2005 年 54 巻 1 号 p. 51-63
We investigated opilionid fauna of the Oki Islands (Shimane Prefecture) in the Sea of Japan for the first time. As a result, a total of 14 species were collected from the four main islands (12, 4, 4, and 6 species from Is. Dôgo, Is. Nakanoshima, Is. Nishinoshima, and Is. Chiburi, respectively). A list of the species with some taxonomical notes is presented. Opilionid fauna of the islands may be characterized by: 1) the absence of some species which are commonly found in the San'in area of the mainland Honshu such as Gagrellula ferruginea Loman, and Nelima satoi Suzuki; 2) occurrence of some species that indicate the circum-Japan Sea distribution, such as Leiobunum rubrum Suzuki and Melanopa grandis Roewer; 3) occurrence of some species showing geographical differentiation, though there are no endemic forms at the species level; and 4) affinity to the mainland area around Mt. Daisen (Tottori Pref.) rather than mainland areas of the Shimane Prefecture in the species composition; 5) The numbers of species found on the islands generally exceed those expected from the species-area relationship in and around Japanese Islands. Leiobunum wegneri Šilhavý 1976 described from North Korea is newly synonymized with Leiobunum japonicum japonicum Müller 1914. Likewise, Metagagrella damila Šilhavý 1976 and Gagrella crassitarsi Ha et al. 2004, both originally described from Korean Peninsula, are synonymized with Melanopa grandis Roewer 1910. Two Korean species recently recorded under the names Leiobunum rotundum (Latreille 1798) and Leiobunum rupestre (Herbst 1799) by Ha et al. (2004, Korean Arachnology, 20: 53-71) from Korea are misidentifications of Leiobunum japonicum japonicum and Odiellus aspersus (Karsch 1881), respectively.
