Two new species and a new genus of ray spiders (Araneae, Theridiosomatidae) from the Ryukyu Islands, southwest Japan, with notes on their natural history.

This paper provides descriptions of two new theridiosomatid species, and , from the Ryukyu Islands, southwest Japan, with photographs and illustrations of both sexes. is a troglophilic genus composed of two species, (Iriomote Island, Japan) and (Zhu, Zhang & Chen, 2001), (southern China). Miller, Griswold & Yin, 2009, which recently joined the Japanese fauna, was morphologically reexamined based on specimens from the Ryukyus, and taxonomic features of males were reassessed. A distributional map of theridiosomatid spiders in the Ryukyus is also provided, including Suzuki, Serita & Hiramatsu, 2020, and Suzuki, Serita & Hiramatsu, 2020 with their habitat types, web morphology, and web-building behavior in detail.