Abstract: 【Aim】 The moth Orvasca subnotata Walker (Lepidopetra: Lymantriidae) is a severe defoliator of Dalbergia odorifera T. Chen found in manmade forests, and its biological characteristics and the determination of its larval instars are the important basis for the pest forecast and control in the forest. 【Methods】 The morphological characteristics, the habit of each developmental stage and the life history of O. subnotata were investigated though regular field sampling. Through regular forest sampling and morphological characterization, three indicators of larval instar features including the head capsule width, prothoracic verruca width and body length were recorded and analyzed. 【Results】 We described the biological characteristics of O. subnotata with an emphasis on its developmental features. Our results showed that as the larvae grow, the prothorax gradually darkens, and the abdominal back line and poison gland color gradually deepen. Statistical analysis of the body measurements showed that both the head capsule width and prothoracic verruca width could be used as indicators of developmental stages with head capsule width being superior to prothoracic verruca width, and the prothoracic verruca width and head capsule width were significantly correlated (y=0.994 x-0.114, R=0.999). The body length distribution fits the Dyar’s law. However, due to the overlap distribution among developmental stages, body length is not a reliable indicator of larval instar determination. 【Conclusion】 The results will help the identification of O. subnotata in the field and provide some crucial information for developing control and prevention strategies.

Key words: Orvasca subnotata, biological characteristics, larval instar, head capsule width, prothoracic verruca width