Eupnigodes megacephala
McNeill, 1897
Big-headed grasshopper
Eupnigodes megacephala is a -sized widely distributed across western North America. Formerly classified as Aulocara elliotti, this is notable for its disproportionately large, rounded and bright hind . It inhabits shortgrass prairies, desert grasslands, and occasionally montane areas up to 8,500 feet elevation. The species is economically significant as a rangeland pest, capable of reaching that severely reduce forage for livestock and promote soil erosion.
Pronunciation
How to pronounce Eupnigodes megacephala: /juːpnɪˈɡoʊdiːz ˌmɛɡəˈsɛfələ/
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Identification
Distinguished from similar by the combination of large rounded , bright hind , and spotted . May be confused with -winged grasshoppers due to general appearance, but lacks the colored hind typical of that group. Distinguished from Aulocara femoratum (formerly congeneric) by pronotal pattern and female : E. megacephala females lack deep clefts on the margin of the eighth abdominal . identifiable by triangular foveolae visible in view, flattened , and drab gray-tan coloration with fuscous markings.
Habitat
Shortgrass prairies, desert grasslands, and mixed-grass prairies with sparse vegetation. Also recorded in coniferous woodlands at elevations up to 8,500 feet. Prefers areas with bare ground for basking and .
Distribution
Western North America from southern Canada (Prairie Provinces) through the western United States to central Mexico. Ranges east to extreme western Iowa and Minnesota. Present throughout the Rocky Mountain region including Colorado, Wyoming, Montana, and Arizona.
Seasonality
active from June to September. emerge mid-spring (late May to June), completing development in 36-42 days. One annually.
Diet
Feeds primarily on green leaves of grasses and sedges. Documented include grama, western wheatgrass, needle-and-thread, thread-leaf sedge, and needleleaf sedge. Readily consumes crested wheatgrass. Also feeds on ground litter including cut grass (green or dry), seeds, bran, and even dead . content analyses indicate mixed diet averaging 2.2 per individual, though one species typically predominates.
Life Cycle
Overwinters as in pods laid at shallow depth (average 3/8 inch). Eggs undergo partial embryonic development (to stage 19, ~50%) before entering winter . Hatching triggered by soil temperatures rising to 50°F and above, requiring approximately 450 (base 50°F) to complete development. Nymphal stage lasts 36-42 days; males typically have 4 , females 5 instars. live 15-72 days depending on conditions; unprotected individuals average ~20 days. Females oviposit 12-20 days after maturation, depositing 7-9 eggs per pod. averages 76 eggs per female on western wheatgrass, 116 on wheat leaves, with maximum recorded 161 eggs.
Behavior
ground-dwelling . Basks perpendicular to sun rays in early morning and late afternoon, lowering hindleg to expose . Normal activity (pottering, feeding, mating, ) begins around 70°F air temperature and 95°F soil temperature. Escapes high ground temperatures (>120°F) by stilting (raising body on legs) or moving to of shrubs. Evasive straight, silent, low (4-12 inches), and short (2-7 feet). Capable of flights of 1-7 miles. Ovipositing females sweep soil over exit hole using hind as brushes.
Ecological Role
in many western grassland . At (20-40 per square yard), significantly reduces and can alter vegetation structure. Creates ground litter through grass-cutting , which supports . Serves as for birds, rodents, , , and other . subject to high (54% density reduction fall to spring).
Human Relevance
Major economic pest of rangeland grasses. reduce livestock forage and promote wind/water erosion by removing vegetation cover. Field cage studies indicate one individual per square yard reduces grass forage by 20 pounds dry weight per acre annually. Subject to control programs using carbaryl and biological agents including . Preserved specimens found on Glacier, Montana, indicating historical mass events.
Similar Taxa
- Aulocara femoratumFormerly congeneric; distinguished by female eighth (deep clefts present in A. femoratum, absent in E. megacephala) and subtle color pattern differences
- Band-winged grasshoppers (subfamily Oedipodinae)Similar general appearance and preference; distinguished by E. megacephala's lack of brightly colored hind and presence of large rounded
- Cordillacris occipitalisOverlapping range and ; distinguished by long and different pronotal shape