Two tibicinine species, Cicadetta pellosoma (Uhler, 1861) and Cicadetta isshikii (Kato, 1926), were recently collected from a new locality, Mt. Gwangdeoksan, where the two species are sympatric. It was observed for the first time that pellosoma or isshikii perched on high places of tall trees in the forest. From this habitat, several individuals of the intermediate forms between the typical pellosoma and the typical isshikii were collected. As the degrees of the development of green markings in these intermediate forms show a gradual variation from the typical pellosoma to the typical isshikii, it is highly probable that Cicadetta pellosoma and Cicadetta isshikii should be synonymous.