Spodoptera praefica, the western yellow-striped armyworm, is a moth of the family Noctuidae found from British Columbia to California, east to Utah, and north to Alberta. The wingspan is 35–40 mm. Adults are on wing from March to April and from August to September. The larvae feed on the leaves of various herbaceous plants including agricultural crops such as alfalfa, potato, rice, sugar beet, and sweet potato.