Opeia obscura

Adults can be distinguished from similar slant-faced grasshoppers by the combination of: strongly slanted face with invisible lateral foveolae from above; single median carina on head; pronotum with parallel lateral carinae and median carina cut once behind the middle; solidly colored pronotal disk without dark stripes or triangles; and the longitudinal dark brown broken band on the tegmina. Nymphs can be separated from the superficially similar Eritettix simplex (velvetstriped grasshopper) and Psoloessa delicatula (brownspotted grasshopper) by the entirely pale tan pronotum—E. simplex has a dark velvet band along each side of the pronotum, while P. delicatula has a nearly vertical face rather than a strongly slanting one. O. obscura also hatches approximately one month earlier than these two species.

Adults are pale tan to pale green in coloration. Males are small-bodied, females medium-sized. The head has a strongly slanted face with lateral foveolae of the vertex invisible from above; the top of the head bears a single median carina. Antennae are ensiform (sword-shaped). The pronotum has nearly parallel lateral carinae and a median carina that is cut once behind the middle. The disk of the pronotum is solidly colored without dark stripes or triangles. Tegmina display a longitudinal, dark brown, broken band in the center. The hind femur has a dark stripe in the upper part of the medial area, variable in width and darkness. Hind tibia is pale tan or gray. Nymphs are pale tan with faint markings that become more evident in later instars; the median carina of the pronotum is entire in instars I-III, slightly cut in instar IV, and more so in instar V.

Inhabits grasslands of North America, particularly shortgrass and mixedgrass prairies. Thrives in habitats dominated by short grasses, especially blue grama, with patches of mid grasses used for roosting and basking. In tallgrass prairie, scattered populations may occupy upper ridges vegetated by short grasses. Typically found in areas where blue grama is abundant.

Widely distributed in the grasslands of North America, from the shortgrass prairie of Colorado to the mixedgrass prairie of Montana and Wyoming. Recorded from California, Minnesota, Montana, and parts of Mexico (Central and Northeast regions). In Wyoming, found primarily in the mixedgrass prairie of eastern Wyoming. In Arizona, adults appear as early as April. Not found in mountainous areas west of Boulder, Colorado, indicating limited dispersal into high elevations.

Late-hatching species. Eggs begin hatching in the first to last week of June in Colorado, Montana, and Wyoming; hatching period is typically two weeks but may extend to four weeks. Nymphal development requires 36 to 50 days. Adults appear from late July to early August in northern plains; as early as April in Arizona. Adults persist until October, with attrition from parasites and predators reducing numbers by late season. One generation per year.

Specialist grass feeder with strong preference for blue grama (Bouteloua gracilis). Crop contents from Colorado, Kansas, Nebraska, and North Dakota populations consisted of 85 to 100 percent blue grama. Nineteen other grass species have been recorded in crop contents in small amounts, including needle-and-thread, buffalograss, sand dropseed, little bluestem, and western wheatgrass. Trace amounts of sedges, forbs, fungi, and arthropod parts have been found. Feeds chiefly on green leaves, cutting leaves near the middle and consuming them from that point to the tip. Not observed to feed on plant litter or bran bait.

• Bouteloua gracilis - primary food plantblue grama; constitutes 85-100% of diet
• Hesperostipa comata - secondary food plantneedle-and-thread; minor component of diet
• Bouteloua dactyloides - secondary food plantbuffalograss; minor component of diet
• Sporobolus cryptandrus - secondary food plantsand dropseed; minor component of diet
• Schizachyrium scoparium - secondary food plantlittle bluestem; minor component of diet
• Pascopyrum smithii - secondary food plantwestern wheatgrass; minor component of diet

Hemimetabolous development with three stages: egg, nymph, and adult. Eggs are deposited deep in soil (5/8 to 7/8 inch depth) in pods with weak earthen walls; each pod contains 8-10 small (4-4.3 mm) pale tan eggs. Eggs overwinter in diapause and hatch in spring when soil temperatures reach approximately 50-55°F. Nymphs pass through five instars, requiring 36-50 days to reach adulthood under warm conditions. Adults have a pre-reproductive period of one to two weeks before mating. Females deposit eggs in bare ground; one observed oviposition took 100 minutes to complete, followed by 20 minutes to withdraw the abdomen and 90 seconds to brush soil over the hole. One generation annually.

Phytophilous species that spends most of each day sitting vertically, head up, on stems and leaves of grasses. Night is spent 1-2 inches above ground on grasses and sedges. Basking begins approximately one hour after sunrise by adjusting position to expose a side or back to direct sunlight; may also take diagonal positions on blue grama plants or small soil mounds. Feeding begins when ground temperature reaches 85°F and air temperature reaches 70°F. When flushed, nymphs typically jump onto another plant; adults may jump or make short evasive flights of 2-5 feet at heights of 3-6 inches. Flight is straight and silent. Under high heat (soil 110-130°F, air ≥90°F), seeks protection by climbing up to 4 inches on midgrasses, taking diagonal positions to reduce sun exposure, or resting in shade under vegetation canopy. Evening activity ends with basking in sunset rays while resting vertically on grasses.

Primary consumer in grassland ecosystems; functions as a specialist herbivore on blue grama grass. At low densities (less than 8 per square yard), may become the dominant species in grasshopper assemblages, reaching peak densities of 4 per square yard. Contributes to forage loss on western rangelands through direct consumption and occasional clipping without consumption. Serves as prey for various predators and parasites including birds, rodents, flies, beetles, and parasitoid wasps. Insecticide treatment of outbreak areas can eliminate local populations for up to four years, indicating limited recolonization ability.

Considered a minor pest of rangeland in western North America. Concentrates feeding on blue grama, an important forage grass for livestock. Has two damaging habits: ingesting green leaves and occasionally cutting and dropping them without consumption. However, populations rarely reach outbreak densities (≥25 per square yard) independently; typically adds 0.3 to 3 grasshoppers per square yard to existing outbreak densities, slightly increasing overall damage. In low-density assemblages, may become dominant but remains below economic thresholds. Not susceptible to bran bait formulations of biological control agents such as Nosema locustae, limiting management options. Light weight class among range grasshoppers reduces per-capita forage consumption compared to heavier species.

• Eritettix simplexNymphs co-occur and appear superficially similar, but E. simplex has a dark velvet band along each side of the pronotum while O. obscura is entirely pale tan; both have strongly slanting faces
• Psoloessa delicatulaNymphs co-occur and appear superficially similar, but P. delicatula has a nearly vertical face while O. obscura has a strongly slanting face; O. obscura also hatches approximately one month earlier
• Ageneotettix deorumBoth are slant-faced grasshoppers in the same subfamily and may co-occur in mixedgrass prairie; A. deorum is a major outbreak species with higher vagility and different habitat preferences

• grasshopper
• slant-faced grasshopper
• blue grama specialist
• late-hatching
• rangeland pest
• North American prairie
• Gomphocerinae

• BugGuide
• Wikipedia
• GBIF taxonomy match
• iNaturalist taxon
• NCBI Taxonomy
• Catalogue of Life
• Obscure Grasshopper
• List of Species Fact Sheets| Grasshoppers of Wyoming and the West
• Grasshopper Links
• Grasshoppers of Colorado
• Grasshoppers of Colorado
• Species Records and Accounts