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

Abstract

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