Complicated symptoms including antifeedance, protruding of the intistine, dark-ening of the body wall, malformation of the throax emerging of adult organs ap-peared to the larvae of diamondback moth after the larvae were treatecd with thechloroform extract of Ajuga nipponensis. Results in histological and ultrastructuralstudies showed that the larvae treated by the extract caused notable changes tothe mid-and hind-intestine cells,the epidermis cells,silk gland, the wingbuds, Malpighian and fat body.