Western spotted-winged grasshopper (Cordillacris occipitalis)
| Cordillacris occipitalis Western spotted-winged grasshopper | |
|---|---|
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| Distribution | |
| British Columbia, Alberta, Saskatchewan, Manitoba, Washington, Oregon, California, Idaho, Nevada, Utah, Arizona, Montana, Wyoming, Colorado, New Mexico, North Dakota, South Dakota, Nebraska, Kansas, Oklahoma, Texas | |
| Taxonomy | |
| Family: | Acrididae |
| Subfamily: | Gomphocerinae |
| Genus: | Cordillacris |
| Additional resources | |
| Full taxonomy at OSF | |
The western spotted-winged grasshopper (Cordillacris occipitalis) is a common rangeland pest in western North America, particularly when it occurs in mixed species assemblages.
Nomenclature
Cordillacris occipitalis (Thomas, 1873). For full nomenclature, see this taxon's page on Orthoptera Species File
Identification
Cordillacris occipitalis is a species of slant-faced grasshopper in the family Acrididae. Slant-faced grasshoppers are recognized by their angled facial profile and typically slender, streamlined bodies with forward-tipped, pointed heads. Most slant-faced grasshoppers in North America belong to the subfamily Gomphocerinae, commonly known as “stridulating slant-faced grasshoppers” or “tooth-legged grasshoppers,” named for the row of pegs on the inner hind legs of males used to produce sound by rubbing against the wing edges. A smaller group with similar facial structure—the Acridinae, or “silent slant-faced grasshoppers”—lacks these pegs and does not produce sound. These silent forms are found in some parts of the United States but are absent from western Canadian grasslands.
The western spotted-winged grasshopper belongs to Gomphocerinae. Members of this subfamily can be readily distinguished from other grasshopper groups: they lack the prosternal spine found in Melanoplinae and the large, colorful, lobed hind wings typical of Oedipodinae.[1] They also differ behaviorally and morphologically from Acridinae.
A few specialized anatomical terms are useful for identifying grasshoppers in this subfamily. Grasshoppers have four wings, with the leathery, protective front pair known as the tegmina. Just behind the head lies the pronotum, a saddle-shaped structure forming the upper part (notum) of the prothorax, the front segment of the thorax. Along the center of the pronotum runs the median carina, a raised ridge, which may be intersected by sulci. At the tip of the head, a central dent called the fastigium may be seen, flanked by lateral foveolae, shallow pits bordered by small ridges. These features, often visible with a hand lens, are key to distinguishing between closely related species within the subfamily.[1]
The western spotted-winged grasshopper is a medium-sized insect that blends easily into its surroundings thanks to its dull colors and small size. It’s usually brown to reddish-brown, but can also appear tan, gray, or yellowish-brown, often with subtle white markings. Look for a dark stripe running from behind the eyes across the pronotum and down to the wings. Its wings are long and usually reach the tip of the abdomen, with dark spots arranged in a line and a thin white stripe at the base. The back legs are striped with white and brown, and the hind tibiae are pale orange. The head is slanted with a rounded top, and the antennae are narrow and sword-like. Nymphs look similar but are smaller and striped with dark brown and tan patterns.
Identification details
Due to their dull coloration, small body and population size, C. occipitalis do not stand out within their habitats and may be overlooked.[2][3] Western spotted-winged grasshoppers are medium-sized[4], with males being smaller than females.[5] They range from a brown to a reddish brown color, and they are marked with white.[6] Adults may also appear to be a dull, yellowish brown color[7], or tan and gray.[4]
C. occipitalis have slanted faces, marked with a dark streak that runs from behind the eyes across the pronotum and down to the base of the forewing.[5][2]. The vertex on their heads are rounded.[7] Median carina found on the pronotum remains distinct despite being close to the pronotum surface.[4] It is divided by a cut located just behind the middle of the median carina. The lower portion of the cut median carina is emphasized by white coloring.[4]
The base of the forewings are marked with a thin white stripe and row of dark spots[5][2], while the hind wings are clear.[6][7] This species has long wings that, at the most, reach slightly past the abdomen.[4] The lower half of the lateral pronotum is white[6], and the margin at the dorsal posterior region is rounded.[7] Pronotum is constricted in the middle and the lateral carinae are obsolete.[8] These grasshoppers have ensiform antennae[4] and slightly white, opaque, tegmina that are marked with dark spots arranged in a row in the middle.[6] The common name forC. occipitalis, western spotted-winged grasshopper, stems from their characteristic wing coloration.[4]
In males these spots also appear around the edge of the wings.[6] These insects have pale orange hind tibiae[5], hind femora that are marked with a brown stripe on the outer area, and hind legs that are marked with a white streak located over the base.[7]
C. occipitalis nymphs are generally brown, tan, and gray.[5] There are two distinct stripes, dark brown in color, that extends from behind the eyes, across the pronotum, down to the bottom of the abdomen.[5] A wide stripe, colored tan and speckled with brown spots, is located on the dorsal side of the body.[4] As found on adults, the pronotum contains a low and notable median carina. They have strongly slanted heads [5] with slender antennae [7] and pointed at the tip, resembling a sword.[5] Nymphal hind femora are brown in the upper-middle region, shifting to a light gray at the lower-middle areas.[4]
| Instar | Color[4] | Wings | Body length[4] | Hind femur[4] | Antennal segment number[4] | Description[4] |
|---|---|---|---|---|---|---|
| Eggs | 4.4 - 5.6 mm | |||||
| Egg pod | White[7]; pale yellow[4] | 3/8th inch in length
1/8th inch in diameter |
Contains 3 eggs[7] located at the bottom half of the pod.[4] | |||
| 1 | 5.2-6.0 mm | 3.2-3.4 mm | 13 | Lasts approx. 5.5 days for males and females | ||
| 2 | 8.2-8.8 mm | 4.5-4.8 mm | 17 | Lasts approx. 6 days for males and females | ||
| 3 | 9.3-10 mm | 4.9-5.9 mm | 19-20 | For females specifically: lasts approx. 7 days | ||
| 4 | 9.7-13.1 mm | 5.7-8.0 mm | 21-22 | Lasts approx. 7[9] to 11 days[4]
For females specifically: may last approx. 8 days | ||
| 5 | 12.7-16 mm | 7.9-9.8 mm | 22-24 | Lasts approx. 7[9] to 11 days[4]
For females specifically: may last approx. 9 days | ||
| Adult males | 16.5-18.5 mm | 10-10.4 mm | 24-25 | Develop faster than females[5] | ||
| Adult females | 21-23.5 mm | 12-12.8 mm | 24-25 |
Featured identification resources
All identification resources
Distribution
This species is found across south-central Canada and the western United States, ranging eastward to Manitoba and North Dakota in the north, and extending south to central Oklahoma and western Texas.[2][10] Although it is rarely found in the Canadian prairies, with occurrences remaining low at less than one individual per 10,000 grasshoppers.[6]
Biology
Males court females through stridulation, femur-tipping, and by rhythmically raising and lowering their antennae to signal readiness to mate.[8] These behaviors can also signal aggression toward rival males. Females may respond to unwanted advances by raising their hind femora to kick males away or by hopping up to 1.5 feet to avoid copulation.[8][11] After mating, eggs require time to develop within the female before oviposition.[12] Females seek bare ground surrounded by preferred food plants for egg-laying, depositing eggs either on the surface or within the soil.[5][4]
Hatching begins in spring[8][10] and lasts around 4 weeks[12] with peak hatching generally around May 15 to June 1.[5] C. occipitals are part of the early hatching group.[12] Adults appear in June through September. [2]
This species overwinters in the egg stage.[7] While developing, eggs continue growth until they reach 50% development and enter diapause, before resuming and completing development in spring.[12] Nymphs complete five instars to mature into adults, developing rapidly through the first three stages, then taking seven days to complete the fourth and fifth instars each.[9] The process of maturation requires around 36 to 41 days, with immature adults taking an extra week or two of development before they can be observed within habitats.[12]
The total nymphal period takes around 22.5 days of development.[4] Female individuals reach sexual maturity around 40 days post hatching.[5] Two weeks post maturation of both males and females mated pairs begin to appear.[4]
Western spotted-winged grasshoppers rarely migrate in bands, but may disperse when food becomes scarce.[5] Their long wings enable strong flight, and when threatened, they fly straight and silently with the wind.[12][4] Evasive flights are low (2–4 inches) and short (2–4 feet).[4]
Habitat and ecology
Western spotted-winged grasshoppers are found in various grassland types including shortgrass[10], mixedgrass [13], and bunchgrass prairies. [4]
Preferred habitats include sandy or loamy soils. [13] Dry gravelly hills, eroded areas, river valleys, and arid environments with sparse, dry vegetation are also commonly occupied. [6][7][3] In such habitats, the species can become locally abundant. [2] It rarely inhabits areas with heavy soils, and when present in such conditions, populations tend to remain at low densities. [4] Individuals remain within the areas they hatched as nymphs in[12], spending most of their time on the ground.[11]
Diet-wise, this grasshopper is graminivorous, preferring green leaves and showing little selectivity in food sources. [7][12][4] It favors slightly wilted blue grama and needleandthread, as well as significantly wilted western wheatgrass. [7] Known host plants include blue grama, needleandthread, western wheatgrass, sand dropseed, downy brome, threadleaf sedge, and needleleaf sedge, with additional records of sandreed grass, threeawn dropseed, and sand dropseed. [4][7] These grasses and sedges are commonly available in its habitats. [5][13] C. occipitalis rarely feeds on forbs, plant litter, or arthropods, and is generally unlikely to consume bran poison bait. [5][4]
Due to the consumption of new leaf growth prior to the 3.5 new leaf stage, C. occipitalis are able to greatly damage their habits.[12] Adulthood coincides with the 3.5 new leaf stage for two days.[9] Western spotted-winged grasshoppers consume vegetation by climbing atop glades of grass, orienting themselves so their heads are positioned downwards, and chewing through the leaf. This method of consumption can result in excess leaf parts falling and creating litter.[12] The created litter from fallen portions of leaves by these grasshoppers can be consumed by other grasshoppers or is left as litter.[4] Though it is rare, these individuals may feed on vegetation from the ground, using their front tarsi to fully consume the plant portion.[12] However, these grasshoppers will consume apple cores from the ground in a horizontal position.[4]
The western spotted-winged grasshopper can be found on the ground or among vegetation, opting to rest either on the vegetation or on the ground during the night.[12] Nymphs sleep 2 to 7 inches off the ground on top of grass leaves.[4] Basking behavior is exhibited twice a day, occurring before sunset and after sunrise.[12] To regulate body temperatures once soil temperatures reaches 120 F, these grasshoppers climb on small shrubs about 2 to 8 inches above ground. They find shade and orient their heads upwards.[12] Spotted winged grasshoppers commonly utilize the shade from fringed sagebrush and spreading wild buckwheat plants to cool down.[4]
Land-Use Change
Pest status
Outbreaks
C. occipitalis is rarely dominant in grasshopper assemblages[13] although it is still one of the top dozen species monitored by USDA Animal and Plant Health Inspection Service (APHIS) because of its impact on rangelands. Within mixed grass prairies, their populations can remain at low densities for five years or longer. Whereas, populations inhabiting their preferred sandy loam soils have the potential to reach outbreak densities over time.[4][5]
Low densities consist of populations at around 0.2 to 0.5 individuals per square yard.[12] Densities can peak at around 40 individuals per square yard, causing substantial damage to grasses and sedges.[5] Each year, C. occipitalis populations generally experience a twofold increase, then escalate more dramatically—expanding by two to four times the following year.[12]
During outbreaks in Wyoming, this species commonly composes less than half of the grasshopper population.[5] During a 1974 grasshopper outbreak in Wyoming, C. occipitalis appeared as the dominant species reaching a density of 20 individuals per square yard. Spotted winged grasshopper outbreaks are influenced by the density of adults that survive into the late summer.[4]
Outbreak media coverage
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Associated organizations
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Resources
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References
- ↑ 1.0 1.1 Johnson DL (n.d.) Slant-faced grasshoppers of the Canadian Prairies and Northern Great Plains. Environmental Health, Agriculture and Agri‑Food Canada Research Centre, Lethbridge, AB & University of Lethbridge, Lethbridge, AB, Canada. https://hopperwiki.org/images/5/5b/Slant-faced_grasshoppers_of_the_Canadian_Prairies_and_Northern_Great_Plains.pdf
- ↑ 2.0 2.1 2.2 2.3 2.4 2.5 Capinera JL, Scott RD, Walker TJ (2005) Field guide to grasshoppers, katydids, and crickets of the United States. Cornell University Press, Ithaca, New York, 280 pp.
- ↑ 3.0 3.1 Hebard, M. (1925). The Orthoptera of South Dakota. Proceedings of the Academy of Natural Sciences of Philadelphia, 77, 33–155. http://www.jstor.org/stable/4063970
- ↑ 4.00 4.01 4.02 4.03 4.04 4.05 4.06 4.07 4.08 4.09 4.10 4.11 4.12 4.13 4.14 4.15 4.16 4.17 4.18 4.19 4.20 4.21 4.22 4.23 4.24 4.25 4.26 4.27 4.28 4.29 4.30 4.31 4.32 4.33 Pfadt RE (1994) Spottedwinged Grasshopper 'Cordillacris occipitalis' (Thomas). Wyoming Agricultural Experiment Station Bulletin 912. Species Fact Sheet. https://www.ars.usda.gov/ARSUserFiles/30320505/grasshopper/Extras/PDFs/Species%20Fact%20Sheets/Spottedw.pdf
- ↑ 5.00 5.01 5.02 5.03 5.04 5.05 5.06 5.07 5.08 5.09 5.10 5.11 5.12 5.13 5.14 5.15 5.16 5.17 Schell SP, Latchininsky AV, Shambaugh BA (n.d.) Common Wyoming pest grasshoppers. University of Wyoming Cooperative Extension Service Bulletin B-1161, Laramie, 76 pp. https://www.wyoextension.org/agpubs/pubs/B1161.pdf
- ↑ 6.0 6.1 6.2 6.3 6.4 6.5 6.6 Johnson DL (2003) Slant-faced grasshoppers of the Canadian Prairies and Northern Great Plains. Arthropods of Canadian Grasslands 9: 1–24. https://www.ars.usda.gov/ARSUserFiles/30320505/grasshopper/ID%20Tools/naturalist%20guides/sltgh.pdf
- ↑ 7.00 7.01 7.02 7.03 7.04 7.05 7.06 7.07 7.08 7.09 7.10 7.11 7.12 Capinera JL, Sechrist TS (1982) Grasshoppers (Acrididae) of Colorado: identification, biology and management. Colorado State University Agricultural Experiment Station, Fort Collins, Bulletin No. 584S, 161 pp. https://archives.mountainscholar.org/digital/collection/p17393coll54/id/34541
- ↑ 8.0 8.1 8.2 8.3 Vickery VR, Kevan DK (1985) The grasshoppers, crickets and related insects of Canada and adjacent regions: Ulonata: Dermaptera, Cheleutoptera, Notoptera, Dictuoptera, Grylloptera, and Orthoptera. Insects and Arachnids of Canada, Part 14. Agriculture Canada, Ottawa, 918 pp. https://publications.gc.ca/collections/collection_2016/aac-aafc/agrhist/A42-42-1985-14-eng.pdf
- ↑ 9.0 9.1 9.2 9.3 Manske LL (n.d.) Pestiferous rangeland grasshopper forage use in the Northern Plains. North Dakota State University, Dickinson Research Extension Center, Report DREC 14-1081, 28 pp. https://www.ag.ndsu.edu/dickinsonrec/archive/annual-reports-1/2013-annual-report/grassland13g.pdf
- ↑ 10.0 10.1 10.2 Richman DB, Lightfoot DC, Sutherland CA, Ferguson DJ (1993) Manual of the grasshoppers of New Mexico – Orthoptera: Acrididae and Romaleidae. Handbook 7. New Mexico State University Cooperative Extension Service, Las Cruces, NM, 112 pp. https://nmsu.contentdm.oclc.org/digital/collection/AgCircs/id/63174
- ↑ 11.0 11.1 Otte D (1970) A comparative study of communicative behavior in grasshoppers. Miscellaneous Publications of the Museum of Zoology, University of Michigan 141: 1–168. https://hdl.handle.net/2027.42/56385
- ↑ 12.00 12.01 12.02 12.03 12.04 12.05 12.06 12.07 12.08 12.09 12.10 12.11 12.12 12.13 12.14 12.15 Manske LL, Schneider SA (2014) Proactive Management of Pestiferous Rangeland Grasshopper Habitat of the Northern Plains. North Dakota State University, Dickinson Research Extension Center, Bulletin DREC 14-4021 https://www.ndsu.edu/agriculture/sites/default/files/2022-10/grassland14h.pdf
- ↑ 13.0 13.1 13.2 13.3 Brust ML, Hoback WW, Wright RJ (2008) The Grasshoppers (Orthoptera: Acrididae and Romaleidae) of Nebraska. University of Nebraska–Lincoln Extension, Lincoln, Nebraska, 129 pp. https://www.ars.usda.gov/ARSUserFiles/30320505/grasshopper/ID%20Tools/eb3.pdf