Metopius basalis Cresson, 1879:xxvii, ♀.Florida; Davis, 1897Davis, G.C. 1897. A review of the Ichneumonid subfamily Tryphoninae. Transactions of the American Entomological Society 24 (3/4):193-348.:199, Type (Amer. Ent. Soc.); Townes & Townes, 1959Townes, H.K. & M. Townes 1959. Ichneumon-flies of America north of Mexico: 1. Subfamily Metopiinae. Bulletin of the United States National Museum 216 (1):1-318.:105, Type ♀ (Philadelphia). - Davis, 1897Davis, G.C. 1897. A review of the Ichneumonid subfamily Tryphoninae. Transactions of the American Entomological Society 24 (3/4):193-348. (distribution); Dalla Torre, 1901-1902Dalla Torre, C.G. 1901-1902. Catalogus Hymenopterorum hucusque descriptorum systematicus et synonymicus. — Volumen III: Trigonalidae, Megalyridae, Stephanidae, Ichneumonidae, Agriotypidae, Evaniidae, Pelecinidae. Pars II. Breitkopf & Härtel, Leipzig. VIII + 1141. (distribution). - As Metopius basalis basalis: - Krombein et al., 1979Krombein, K.V., P.D. Hurd, D.R. Smith & B.D. Burks 1979. Catalog of Hymenoptera in America North of Mexico. Volume 1. Symphyta and Apocrita (Parasitica). Smithsonian Institution Press, Washington D.C. 1-1198. (distribution).
Metopius medianus Morley, 1912:78, ♂. Holotype ♂, Georgia (British Museum, leg. probably taken by Edward Doubleday); Townes & Townes, 1959Townes, H.K. & M. Townes 1959. Ichneumon-flies of America north of Mexico: 1. Subfamily Metopiinae. Bulletin of the United States National Museum 216 (1):1-318.:105, Type ♂ (London). Synonymized with Metopius basalis basalis Cresson, 1879 by Townes & Townes, 1959Townes, H.K. & M. Townes 1959. Ichneumon-flies of America north of Mexico: 1. Subfamily Metopiinae. Bulletin of the United States National Museum 216 (1):1-318.:105. - Krombein et al., 1979Krombein, K.V., P.D. Hurd, D.R. Smith & B.D. Burks 1979. Catalog of Hymenoptera in America North of Mexico. Volume 1. Symphyta and Apocrita (Parasitica). Smithsonian Institution Press, Washington D.C. 1-1198.:553 ( listed as synonym of Metopius basalis basalis Cresson, 1879).