Abstract
The genus Lewisister Bickhardt, 1912 was previously only known to contain a single species, L. excellens Bickhardt, 1912, and had only been recorded from Southeast Asia. In this study, a new species found in Taiwan, L. masumotoi sp. nov., is described and the male genitalia are illustrated. Additional morphological characters are presented for L. excellens Bickhardt, 1912 and an illustration of its male genitalia is provided. The pairwise genetic distance of COI sequences of Lewisister are also provided to support the delimitation of both species. Both species are distributed in Taiwan, and the distribution records from Taiwan are discussed.