Oedaleonotus

Adults of Oedaleonotus enigma, the most thoroughly documented species, are large, colorful spur-throated grasshoppers. The anterior edge of the pronotum has a narrow, conspicuously white to cream-colored band. The medial area of the hind femur is marked with fuscous chevrons separated by light tan lines, with orange coloration at the proximal end of the inner medial area and lower marginal area. Hind tibiae are blue. The male cercus is broad basally with apex abruptly narrowed and fingerlike. Seven species in the genus possess tegmina shorter than the pronotum, which are usually narrow and widely separated; O. enigma is distinguished by having tegmina ranging from short to long, with long-winged individuals having functional flight wings. Nymphs are identifiable by a fuscous band down the middle of the vertex and occiput divided by a narrow cream-colored line, a longitudinal cream-colored fusiform band down the middle of the pronotal disk, and fuscous chevrons on the medial area of the hind femur that are broken in the middle at the proximal half.

Species of Oedaleonotus inhabit semiarid rangelands, including sagebrush-grass associations and foothill environments. Oedaleonotus enigma specifically inhabits abandoned farmland, Conservation Reserve Program land, and foothills of the California coastal and Sierra Nevada ranges. Native host plants include springparsley, balsamroot, big sagebrush, and rabbitbrush. The increase in introduced weeds such as redstem filaree, flixweed, and downy brome has created favorable conditions for population outbreaks.

The genus Oedaleonotus is distributed in western North America. Distribution records indicate presence in California, Nevada, and Utah. Oedaleonotus enigma has a continental distribution centered in the western states, with populations documented in Idaho, Nevada, and California. Seven species are distributed mainly in California.

Oedaleonotus enigma hatches early in spring, with hatching beginning in early April in California, Nevada, and Idaho and continuing for a month or longer. Hatching usually occurs in the morning when air temperatures are between 45° and 90°F. Nymphal development requires approximately 42 to 50 days, with adults appearing from late May through summer. The species has six nymphal instars rather than the typical five, contributing to its relatively long nymphal period. Reproduction occurs in late summer and fall, with eggs entering diapause in an advanced embryonic stage and hatching the following spring.

Oedaleonotus enigma is primarily a forb and shrub feeder that also feeds to some extent on grasses. Documented food plants include springparsley, balsamroot, big sagebrush, rabbitbrush, redstem filaree, tumble mustard, draba mustard, pepperweed, downy brome, and lichen. Russianthistle is used for roosting but not consumed. Under drought conditions, individuals resort to feeding on ground litter and dead or dying grasshoppers. Laboratory observations confirm feeding on leaf edges of forbs such as miniature rose and spearmint.

• springparsley - food plant
• balsamroot - food plant
• big sagebrush - food plantimportant host plant in summer when annual weeds have dried
• rabbitbrush - food plant
• redstem filaree - food plantintroduced weed
• tumble mustard - food plantintroduced weed
• draba mustard - food plantintroduced weed
• pepperweed - food plantintroduced weed
• downy brome - food plantintroduced weed
• lichen - food plant
• Russianthistle - roosting siteused for shelter but not consumed

Oedaleonotus enigma overwinters as eggs in an advanced embryonic stage (stage 23, after blastokinesis). Eggs enter diapause in fall; diapause breaks during winter, and warming spring temperatures enable completion of embryonic development. Hatching occurs early in spring. Nymphs develop through six instars, becoming adults in 42 to 50 days. Adults may be short-winged (brachypterous) or long-winged (macropterous); wing dimorphism is influenced by temperature during development, with cooler temperatures producing higher proportions of long-winged adults. Females oviposit in bare ground adjacent to shrub bases, under low-growing forbs, and around rocks. Pods are placed horizontally 3-6 mm below the soil surface, slightly curved, 12-16 mm long and 3-5 mm in diameter, containing 16-22 eggs each. Eggs are olive tan and 4.8-5.2 mm long. Nymphs emerge from the side of the pod rather than through the end.

Oedaleonotus enigma exhibits basking behavior in morning and late afternoon, turning perpendicular to sun rays and lowering the hindleg to expose the abdomen. During hot midday periods, individuals climb vegetation to 10-18 cm heights and rest vertically head-up in shade. Daily activity includes two foraging periods: morning (beginning around 8:30 a.m.) and late afternoon. Feeding occurs on leaf edges, with individuals either standing on the ground or holding onto plants with midlegs and hindlegs while using front tarsi to direct leaves to mouthparts. Slow dispersal occurs almost daily; during outbreaks, nymphs migrate in concentrated bands following draws with greener vegetation. Long-winged adults can fly from deteriorating habitats to more favorable areas. Evasive flights are straight, silent, and short (1.2-2.4 m distance, 10-25 cm height). Brachypterous adults evade threats by jumping 0.6-2.4 m. Males attend ovipositing females.

At low densities, Oedaleonotus enigma may provide benefits by preferentially feeding on weeds, thereby reducing competition with valuable forage plants. At high densities, it becomes a destructive pest, consuming rangeland forage and migrating into crops. The species serves as prey for digger wasps (Tachysphex spp.) and is parasitized by the tangle-veined fly Neorhynchocephalus sackenii. Population outbreaks may be terminated by drought or predation.

Oedaleonotus enigma is a significant agricultural pest. High densities on rangeland cause severe injury to forage plants and are particularly damaging to young grasses and legumes in newly reseeded rangeland. Outbreak populations migrate into alfalfa, cotton, grains, and vegetables, causing serious damage. The species has high reproductive capacity, with adult densities reaching 20 or more per square yard. No quantitative study of damage has been made. The species was involved in major outbreaks in California rangelands during 1955-1961, contributing to infestations covering millions of acres alongside Melanoplus devastator and Camnula pellucida.

• MelanoplusBoth are spur-throated grasshoppers in subfamily Melanoplinae. Oedaleonotus can be distinguished by the white to cream-colored anterior pronotal band and specific hind femur color patterns; male cercus shape also differs.
• Phoetaliotes nebrascensisBoth are large Melanoplinae grasshoppers with some wing dimorphism. Phoetaliotes has a very large head relative to body size and feeds almost exclusively on grasses, whereas Oedaleonotus has a more proportional head and is primarily a forb feeder.
• Other Oedaleonotus speciesSeven other Oedaleonotus species have tegmina shorter than the pronotum, usually narrow and widely separated, whereas O. enigma has variable tegmina length from short to long.

• spur-throated grasshopper
• Melanoplinae
• pest species
• rangeland
• wing dimorphism
• migratory

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