Agrotis orthogonia

Distinguished from other Agrotis cutworms by its subterranean feeding habit and association with dry, sandy soils of western North America. Larvae feed specifically on crown stems below the soil surface rather than cutting plants at or above the surface. The pale western cutworm can be separated from the black cutworm (Agrotis ipsilon) and other congeneric species by geographic range (western drylands vs. broader distribution) and habitat preference. Adults may require dissection or molecular methods for definitive identification from related species.

Dry, semi-desert areas of western North America. Prefers loose, sandy, dry, or dusty soils. Associated with agricultural fields, particularly wheat, and weedy or grassy areas that serve as oviposition sites. The species thrives in arid and semi-arid environments with well-drained soils.

Western North America from southern Canada (Alberta, Saskatchewan, Manitoba) southward to California, ranging eastward nearly to the eastern edge of the Great Plains. Present in the Canadian prairies and the western United States.

Adults emerge and are active in late summer and fall (August–October), when mating and oviposition occur. Eggs hatch primarily in late winter or early spring, with larval development proceeding through spring. Larvae pupate in soil in early summer, with the pre-pupal stage over-summering until August pupation.

Larvae feed subterraneously on stems of wheat and other small grains, specifically targeting the crown region just below the soil surface. They may also feed on other grass hosts. Adults likely feed on nectar or other liquid sources, though specific adult diet is not documented.

• Triticum aestivum - larval food plantprimary agricultural host
• small grains - larval food plantgeneral host category including barley, oats, rye
• grasses - larval food plantwild grass hosts for oviposition and early feeding

Females deposit up to 300 eggs per individual in cultivated soil during late summer and fall. Some eggs may hatch in fall, but most overwinter and hatch in late winter or early spring. Larvae develop through spring, feeding subterraneously on plant stems. Mature larvae burrow into soil to form pre-pupal cells in early summer, over-summering in this stage. Pupation occurs in August, with adults emerging shortly thereafter. There is one generation per year.

Larvae are nocturnal feeders that remain underground during daylight hours. They exhibit typical cutworm behavior of curling into a C-shape when disturbed. The subterranean feeding habit distinguishes this species from surface-feeding cutworms. Adults are nocturnal and attracted to light. Outbreak populations can develop rapidly under favorable dry conditions, with larvae capable of destroying fields in days during severe infestations.

As a primary consumer, larvae transfer energy from plants to higher trophic levels. The species serves as prey for generalist predators including birds, ground beetles, and parasitoids. Population outbreaks can significantly alter plant community structure in agricultural systems. The species is considered a pest in agroecosystems but likely functions as a natural herbivore in native grassland ecosystems.

Major agricultural pest of wheat and small grains in western North America. Economic damage occurs when larvae sever stems below the soil surface, causing wilting, stand thinning, and plant death. Outbreaks are favored by dry spring conditions. Management relies on cultural practices (weed control, seedbed preparation) and insecticide applications. Action thresholds suggest treatment at 1 larva per square foot when yield potential is good, or 2 per square foot when yield potential is low. Insecticide seed treatments and at-planting applications are used preventively.

• Agrotis ipsilonBlack cutworm; distinguished by surface-feeding behavior, broader geographic distribution, and darker larval coloration
• Euxoa messoriaDarksided cutworm; differs in larval color pattern and surface-feeding habits
• Agrotis exclamationisHeart and dart moth; European species with different larval behavior and geographic range

• cutworm
• Noctuidae
• agricultural pest
• wheat pest
• subterranean feeder
• western North America
• dryland agriculture
• monvoltine
• soil-dwelling larva

• BugGuide
• GBIF taxonomy match
• iNaturalist taxon
• NCBI Taxonomy
• Catalogue of Life
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