Review of the spider genus Simon, 1894 in Western Japan and Central Ryukyu with the description of three new species (Araneae, Linyphiidae).

Three new species of the genus Simon, 1894 are recorded and described from Western Japan, all based on both sexes. Of these, two species are endemic to the Ryukyu Archipelago: Ballarin & Eguchi, from Amami-Ōshima Island, and Ballarin & Eguchi, from Okinawa Honto and Kume-jima Islands. These species represent the first record of the genus for the Central Ryukyus and belong to a newly defined species group. Another new species, Ballarin & Eguchi, is recorded from eastern Kyushu in mainland Japan and belongs to the group. The phylogenetic positions of the new species are discussed based on morphological and molecular data. New records, remarks, and photos of genitalia of other poorly known species from surrounding areas (Taiwan, Kyushu, Shikoku, and western Honshu) are provided to facilitate future identifications.