Obscure grasshopper (Opeia obscura)
| Opeia obscura Obscure grasshopper | |
|---|---|
 | |
| Distribution | |
| Arizona, California, Colorado, Idaho, Kansas, Montana, Nebraska, Nevada, New Mexico, North Dakota, Oklahoma, South Dakota, Texas, Wyoming, Alberta, Saskatchewan, Chihahua, Durango, Guanajuato, Mexico (State), Nuevo Leon, Puebla, San Luis Potosi, Tamaulipas | |
| Taxonomy | |
| Family: | Acrididae |
| Subfamily: | Gomphocerinae |
| Genus: | Opeia |
| Additional resources | |
| Full taxonomy at OSF | |
The obscure grasshopper (Opeia obscura) inhabits areas across North American grasslands and is a periodic rangeland pest. The coloration of these grasshoppers, combined with their small, narrow bodies and tendency to remain stationary, allows them to camouflage against their environments. This trait has earned them the name “obscure” grasshopper.
Nomenclature
Opeia obscura (Thomas, 1872). For full nomenclature, see this taxon's page on Orthoptera Species File
Identification
The obscure grasshopper 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.[1] 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 obscure 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 obscure grasshopper varies in color—brown, tan, green, or yellow—with a plain green or brown back and dark streaks. It has a slanted face, sword-shaped antennae, a narrow body, and wings that usually reach the end of the abdomen. Distinct dark stripes run along its sides, wings, and back legs, and females have a brown-and-white wing stripe. Nymphs are pale tan or cream with faint markings that darken as they grow, eventually showing the same features as adults.
Viewed from above, it appears slightly bug-eyed due to its narrow head and small body size. A distinctive ridge along the top of the head helps confirm its identification.[1]
Nymphs of the velvet-striped grasshopper (Erittettix simplex), the brown-spotted range grasshopper (Psoloessa delicatula), and O. obscura can appear nearly identical.[2] Some notable differences between these species are in the shape of their heads and the color patterns of their pronotal disk. P. delicatula has a near vertical face while the other two species have faces that are slanted. Additionally, the pronotal disk of O. obscura is tan without any markings, whereas E. simplex has dark velvet markings on the disk. [2] O. obscura has straight, parallel pronotal margins and narrow, sword-shaped antennae. In contrast, E. simplex typically has inward-curved pronotal sides and antennae that are slightly thickened toward the tip—though these traits may vary in southwestern populations. Both species show similar variation in color and pattern, making them hard to distinguish by appearance alone. Structural features, especially in local context, are key to accurate identification.[3]
Another key difference among these three species is that unlike the other two species, O. obscura begins to hatch nearly a month earlier. Opeia obscura is usually found as nymphs in spring and adults in summer and fall, while Encoptolophus simplex appears as nymphs in fall and adults in spring.[2][3]
Identification details
The obscure grasshopper has varied coloration.[4] Adults can be pale brown, tan, green, or yellow.[2] [5] Typically, their dorsum side is green or brown and plain, aside from some distinct fuscous streaks found on the median carina.[4]
They have a slanted face with a rounded head and sword shaped antennae.[5] Due to their narrow bodies, these grasshoppers look slightly bulging. Their wings fall just below their abdomen, though in the western states, their wings may extend past the abdomen.[6]
A wide brown stripe extends from the eyes across the lateral lobes of the pronotum to the forewing. The top of the pronotum sometimes has a narrow brown stripe. [5] There is a broken dark brown band down the length of the tegmina, running through the middle. Another dark stripe runs across the upper-middle area of the hind femur. This strip also varies in color and size. The hind tibia of adult O. obscura is pale tan or gray.[2]Females have forewings with a brown stripe bordered by a white one below. [5]
O. obscura nymphs are pale tan or cream colors. [7][2] Their markings are pale and hard to notice until they later instars. Nymphs display the same traits as adults of this species. In particular, they have strongly slanted faces, ensiform antennae, and lateral foveolae that are not visible from a top-down view. There is a dark strip on the hind femur that becomes more evident as nymphs develop. The sides of the pronotum have two lateral carinae that run parallel to each other and one median carina that runs down the middle and gets more broken as development progresses through the instars. Their hind tibia are generally pale yellow and gray.[2]
| Instar | Color | Wings | Body length | Hind femur | Antennal segment number | Description |
|---|---|---|---|---|---|---|
| Eggs | pale tan | |||||
| Egg pod | seven-eighths inch long | 4 to 4.3 mm long | eight to ten small eggs | |||
| 1 | 5.3-5.8 mm | 2.2-2.5 mm | 13 | |||
| 2 | 7.0-7.9 mm | 3.3-3.6 mm | 15-16 | |||
| 3 | 7.6-9.7 mm | 4-4.8 mm | 18-19 | |||
| 4 males | 8.2-11 mm | 4.4-6.1 mm | 21-22 | |||
| 4 females | 11.2-12.9 mm | 6.5-7 mm | 21 | |||
| 5 males | 11.5-12.2 mm | 6.5-7 mm | 22 | |||
| 5 females | 16-16.3 mm | 9 mm | 23 | |||
| Adult males | pale brown, tan, green, or yellow[2][5] | |||||
| Adult females | pale brown, tan, green, or yellow[2][5] |
Featured identification resources
All identification resources
Distribution
Abundant in the western United States extending from Mexico to the southern Canadian prairie provinces, especially abundant in shortgrass prairies from Alberta and Manitoba. [7] [5]
Biology
The obscure grasshopper is a late hatching species.[8] They produce one generation annually. Adults are found from July to October and early in the southern region. [5] Eggs may hatch early around the beginning of June to later at the end of the month. The nymphal period lasts around 36 to 50 days, requiring five instars to reach full development. Little is known about the copulation process.[2]
Habitat and ecology
O. obscura inhabits both thin and thick stand grasslands. It is strictly graminivorous but feeds on a wide variety of grasses. Although it has been reported in Colorado to feed exclusively on blue grama (Bouteloua gracilis), which made up about 99.6% of the nymphs' diet and 94.3% of the adults' diet in one study.[9] Adult O. obscura devote little time to foraging and instead focus on reproduction and locating safe, temperature-appropriate areas. [10] [7] They bask in sunlight during the morning and evening, reorienting to expose their bodies to the sun, often on blue grama or bare ground. At night, they rest on grasses 1–2 inches above the ground. When disturbed or temperatures rise, they seek new perches or shelter in vegetation or shade.[2]
These insects mostly feed in a head up direction, though may feed on needleandthread leaves in a head down position at times, eventually returning to the head-up orientation after some time of feeding.[2] The obscure grasshopper blends in easily with its surroundings, often resembling grass blades or plant debris, making it highly camouflaged.[11]
Adult obscure grasshoppers rarely fly, instead they move intermittently by walking or through short jumps.[7] When threatened, they fly a distance of three to six inches, reaching a height of two to five feet, and may land on vegetation or directly on the ground. In supportive environments, the obscure grasshopper remains within the habitats they developed in as nymphs.[2]
Land-Use Change
Pest status
The obscure grasshopper can become highly abundant and harm rangelands, especially due to their preference for feeding on blue grama grass, which also leads to the buildup of wasteful plant litter. [2][5] In mixed-grass prairies, the obscure grasshopper is typically a subdominant species, but in shortgrass prairie communities, it can become dominant. [2] If management strategies ever considered prescribed burns, fire intensity had no effect on egg mortality on O. obscura, which lays its eggs 1.6 to 2.2 cm below the soil surface.[12] It is one of the top dozen species monitored by USDA Animal and Plant Health Inspection Service (APHIS) because of its impact on rangelands.
Outbreaks
Eastern Wyoming experienced a boom in obscure grasshopper populations inhabiting mixed grass prairies during 1973 and 1974.[2]
Outbreak media coverage
No results found in the database at this time—please reach out if you have any to share!
Associated organizations
| Organization name | Acronym | Website | Type | Focus | Focus keywords | Geographic purview |
|---|---|---|---|---|---|---|
| California Department of Food and Agriculture | CDFA | https://www.cdfa.ca.gov/ | Government | Management, Governance | Management, Grasshoppers, Control | California |
| Cooperative Extension Ventura County | https://ucanr.edu/county-office/cooperative-extension-ventura-county | Government | Education, Research, Monitoring, Management | Extension | California |
Resources
References
- ↑ 1.0 1.1 1.2 1.3 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
- ↑ 2.00 2.01 2.02 2.03 2.04 2.05 2.06 2.07 2.08 2.09 2.10 2.11 2.12 2.13 2.14 2.15 2.16 Pfadt RE (1994) Obscure Grasshopper 'Opeia obscura' (Thomas). Wyoming Agricultural Experiment Station Bulletin 912. Species Fact Sheet. https://www.ars.usda.gov/ARSUserFiles/30320505/grasshopper/Extras/PDFs/Species%20Fact%20Sheets/Obscure.pdf
- ↑ 3.0 3.1 BugGuide (n.d.) Opeia obscura – Obscure grasshopper. Iowa State University. https://bugguide.net/node/view/235126
- ↑ 4.0 4.1 Somes MP (1914) The Acrididae of Minnesota. University of Minnesota Agricultural Experiment Station, Bulletin 141, 101 pp. https://babel.hathitrust.org/cgi/pt?id=coo.31924018280846&seq=20&q1=Opeia+
- ↑ 5.0 5.1 5.2 5.3 5.4 5.5 5.6 5.7 5.8 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.
- ↑ Johnson DL (2003) Slant-faced grasshoppers of the Canadian Prairies and Northern Great Plains. Arthropods of Canadian Grasslands 9: 5–16. Biological Survey of Canada, Ottawa. https://www.ars.usda.gov/ARSUserFiles/30320505/grasshopper/ID%20Tools/naturalist%20guides/sltgh.pdf
- ↑ 7.0 7.1 7.2 7.3 With KA, Crist TO (1995) Ontogenetic shifts in how grasshoppers interact with landscape structure: an analysis of movement patterns. Functional Ecology 9: 467–476. https://doi.org/10.2307/2390072
- ↑ Przybyszewski J, Capinera JL (1990) Spatial and temporal patterns of grasshopper (Orthoptera: Acrididae) phenology and abundance on a shortgrass prairie. Journal of the Kansas Entomological Society 63(3): 405–413. https://www.jstor.org/stable/25085197
- ↑ Pfadt RE, Lavigne RJ (1982) Food habits of grasshoppers inhabiting the Pawnee site. Science Monograph 42, Agricultural Experiment Station, University of Wyoming, Laramie.
- ↑ With KA (1994) Ontogenetic shifts in how grasshoppers interact with landscape structure: an analysis of movement patterns. Functional Ecology 8(4): 477–485. https://doi.org/10.2307/2390072
- ↑ Albert PM (1907) Further researches on North American Acridiidæ. Carnegie Institution of Washington Publications No. 68, 102 pp. https://babel.hathitrust.org/cgi/pt?id=mdp.39015023570537&seq=1&q1=Opeia+
- ↑ Branson DH, Vermeire LT (2013) Heat dosage and oviposition depth influence egg mortality of two common rangeland grasshopper species. Rangeland Ecology & Management 66(1): 110–113. https://www.jstor.org/stable/23355275