Genus Tersilochus Holmgren, 1859

Tersilochus is a predominantly Holarctic species (the Nearctic fauna is virtually undescribed) comprising about 75 species, of them 67 species are Palaearctic (Yu et al. 2016), and beyond the Holarctic region the genus is known in Africa (Khalaim 2019) and tropical Asia (Khalaim 2011). Nine species were reviewed from Russian Far East and Japan (Khalaim 2012), and ten species were found to occur in South Korea (Khalaim et al. 2014)

Ten species of Tersilochus, including a new species described in this paper, occur in Japan.

Most host records of the genus are from the beetle families Chrysomelidae, Curculionidae and Nitidulidae (Coleoptera), but two species were reared from leaf mining Eriocraniidae (Lepidoptera) (Jordan 1998) and some species of the subgenus Pectinolochus probably parasitise tenthredinid sawflies ( Hymenoptera: Tenthredinidae) (Yu et al. 2016).