, to northern California. It has been reported in four Montana counties (Vickery and Kevan 1985, and Scott 2010).

Observations in Montana Natural Heritage Program Database
Number of Observations: 3

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



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

Specimens have been found under stones and in buildings. Prefers coniferous forest areas containing Lodgepole pine (Pinus contorta), Engelmann spruce (Picea englemannii), and Mountain Hemlock (Tsuga mertensiana). The Great Grig is the only species in this genus that climbs trees to about 18 feet. Field observations indicate they usually occur in groups of 2 to 4 individuals on the same tree trunk with their heads pointed upward (Morris and Gwynne 1978, Vickery and Kevan 1985, and Scott 2010).

Food Habits
Great Grig (C. monstrosa) adults and nymphs have been found to feed on the staminate cones of Lodgepole pine (Pinus contorta) (this is before the cones reach the “loose pollen” stage). This causes this Grig species to climb high in the conifers (Morris and Gwynne 1978, Vickery and Kevan 1985, and Scott 2010).

Reproductive Characteristics
The following is taken from Morris and Gwynne (1978), Vickery and Kevan (1985), and Morris et al. (1989). When a receptive female arrives at a singing male, she mounts him so that her mouth parts are above his short forewings (the tegmina). The male ceases singing, lifts and separates the tegmina, exposing his smaller hindwings. If the female does not move away, she begins to consume her mate’s hindwings, releasing the flow of hemolymph (equivalent to blood in other organisms). While the female feeds, the male extends his telescoping abdomen with its dorso-posterior pinching organ (called the “gin trap”) and attempts to grasp and draw the female’s genitalia into contact with his genitalia. Upon making successful contact, the female continues to feed on the wings, the male’s abdomen pumps up and down releasing and transferring a spermatophore with a spermatophylax, which the female consumes after mating. The nutrients contained in the wings and spermatophylax (the “nuptial gifts”) enables the female to produce her eggs. Both male and female are ready to mate again, but the male has a problem. He may no longer possess enough nutritious hind wing material left from the first mating to attract and feed a second mate because the hind wings do not grow back. Thus, females generally prefer to mate with virgin males.

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Citation for data on this website:
Great Grig — Cyphoderris monstrosa.  Montana Field Guide.  .  Retrieved on , from