Oedaleonotus enigma

Adults distinguished from other Oedaleonotus species by tegmina equal to or longer than pronotum (other seven species have tegmina shorter than pronotum). The white/cream anterior pronotal band is distinctive. Wing dimorphism present: short-winged forms have nonfunctional hindwings, long-winged forms have functional flight wings. Nymphs identifiable by cream-colored dorsal stripe extending from head through pronotum to abdomen, and broken fuscous chevrons on hind femur. Six nymphal instars rather than typical five.

Sagebrush-grass and semiarid rangeland associations of the western United States. Favors abandoned farmland, Conservation Reserve Program (CRP) land, and foothills of California coastal and Sierra Nevada ranges. Native host plants include springparsley, balsamroot, big sagebrush, and rabbitbrush. Thrives in areas with introduced weeds such as redstem filaree, flixweed, and downy brome.

Western North America: California, Nevada, Idaho, and surrounding states. Present in sagebrush-grass communities and semiarid rangelands.

Early hatching species. Eggs overwinter in advanced embryonic stage and hatch in early spring, beginning as early as April in California, Nevada, and Idaho, continuing for a month or longer. Hatching typically occurs in morning when air temperatures are 45-90°F and soil temperatures 76-98°F. Adults appear in late spring to early summer; first adults observed 22 May in north-central Nevada in 1954. Reproduction occurs in fall, triggered by decreasing day length and coinciding with fall rains.

Primarily forb and shrub feeder, with some grass consumption. Native hosts: springparsley, balsamroot, big sagebrush, rabbitbrush. Favors introduced weeds: redstem filaree, tumble mustard, draba mustard, pepperweed, downy brome. Heavy lichen feeder. Big sagebrush becomes important host when annual weeds dry. Will feed on ground litter and dead grasshoppers under drought conditions. Observed to feed on seven forb species, four shrubs, two grasses, one sedge, and one lichen. Does not substantially feed on Russianthistle (Chenopodiaceae) despite using it for roosting.

• springparsley - foodnative host
• balsamroot - foodnative host
• big sagebrush - foodimportant summer host when weeds dry
• rabbitbrush - foodnative host
• redstem filaree - foodintroduced weed, favored food
• tumble mustard - foodintroduced weed, favored food
• draba mustard - foodintroduced weed
• pepperweed - foodintroduced weed
• downy brome - foodintroduced weed, favored food
• lichen - foodheavy feeding observed
• Russianthistle - roostingused for shelter, not substantially eaten

Overwintering eggs in advanced embryonic stage (stage 23, post-blastokinesis) hatch early spring. Diapause breaks during winter; warming spring temperatures complete embryonic development. Six nymphal instars (vs. typical five), with nymphal period lasting 42-50 days due to cool spring temperatures. Adults reproduce in fall; eggs begin development upon laying, reach advanced stage by fall, then enter winter diapause. Females oviposit in bare ground adjacent to shrub/weed bases, under low forbs, or around rocks. Pods placed horizontally 1/8-1/4 inch below soil surface. Nymphs emerge from side of pod rather than through end.

Diurnal with bimodal activity pattern. Spends night roosting head-up on vegetation (primarily Russianthistle) or on ground. Basks in morning by turning side perpendicular to sun and lowering hindleg to expose abdomen; second basking period in late afternoon. Feeding periods in morning (starting ~8:30 a.m.) and late afternoon when temperatures moderate. Avoids high ground temperatures (>110°F) by stilting (raising on legs) or climbing vegetation to rest in shade at 4-7 inch heights. Evasive flight of long-winged adults straight, silent, 4-8 feet distance at 4-10 inch heights; brachypterous adults jump 2-8 feet. Slow dispersal of nymphs and adults occurs almost daily; concentrated band migration of 20-30 per square yard during outbreaks. Macropterous adults disperse from deteriorating habitats.

Herbivore in sagebrush-grass ecosystems. At low densities, may provide benefit by preferentially feeding on weeds, reducing competition with forage plants. Serves as prey for digger wasps (Tachysphex spp.) and parasitoid flies (Neorhynchocephalus sackenii). Population crashes during drought or from fungal disease and parasitism can affect food web dynamics.

Major rangeland pest causing severe forage injury at high densities (>20/sq yard), particularly damaging to young grasses and legumes in reseeded rangeland. Nymphs and adults migrate from rangeland into alfalfa, cotton, grains, and vegetables causing serious crop damage. Subject to integrated pest management programs. No quantitative damage assessment studies completed. Potential biological control target through parasitoid conservation.

• Melanoplus sanguinipesSimilar spur-throated grasshopper in same habitats; distinguished by different nymphal color patterns, five instars vs. six, and different adult morphological characters
• Phoetaliotes nebrascensisLarge-headed grasshopper, next species in subfamily; distinguished by very large head relative to body, slanted face, and primarily grass-feeding habit vs. forb/shrub feeding of O. enigma
• Other Oedaleonotus speciesSeven other species in genus, mainly California-distributed, distinguished by tegmina shorter than pronotum and usually narrow, widely separated

• grasshopper
• pest
• rangeland
• western North America
• wing dimorphism
• early hatching
• spur-throated
• Melanoplinae

• BugGuide
• GBIF taxonomy match
• iNaturalist taxon
• Catalogue of Life
• Valley Grasshopper
• List of Species Fact Sheets| Grasshoppers of Wyoming and the West
• Grasshoppers of Colorado
• Devastating Grasshopper
• Largeheaded Grasshopper
• Field Guide