Chrysozephyrus rarasanus (Matsumura), a species formerly considered as an endemic of Taiwan, is now found from continental China and described as a new subspecies: C. rarasanus occiduus n. subsp. The new subspecies has less intensive metallic green scaling on wings compared to the nominotypical subspecies. Larva of the new subspecies feeds on Quercus sessilifolia (Fagaceae), the same host utilized by the nominotypical subspecies. Due to the fact the plant is widely distributed, it is likely that C. rarasanus is much more widespread in distribution than currently recognized.
