Fall armyworm

Definition

A highly polyphagous moth species (Spodoptera frugiperda, family Noctuidae) whose larvae are destructive agricultural pests, characterized by gregarious, dispersive 'army-like' feeding behavior and rapid long-distance migration. Native to the tropical Americas, it has spread globally as an invasive species, attacking maize, rice, sorghum, cotton, and numerous other crops. The species exhibits two partially reproductively isolated host strains (corn-strain and rice-strain) that provide a model for sympatric speciation, and larvae display facultative cannibalism despite fitness costs.

Etymology

From 'fall' (autumn generation in North America) + 'armyworm' (larval habit of marching en masse to new food sources); Latin specific epithet frugiperda ('fruit-destroying').

Example

Fall armyworm larvae typically hatch in dense aggregations and, upon depleting local vegetation, disperse in coordinated fronts that can devastate consecutive maize fields within days.

Synonyms

• Spodoptera frugiperda

Related Terms

• Armyworm
• Spodoptera
• Noctuidae
• polyphagy
• Sympatric speciation
• host race
• Cannibalism
• migratory pest
• stem borer
• Integrated Pest Management

Usage Notes

Distinguished from true armyworm (Mythimna unipuncta, formerly Pseudaletia) and African armyworm (Spodoptera exempta) by geographic range, host preferences, and strain structure. The corn-strain and rice-strain are morphologically cryptic but differ in pheromone blend, host plant use, and mitochondrial haplotype; they are not yet formally recognized as separate species despite reproductive isolation. In invasion biology literature, 'FAW' is common shorthand.