Montana Field Guide

The following is taken from Helfer (1971), Capinera and Sechrist (1982), Vickery and Kevan (1985), Pfadt (2002), Capinera et al. (2004), Bailey et al. (2007), and Scott (2010). The Mormon Cricket is not a true cricket, but a flightless shieldbacked katydid in the family Tettigoniidae, often referred to as “Dectids” (subfamily Tettigoniinae, tribe Decticinae), subfamily Decticinae [the shieldbacks]). This is a large-sized robust species with short wings concealed by the pronotum. In some male’s, the wings extend posteriorly, slightly beyond the hind margin of the pronotum. The hind femur is short, being no longer than twice the length of the pronotum. The body color is variable, from brown to shining black or grass green, sometimes uniform, but more commonly mottled. The female possesses an upward curved ovipositor. Antennae are longer than the body. The Mormon Cricket occurs in both solitary and gregarious forms resulting in body color variations. Solitary populations on the eastern slope of the Rocky Mountains are typically colored brown or green, whereas the more widely distributed gregarious populations are typically black.

Calling song description
The male song has been verbally described as a “shrill, whistling sound” or a “squeaking noise.” Calling males are basically unaffected by temperature regimes since they tolerate cold conditions more than other species of katydids and crickets. A male usually stops calling once he makes contact with a female (Gwynne 1984 and 2001, Bailey et al. 2007, Walker SINA website 2020).

The eggs are laid in summer and attain full development by fall when they diapause before entering winter dormancy. At high elevations embryonic development may be delayed which prolongs egg incubation an extra year. Nymphs begin hatching in spring when the soil temperatures reach 40 degrees F, survive cool spring weather and emerge at much lower temperatures than many other Orthoptera species within their habitats. Adults occur from June to September (Capinera and Sechrist 1982, Vickery and Kevan 1985, Pfadt 2002, Capinera et al. 2004, Scott 2010).

The following comes from Hebard (1928), Helfer (1971), Capinera and Sechrist (1982), Vickery and Kevan (1985), McDaniel (1987), Pfadt (2002), Capinera et al. (2004), and Scott (2010). The pronotal (thorax) length of the male is 7-<15 mm and for females, 9-15 mm. The male body length is 39-43 mm, and females are 41-49 mm, her ovipositor >19->22 mm. The male cerci are parallel and strongly curved inward with the lower branches acute and much longer than the upper branch which is blunt or slightly pointed (see illustration).

The Mormon Cricket is easily confused with any of the shieldbacked katydids (subfamily Tettigoniinae), especially its congener, the Long-legged Anabrus (A. longipes), but this species has been reported for only one northwest Montana county.

The following is taken from Cowan (1929), Gwynne (2001), and Pfadt (2002). After the eggs hatch and the first two nymphal instar stages are complete, the Mormon Crickets form small gatherings, accumulating into larger groups called bands, whereupon they begin their daily movements. Measured population densities of Mormon Crickets can range from 1 individual per square yard to over 100 per square yard, with densities growing gradually over several years reaching outbreak proportions. Once their populations have reached outbreak densities, they begin an extensive migration to the foothills, grasslands, and croplands. These marches occur only during the warm daylight hours throughout their life into the adult stage, and generally march at a rate of one-eighth to 1.25 miles per day. They only halt during rain, extreme heat (when soil surface temperatures reach =110° F), and the cooler hours of night when the band seeks “roosting shelter” beneath vegetation. In the morning, they begin emerging from their roosts when the temperature reaches about 40° F and bask in patches of sunlight, warming-up for the next daily march. The course of the march is oriented in a single, straight direction and never deviates from any obstacles, houses, barns, etc. There are observations of these marches merging into other bands, forming massive fronts more than 1 mile wide and 10 miles deep, which often result in oily, slippery roads when crushed by traffic and devastates considerable acreages of agricultural crops in their endless search for food (refer to Management below). They cease migrating 2-3 hours before sunset, bask on the ground facing west, individually or in clusters of 25-50 individuals, sitting close together. They also cluster on fence posts, utility poles and the sides of buildings. During the last three hours of daylight, Mormon Crickets also do much of their feeding before retreating to their shelters or roosts.

The Mormon Cricket inhabits a wide variety of open, scantily vegetated areas where sagebrush and forbs dominate. Large populations occur in the sagebrush-grass associations in the Great Basin and the mountain ranges of the Rocky Mountains where they occur in small resident populations in forest openings from 6500 feet to the alpine tundra at 11,000 feet (Vickery and Kevan 1985, Pfadt 2002).

The following comes from Cowan (1929), Vickery and Kevan (1985), Gwynne (2001), and Pfadt (2002). The Mormon Cricket has been observed feeding on more than 400 plant species, but it discriminates on its choice of foods, preferring succulent forbs in the wild such as milkvetches, penstemons, arrow-leaf balsamroot (Balsamorhiza sagittata), dandelion, wild mustard, tumble-mustard, and pepperweed. It also consumes shrubs associated with its habitat such as saltbush and three species of sagebrush. At certain times during its seasonal occurrence, it may restrict its diet to 2 to 4 species available in its habitat. The Mormon Cricket especially favors seeds, but grasses are low on their preferred food list, therefore, this species is not as significant an impact upon livestock forage as was once thought. They voraciously feed upon such cultivated plants as wheat, barley, alfalfa, sweetclover, truck crops and garden vegetables. The Mormon Cricket also consumes fresh manure, other wounded or dead insects, dead snakes, and any kind of dead flesh, raw or cooked. They also practice cannibalism, dining on the sick and wounded of their kind and gather at “roadkill” sites to feed upon squashed members of their migrating band.

The following is taken from Cowan (1929), Gwynne (1984), Vickery and Kevan (1985), Gwynne (2001), and Pfadt (2002). Courting and mating takes place 10 to 14 days after reaching the adult stage. The male sings from a perch in the vegetation. When an attracted female approaches, the male either drops to the ground or the female climbs the perch. When the female mounts the male, he curls into a C-shaped position beneath her, whereupon they couple. The male transfers a large white spermatophore to the female’s genitalia, consisting of two parts, a small ampulla (flask) containing two pockets of sperm and a large protein-rich bulb called the spermatophylax, after which the pair separates. While the sperm is draining into the female’s spermatheca, she eats the spermatophylax, eventually consuming the empty ampulla acquiring extra nutrients and proteins for egg production. Eggs are deposited in bare ground, often on mounds of Western Harvester ants (Pogonomyrmex occidentalis). After laying one egg, she removes her ovipositor, covers the exit hole, and moves to another location to repeat the process. Lab tests indicate that a single female lays an average of 86 eggs, but some have been observed to lay as many as 160. Egg-laying generally occurs in intervals of about 7 days and can take place at any time of day, but the greater number of eggs are usually laid in the afternoon. Mormon Crickets produce one generation per year. In colder high mountain habitats, two years may be required to produce a single generation. The nymphs pass through 7 instars before reaching the adult stage. For more detail regarding the complexity of this species’ courtship and mating systems and reversed sex roles, refer to the above references, especially those published by Darrel Gwynne.

The following comes from Cowan (1929), Claude and Parker (1947), Vickery and Kevan (1985), Gwynne (2001), and Pfadt (2002). Measured population densities of Mormon Crickets can range from 1 individual per square yard to over 100 per square yard, with densities growing gradually over several years, which eventually reach outbreak proportions. Feeding tests indicate that one cricket per square yard, from its nymphal period and 20 days of adult life, consumes an amount of vegetation equal to 38 pounds (dry weight) per acre. Due to their migratory habit, Mormon Crickets may remain at a site for no more than 3 or 4 days. Damages to agricultural and garden crops can be sizeable and can lay waste to large areas of cultivated fields. During the 1937 outbreak, crop damage in Montana amounted to $500,000 and in Wyoming amounted to $383,000. See references for more historical and more recent outbreak information.