Bigheaded grasshopper (Aulocara elliotti) is a common and economically important species in western United States rangelands, often found in large numbers alongside the Migratory Grasshopper (Melanoplus sanguinipes). [1] It has been reported as a rangeland pest over a long period of time [2] and is among the most damaging species. [3]
Aulocara elliotti (Thomas, 1870). For full nomenclature, see this taxon's page on Orthoptera Species File
Identification
The big-headed grasshopper is most commonly found in grayish-brown colors with dark markings and a distinctive light "X" on the pronotum.[4][5] Adults are medium-sized and have relatively large heads with slightly slanted faces and spotted forewings. On the hind femur, there are two black bars on the upper part of the medial area, extending onto the upper marginal and inner medial area, with the knee appearing black. The hind tibia typically displays a medium blue hue.
Nymphs have several distinct features. Their heads are characterized by triangular depressions on the sides, while the antennae are thin and flattened, and the face slopes moderately.[4] Nymphs also have the light "X" marking on the pronotum. Moving to the hind leg, two dark bars mark the upper section, with several dark spots present on the lower part, while the hind tibia has a blue hue with three dark rings.
The big-headed grasshopper is predominantly found throughout the western grasslands of North America, from Southern Canada to central Mexico. It can be found in British Columbia, Alberta, Manitoba, Minnesota, Iowa, Kansas, Oklahoma, Texas, Western Nebraska, Western North Dakota, Arizona, New Mexico, Washington, Oregon, Los Angeles, and California.[6] Substancial populations develop in the desert, mixedgrass, shortgrass, and bunchgrass prairies.[4]
Biology
The big-headed grasshopper typically hatches during mid-spring, spanning a period of three to four weeks.[5] It generally matures into adulthood within 36 to 42 days after hatching. They deposit their eggs in firm, smooth foam egg pods positioned just beneath the soil surface, typically near the bases of grasses in open areas. It lays eggs in pod within the upper 2 cm of soil in late summer or early fall and hatch the following spring.[6] Females appear to prefer bare areas on the south side of grass clump in crested wheatgrass fields.[1]
Life cycle parameters
Phase
Developmental time
Eggs
Hopper
Adult
Laying-fledging
Adult maturation
Total
Habitat and Ecology
Aulocara elliotti is a grass feeder and prefers crested and western wheatgrass and blue grama. This species does not feed on forbs by choice and avoids sagebrush. [7][8][5][9] It consumes large quantities of cheatgrass in the spring and switches to other foods as the cheatgrass dries. Crested wheatgrass fields tend to have more bare ground between bunches which A. elliotti prefers for oviposition sites. [10]
This species can reach adult densities exceeding 50 individuals per square yard.[5] Populations tend to increase gradually over several years before experiencing sudden tripling or quadrupling in a single year. Frequently dominating outbreaks, high populations of A. elliotti have been documented to persist for over five years.[5]
Land-Use Change
Pest status
The big-headed grasshopper is on of the top dozen species monitored by USDA APHIS because of its impact on rangelands.
↑ 1.01.1 Fisher JR (1992) Location of Egg Pods of Aulocara elliotti (Orthoptera: Acrididae) in a Field of Crested Wheatgrass in Montana. Journal of the Kansas Entomological Society 65: 416–420.
↑ Cooley RA (1904) Grasshoppers. Montana Agricultural Experimental Station Bulletin. 51:232-242.
↑ Mulkern GB, Pruess KP, Knutson H, Hagen AF, Campbell JB, Lambley JD (1969) Food habits and preferences of grassland grasshoppers of the north central Great Plains. North Dakota Agricultural Experimental Station Bulletin No. 481. 32 p
↑ 5.05.15.25.35.45.5 Schell SP, Latchininsky AV, Shambaugh BA (2005) Rangeland Grasshopper Management. 2nd Edition B-1161. Laramie, WY: University of Wyoming Cooperative Extension Service and Department of Renewable Resources. 76 p.
↑ 6.06.1 Pfadt RE (1949) Food-plants, distribution, and abundance of the big-headed grasshopper, Aulocara elliotti (Thos.). Journal of Kansas Entomological Society 22: 69-74.
↑ Mulkern GB, Toczek DR, Brusven MA (1964) Biology and ecology of North Dakota grasshoppers. II. Food habits and preferences of grasshoppers associated with the sandhill prairie. North Dakota Agricultural Experimental Station Research. Report 11.
↑ Pfadt RE, Lockwood JA, Foppe TM (1988) Diets of three common grasshoppers (Orthoptera: Acrididae) inhabiting desert grassland. The Canadian Entomologist. 120: 415-424.
↑ Fielding DJ and Brusven MA (1992) Food and Habitat Preferences of Melanoplus sanguinipes and Aulocara elliotti (Orthoptera: Acrididae) on Disturbed Rangeland in Southern Idaho. Journal of Economic Entomology, 85(3), 783–788. https://doi.org/10.1093/jee/85.3.783
↑ Kemp WP and Sanchez NE (1987) Differences in post-diapause thermal requirements for eggs of two rangeland grasshoppers. The Canadian Entomologist 119: 653-661.
