PROC. ENTOMOL. SOC. WASH. 104(2), 2002. pp. 479-484 THE STEM-BORING SAWFLY GENUS CEPHUS LATREILLE (HYMENOPTERA: CEPHIDAE) IN JAPAN David R. Smith and Akihiko Shinohara (DRS) Systematic Entomology Laboratory, PSI, Agricultural Research Service. U.S. Department of Agriculture, % National Museum of Natural History, Smithsonian Insti-tution, Washington, DC 20560-0168, U.S.A. (e-mail: [email protected]); (AS) Department of Zoology, National Science Museum (Natural History), 3-23-1 Hyakunin-cho, Shinjuku-ku, Tokyo 169-0073, Japan (e-mail: [email protected]) Abstract. — Two species of CepJnis occur in Japan, C hyalinatus Konow from Hokkaido and C. brachycercus Thomson, newly recorded from Japan, from Honshu. Clarification of past records of Cephus in Japan are presented. A key, descriptions, and illustrations of the abdomen are given for both species. Key Words: stem-borers, Cephidae, Cephus, Japan Cephas is primarily a Eurasian genus of 20 to 25 species, all of which are associated with grasses. Gussakovskij (1935) keyed and discussed 23 Palearctic species, Benson (1946) estimated 25 world species, and Mu-che (1981) keyed and discussed 31 world species. Two species occur in North Amer-ica, but one, Cephus pygmaeus (L.) is an introduction, and the other, Cephus cinctus Norton, is still open to question as to whether it is native or an early introduction from eastern Asia. Larvae bore and feed in the stems of grasses and can be especially destructive in cultivated grain crops such as wheat. Takeuchi (1938) recorded four species of Cephus from northeastern Asia, but two of them, C. nigripennis Takeuchi and C sach-alinensis Takeuchi, are now placed in Cal-ameuta Konow (Benson 1946). Of the other two, one, Cephus hyalinatus Konow, is known from eastern Asia including Japan (Hokkaido), and the other, C. camtschat-calis Enslin, from Kamtchatka and Sakha-lin. Takeuchi (1938) corrected his previous record of Cephus canitschatcalis Enslin from Hokkaido (Takeuchi 1936) to Cephus hyalinatus. Takeuchi later recorded C. cani-tschatcalis from Kunashiri Island, but this is corrected to C. hyalinatus in this paper. Togashi (1997, 1998) gave collection re-cords of Cephus hyalinatus from Akan, Hokkaido, and Niigata Prefecture, Honshu, respectively, but the latter was corrected to Stenocephus oncogaster Shinohara by Shi-nohara (1999). Specimens of this genus are not com-monly collected in Japan, and only a few from Hokkaido and Honshu are represented in collections. Based on about 35 specimens available, we record two species from Ja-pan, Cephus hyalinatus from Hokkaido and Cephus brachycercus Thomson from Hon-shu. The former is widespread in eastern Asia, and the latter is widespread in Eurasia and is reported here for the first time from Japan. Based on the specimens available, there are rather constant color differences between those collected in Honshu and those from Hokkaido. Thus, at present we prefer to treat them as separate species, and we attempt to clarify past records from Ja-pan.