Steiroxys trilineatus

The three pale longitudinal stripes on a dark background are diagnostic and immediately distinguish S. trilineatus from other Steiroxys species. S. pennatus lacks striping and has a uniformly colored pronotum. S. strepens has irregular mottling rather than clean longitudinal lines. The shieldback pronotum shape separates this genus from meadow katydids (Conocephalinae) and bush katydids (Phaneropterinae). Look for reduced wings and long antennae to confirm family-level placement in Tettigoniidae.

Medium-sized katydid, 15–25 mm in body length, with a distinctly flattened, shield-like pronotum that extends backward over the thorax and partially covers the wings (tegmina). Dorsal surface marked by three conspicuous pale yellow or cream-colored longitudinal stripes: one centered along the midline and one on each lateral margin of the pronotum and abdomen. Ground color ranges from dark brown to blackish, creating strong contrast with the pale striping. Antennae extremely long, filiform, and often exceeding body length. Hind femora enlarged for jumping. Wings reduced to small tegmina in both sexes; hindwings absent or vestigial. Cerci slender and tapering.

Grassland and sagebrush steppe ecosystems; specifically associated with bunchgrasses (Poa, Festuca, Agropyron), sagebrush (Artemisia tridentata), and rabbitbrush (Chrysothamnus). Occupies the ground layer and lower vegetation strata, sheltering under rocks, in grass tussocks, and within leaf litter during daytime. Elevation range approximately 1,200–2,500 m. Requires relatively open, dry conditions with sparse shrub cover; avoids dense forest and riparian areas.

Western North America: documented from southeastern Washington, eastern Oregon, southern Idaho, Nevada, Utah, western Wyoming, and northern Colorado. Core range centers on the Great Basin and northern Rocky Mountain foothills. Distribution appears continuous through suitable habitat patches but may be locally fragmented due to agricultural conversion and invasive annual grasses.

Adults present July through September, with peak activity in August. Nymphs overwinter and mature through spring and early summer. Males begin singing in late July. Single generation per year (univoltine).

Herbivorous; feeds on green tissues of grasses and forbs. Specific host plants documented include bluebunch wheatgrass (Pseudoroegneria spicata), Idaho fescue (Festuca idahoensis), and various Asteraceae. No evidence of carnivory or scavenging.

Egg stage: females deposit eggs in soil or at base of grass stems using sword-like ovipositor, likely in autumn. Nymph stage: overwintering occurs as mid-to-late instar nymphs; development resumes in spring with 5–6 instars total. Adult stage: sexually mature individuals present for 6–8 weeks; mating occurs following male song production. No parental care.

Males sing from concealed positions within grass tussocks or under vegetation, producing a continuous trill or series of chirps via tegminal stridulation. Song likely serves mate attraction; no evidence of aggressive acoustic interaction between males. Cryptic and sedentary during daylight hours; becomes active at dusk and night. When disturbed, jumps explosively and seeks immediate cover in vegetation or ground litter. No observed territorial behavior.

Primary consumer converting plant biomass to animal tissue; serves as prey for birds, small mammals, and invertebrate predators including spiders and robber flies. Contributes to nutrient cycling through herbivory and deposition of frass. May influence plant community composition through selective feeding on grasses, though impact likely minor given low population densities.

No direct economic importance. Occasionally encountered by hikers and field biologists in western grasslands. Not considered a pest of crops or rangeland. Vulnerable to habitat loss from agricultural conversion, fire suppression, and invasion by cheatgrass (Bromus tectorum), which alters fuel loads and vegetation structure.

• Steiroxys pennatusLacks the three pale longitudinal stripes; pronotum uniformly dark brown or black without contrasting pattern.
• Steiroxys strepensHas irregular, broken, or mottled pale markings rather than the clean, continuous longitudinal stripes of S. trilineatus.
• Aglaothorax speciesShieldback katydids with reduced wings, but pronotum more rounded posteriorly and lacking the bold tripartite striping pattern.

• Tettigoniidae
• shieldback katydid
• grassland
• sagebrush
• Great Basin
• flightless
• striped
• summer active
• herbivore
• western North America
• cryptic
• ground-dwelling
• univoltine
• stridulation

• BugGuide