Key to the Japanese species of Spilopteron 1. Hind femur with a distinct convexity ventrally; S1 with a distinct sharp projection basally (see Ito et al. 2012). Ovipositor sheath long (2.7–3.0 times as long as hind tibia) .................................... .................................................................................................................... S. mucronatus Lee, 2008 – Hind femur without a convexity ventrally; S1 without a sharp projection basally. Ovipositor sheath short to long (less than 2.6 times as long as hind tibia) .................................................................... 2 2. Postscutellum roundly convex in lateral view (Fig. 5b, d, g, j–k). Body with yellow markings or entirely reddish yellow (Fig. 5b, d); males never with a white band on antennal flagellum (Fig. 1h); body relatively large (10–17 mm) .................................................................................................... 3 – Postscutellum flat in lateral view (Fig. 5a, c, e, f, h–i). Body entirely black or with yellow markings (Fig. 5a, c); males sometimes with a white band on antennal flagellum (Fig. 1b); body relatively small (6–13 mm) ............................................................................................................................... 6 3. Body entirely reddish yellow (Fig. 5d); fore wing with only an infuscate marking apically (Fig. 4d) ..................................................................................................... S. luteum (Uchida, 1934) – Body at least with black parts (Fig. 5b, k); fore wing with one or two distinct dark markings (Fig. 4b, k) ........................................................................................................................................ 4 4. Depression between eye and antennal socket absent (Fig. 2 j–k); clypeus with three weak projections (Fig. 2 j–k). Body black with yellow markings or yellow with black markings (Fig. 5 j–k); fore wing sometimes with a black spot below the pterostigma (Fig. 4k) ................ S. tosaense (Uchida, 1934) – Depression between eye and antennal socket present (Fig. 2b, g); clypeus with two strong lateral projections (Fig. 2b, g). Body black with yellow markings (Fig. 5b, g); fore wing never with a black spot below the pterostigma (Fig. 4b, g) ............................................................................................ 5 5. Apical black marking of fore wing extending downwards (Fig. 4g); T1 slender (3.5–4.3 times as long as wide); ovipositor sheath long (2.3–2.6 times as long as hind tibia) ....................................... ........................................................................................................................ S. oblongulum sp. nov. – Apical black marking of fore wing rounded, not extending downwards (Fig. 4b); T1 broad (2.2–3.3 times as long as wide); ovipositor sheath short (1.8 times as long as hind tibia) ..................................................................................................... S. apicale (Matsumura, 1912) 6. Fore wing with only an infuscate apical portion (Fig. 4c, h) ............................................................ 7 – Fore wing with a distinct black marking apically (Fig. 4a, f, i) ....................................................... 8 7. Area superomedia of propodeum rounded (Fig. 6c); ovipositor sheath short (1.9 times as long as hind tibia) (Fig. 1c). Antennal flagellum with a white band in female and male (Fig. 1d) ........................................................................................................ S. brachyurum sp. nov. – Area superomedia of propodeum squared (Fig. 6h); ovipositor sheath long (2.0–2.3 times as long as hind tibia). Antennal flagellum with a white band in female but without it in male (Fig. 1f, j) ................................................................................................... S. pseudonigrum sp. nov. 8. Malar space long (length of malar space 1.3–1.4 times as long as basal mandibular width); apex of metasoma yellowish white (Fig. 1 a–b) ............................................................. S. albiventre sp. nov. – Malar space short (length of malar space 0.9–1.2 times as long as basal mandibular width); apex of metasoma black (Fig. 1 e–f) .............................................................................................................. 8 9. Apical black marking of fore wing rounded, not extending downwards (Fig. 1i); apical margin of clypeus turned up in lateral view. Antennal flagellum with a white band in female and male ................................................................................................... S. pyrrhonae Kusigemati, 1981 – Apical black marking of fore wing extending downwards (Fig. 1f); apical margin of clypeus flattened. Antennal flagellum with a white band in female but without it in male (Fig. 1f) .............................. ................................................................................................................................ S. nigrum sp. nov.

Published as part of Ito, Masato & Maeto, Kaoru, 2017, Revision of the genus Spilopteron Townes, 1965 (Hymenoptera: Ichneumonidae: Acaenitinae) from Japan, pp. 1-33 in European Journal of Taxonomy 356 on pages 30-31, DOI: 10.5852/ejt.2017.356, http://zenodo.org/record/3836333