Bathyplectes anurus (Thomson) (Hymenoptera: Ichneumonidae), a larval parasitoid of the alfalfa weevil Hypera postica (Gyllenhal) (Coleoptera: Curculionidae), was introduced to Japan from the U.S., for biological control of the weevil. The parasitoid had been released at Saeki city (Oita Pref.), Okagaki town (Fukuoka Pref.). and Miyazaki city (Miyazaki Pref.), every spring for three or four consecutive years. A detection survey was conducted in the spring following the last year of release. In Saeki city and Okagaki town. the incidence of parasitism by B. anurus was confirmed to be within 3 km of the release point. However. rates of parasitism did not exceed 2 % in both locations. The number of recovered cocoons decreased with distance from the release point. The parasitoid was not recovered in Miyazaki city. Hypera postica (Curculionidae) : Host Bathyplectes anurus (Ichneumonidae) : Parasite Animals and man; Control; Biological control; Parasites diseases and disorders; Parasites; Insect parasites; Hosts; Insect hosts; Zoogeography; Dispersal; Means of dispersal; Land zones; Palaearctic region; Eurasia; Asia Bathyplectes anurus; Control of; Hypera postica (Coleoptera); Coleopteran hosts; Parasite introduction programme effectiveness; control relationships; Hypera postica; Introduction; Introduction programme effectiveness; Japan; Kyushu, Miyazaki, Okagaki & Saeki Hypera postica; Control by; Bathyplectes anurus (Hymenoptera); Hymenopteran parasites; Parasite introduction programme effectiveness; control relationships; Bathyplectes anurus; Japan; Kyushu, Miyazaki, Okagaki & Saeki none