Army cutworm

Definition

The larval stage of the noctuid moth Euxoa auxiliaris, a migratory, soil-dwelling caterpillar that feeds aboveground on young plants at night and hides belowground by day. Larvae are polyphagous, often damaging small grains, alfalfa, and vegetable crops in outbreak years across western North America. The common name refers to the larvae's habit of moving en masse across fields when food is depleted, though they do not form true marching columns like some armyworm species (Spodoptera). Adults are robust, brownish-gray noctuids known regionally as "miller moths" due to the powdery wing scales that rub off readily.

Etymology

From "army" for the larvae's gregarious wandering behavior and "cutworm" for the habit of cutting seedlings at the soil line.

Example

In outbreak years, army cutworm larvae can defoliate winter wheat across hundreds of thousands of hectares in the Great Plains, with subsequent adult migrations producing nuisance aggregations of miller moths in urban areas along the Colorado Front Range.

Synonyms

• Euxoa auxiliaris larva
• miller moth (adult stage)

Related Terms

• Cutworm
• Armyworm
• noctuid
• Euxoa
• miller moth
• Outbreak
• economic entomology
• larval migration

Usage Notes

Distinguish from true armyworms (Spodoptera spp.), which are in a different noctuid subfamily and exhibit more cohesive group foraging. The term "army cutworm" is applied strictly to Euxoa auxiliaris; other Euxoa species may be called cutworms but not army cutworms. "Miller moth" refers specifically to the adult stage and is shared with other locally abundant noctuids that produce loose wing scales.