Two New Species of the Spider Family Amaurobiidae from the Ryukyu Islands, Japan

Abstract

Two new species of the family Amaurobiidae are described from the Ryukyu Islands, southwestern Japan, under the names Callobius cavernarius sp. n. (Okinoerabu Island) and Callobius shimojanai sp. n. (Okinawajima Island). Both species are closely related to each other and there are three further known species related to the new species: C. yakushimensis Okumura 2010, C. amamiensis Okumura et al., 2018 and C. breviprocessus Okumura et al., 2020. The morphological differences between these five species are discussed in detail, especially those in the structure of the male palpal organ and the female genitalia. Although this species group includes cavernicolous species, no particular adaptations to living in caves, for example degeneration of the eyes, was observed. A map showing the distribution of these species is given.