Ten Japanese species of the genus Spilopteron Townes, 1965 are recognized. Five new species, S. albiventre sp. nov., S. brachyurum sp. nov., S. nigrum sp. nov., S. oblongulum sp. nov. and S. pseudonigrum sp. nov., are described from Japan. Morphological discrimination between most Japanese species is confirmed by sequence analysis of the mitochondrial COI gene, which indicates the following relationships: S. oblongulum sp. nov. + S. apicale (Matsumura, 1912), S. brachyurum sp. nov. + S. nigrum sp. nov. + S. pseudonigrum sp. nov., and S. tosaense (Uchida, 1934) + S. luteum (Uchida, 1930). A key to the Japanese species of Spilopteron is provided. This genus seems to have its center of diversity in the mid-latitude area of East Asia.
New species, parasitoid, mtCOI, taxonomy, geographical color variation, melanism, East Asia.