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Abstract
Nine species of Hygrobates (Acari: Parasitengona: Hygrobatidae) from Hokkaido, Japan are described or redescribed from newly collected material and historical specimens. Treated herein are eight species in the subgenus Hygrobates, including one new species, H. bibi sp. nov., as well as H. calliger Piersig, Citation1896; H. foreli (Lebert, Citation1874); H. japonicus Uchida, Citation1931; H. longipalpis (Hermann, Citation1804); H. longiporus Thor, Citation1898; H. nigromaculatus Lebert, Citation1879; and H. sokolowi Thor, Citation1927. Also treated is H. ezoensis Uchida, Citation1934 in the subgenus Rivobates. A lectotype and paralectotype are designated for H. japonicus Uchida, Citation1931. Hygrobates (s. str.) heteropalpis Imamura, Citation1954 is synonymized with H. calliger Piersig, Citation1896. The name H. ezoensis Uchida, Citation1934 is resurrected from synonymy with H. diversiporus Sokolow, Citation1927. Six species previously known from Hokkaido were collected in the study: H. foreli, H. japonicus, H. longipalpis, H. longiporus, H. diversiporus, and H. ezoensis. New records for both Hokkaido and Japan include H. nigromaculatus and H. sokolowi. A species previously recorded from Hokkaido, H. taniguchii Imamura, Citation1954, was not found in this study. Three new characters are proposed as useful for the taxonomy of the genus Hygrobates: the ratio of the distance between the P‐4 ventral setae to P‐4 length, the ratio of the length of the longest terminal seta on IV‐L‐5 to the length of IV‐L‐5, and the nature of the outer border of the genital plates.
Acknowledgements
We are deeply grateful to the following colleagues for their generous help, and wish to extend our heartfelt thanks: Professor Haruo Katakura and Associate Professor Shin Tochinai, Hokkaido University, provided valuable assistance in numerous ways. Ms Tomiko Ito, Hokkaido Fisheries Experimental Station; Dr Kazuyuki Onimaru, Bihoro Museum; Dr Yoshikazu Takashima, Marine Biological Research Institute of Japan Co., Ltd; Mr Kazunori Saito, Asahikawa University; Ms Chiharu Sato, Graduate School of Education, Hirosaki University; and Mr Ko Tomikawa and Mr Shinpei Hiruta, Graduate School of Science, Hokkaido University, helped with collecting specimens or provided specimens. Dr Jun‐ichi Aoki, Kanagawa Prefectural Museum of Natural History, shared his knowledge of acarology and helped with collecting. Dr Gen Takaku, Hokkaido University of Education, suggested useful techniques and provided other information. Dr Hiroshi Abe, Nihon University, helped obtain references and shared his knowledge of water mites. Dr Reinhard Gerecke, Tübingen, donated some European Hygrobates samples and likewise provided useful information on water mites. Dr Hiroshi Morino and Dr Yoshiaki Kikuchi, Ibaraki University, kindly loaned Imamura's collection. This work was supported by a fellowship to N.M. from the Northern Advancement Center for Science and Technology, and by the COE Program on Neo‐Science of Natural History, Graduate School of Science, Hokkaido University (M.H.D.).