Trachyrhachys aspera

Distinguished from sympatric Trachyrhachys kiowa by: (1) hindwing with large black band extending to apex versus mainly transparent in kiowa; (2) pronotal lateral lobe posteroventral angle right-angled versus acute and drawn down in kiowa; (3) hind femur inner face with one light transverse bar versus two in kiowa; (4) high dorsal keel on hind femur versus low keel in kiowa; (5) thin brush of hairs on lower keel versus dense brush in kiowa. Nymphs distinguished by single pale bar on inner hind femur versus two bars in kiowa, and later phenology.

Medium-sized grasshopper with brown, mottled gray and black coloration. Hindwing marked by large black band often extending to apex. Hind femur with high dorsal keel (fin) and thin brush of hairs on lower keel; inner face chiefly black with one light transverse bar. Pronotal lateral lobe with posteroventral angle approximating right angle. Nymphs short and robust with brown body, black markings, yellow or pale tan venter; hind femur inner face mainly black with one pale yellow bar in front of knee.

Shortgrass prairie dominated by blue grama grass; limited occurrence in desert prairie and western edge of mixedgrass prairie. Vegetation characterized by blue grama as dominant, subdominant grasses, forbs, small shrubs, and extensive bare ground. Requires patches of blue grama for daytime activity and bare ground or ground litter under blue grama canopies for nocturnal shelter.

Western North America from Wyoming and Nebraska south to central Mexico. Distribution spotty in northern range; widely distributed in shortgrass prairie near center of range in New Mexico. Specific records from Colorado, Wyoming, Nebraska, New Mexico, Texas (Trans-Pecos and southwest), and Mexico (Northeast and Southwest regions).

Hatching begins first week of July in north-central Colorado (elevation 5,400 ft), continuing 7–10 days; similar timing in Trans-Pecos, Texas, delayed in southwest Texas by spring rainfall patterns. Nymphal development July through mid-August (47–58 days, average 51 days). Adults present mid-August through October. Males fledge one week before females.

Feeds almost exclusively on blue grama grass (Bouteloua gracilis). Crop contents of adults: 99–100% blue grama in Colorado shortgrass prairie; 80% blue grama and 20% hairy grama (Bouteloua hirsuta) in western Texas desert prairie. Laboratory preference tests confirm strong preference for blue grama over western wheatgrass, red threeawn, downy brome, and threadleaf sedge. Consumes green leaves from tip to base, handling detached leaf sections with front tarsi.

• Bouteloua gracilis - primary hostBlue grama grass; dominant plant in habitat and nearly exclusive food source
• Bouteloua hirsuta - secondary hostHairy grama; minor component of diet in western Texas desert prairie

Univoltine. Eggs deposited in small bare areas between grama plants at depths of 1/4 to 1 1/4 inches; no pod formed, light froth coating on some eggs. Clutch size 12–18 eggs; female fecundity 1–48 eggs (average 30) in laboratory. Egg length 4.6–5.2 mm, yellow to dark brown, some two-toned. Oviposition triggered by declining photoperiod of late summer; no eggs produced under 12-hour light conditions, successful oviposition under 7-hour light/17-hour dark regime.

Diurnal activity pattern: rests on bare ground under blue grama canopies at night; emerges 2 hours after sunrise to bask for 90 minutes to 2 hours with side perpendicular to sun and hindleg lowered to expose abdomen. Thermoregulatory behavior includes stilting and climbing vegetation to shade body when ground temperatures exceed 115°F (10:40 am to 4:30 pm). Feeding occurs after sunset when temperatures moderate. Flushed flight short (3–4 ft), low (4–6 in), silent. No appetitive flights observed. Courtship brief: stridulating males approach females, jump onto back from ~1/2 inch distance. Copulation observed late morning.

Subdominant herbivore in shortgrass prairie grasshopper assemblages; chronically low densities (0.27–0.72 young adults per square yard) with stable perennial populations in favorable habitats. Contributes to cumulative forage consumption in multi-species outbreak assemblages despite never achieving dominant status. Daily adult mortality approximately 2%, allowing extended survival into late fall.

Potential rangeland pest: feeds on blue grama, a primary livestock forage. Estimated forage loss of 20 pounds dry weight per acre at density of one young adult per square yard. No documented outbreak events despite potential; populations remain subdominant even during regional grasshopper outbreaks. No records in Cooperative Economic Insect Survey damaging reports (1951–1980). Not attracted to bran bait.

• Trachyrhachys kiowaSympatric congener sharing blue grama habitat; distinguished by transparent hindwing, acute pronotal lobe angle, two pale bars on hind femur inner face, low dorsal keel, dense hair brush on lower keel, and earlier phenology (hatches ~4 weeks earlier)
• Aulocara elliottiSimilar-sized rangeland grasshopper with comparable dry weights; distinguished by different color pattern, wing morphology, and broader diet including multiple grass species

• grasshopper
• shortgrass prairie
• blue grama specialist
• band-winged
• univoltine
• late-season phenology
• subdominant
• rangeland
• North America
• thermoregulation
• photoperiod-dependent reproduction

• BugGuide
• Wikipedia
• GBIF taxonomy match
• iNaturalist taxon
• Catalogue of Life
• Grasshoppers of Colorado
• Finned Grasshopper
• Grasshoppers of Colorado
• Grasshoppers of Colorado
• Species Records and Accounts
• Kiowa Grasshopper