The conifer-feeding webspinning sawfly genus Acantholyda is reviewed for Japan. Fourteen species, one of which has two subspecies, are recognized and keyed. Of these, two species and one subspecies, A. mizunoi from central Honshu (host plant : Tsuga), A. tsuyukii from central Honshu and Shikoku (host plant : Tsuga), and A. aglaia stigma from central Honshu (host plants : Picea and Abies), are described as new. This is the first Palearctic host plant record of Acantholyda from a species of Abies. Descriptions are given for the previously unknown males of A. albomaculata Shinohara, 1985 and A. iwatai Takeuchi, 1938, and A. iwatai is newly recorded from Shikoku and Kyushu. New host plant records are given for A. nipponica Yano and Sato, 1928 and A. sasakii (Yano, 1916).