At present, only one Stertinius species, S. kumadai Logunov, Ikeda & Ono 1997, is known from Japan. In this paper, a new species, S. ryukyuensis sp. nov., is described and compared with S. kumadai, which
is redescribed. Despite similarities in general appearance, the two species can be separated based on the morphology of retrolateral tibial apophysis and male cheliceral teeth, as well as the position of large spermathecal
chamber.
