Notes on immature biology of a rare skipper Caltoris bromus yanuca Fruhstorfer (Lepidoptera: Hesperiidae), with a discussion on the systematic status of Parnara ranrunna Sonan

Caltoris bromus yanuca Fruhstorfer is considered one of the rarest skippers in Taiwan and was previously believed to occur only in southern lowland part of the island. The host association and immature biology of this species are recorded for the first time. Investigation throughout the island establishes the larval host of this skipper as Phragmites vallatoria, a reed widespread in freshwater wetlands. The skipper turns out to be closely associated with its larval host and it was found nearly everywhere P. vallatoria grows. Possible reasons for the rarity of this skipper in the literature are provided, and a more reliable diagnosis of this taxon, enabling separation from a similar, sympatric skipper C. cahira austeni is presented. Moreover, the systematic status of C. ranrunna, a taxon not recorded since its original description, is clarified based on a comparison between the type of this taxon and the specimens obtained as a result of the present study.