Mesitius nigripilosus Ashmead, 1895:539, ♀. Holotype ♀, Tepic, 1894 (leg. Messrs, Eisen & Vaslit); Barbosa & Azevedo, 2014Barbosa, D.N. & C.O. Azevedo 2014. Revision of the Neotropical Laelius (Hymenoptera: Bethylidae) with notes on some Nearctic species. Zoologia 31 (3):285-311.:294, Lectotype ♂, examined (USNM, #14060). - Dalla Torre, 1898Dalla Torre, C.G. 1898. Catalogus Hymenopterorum hucusque descriptorum systematicus et synonymicus, V. Chalcididae et Proctotrupidae. Sumptibus Guilelmi Engelmann, VII + 598. (distribution); Barbosa & Azevedo, 2014Barbosa, D.N. & C.O. Azevedo 2014. Revision of the Neotropical Laelius (Hymenoptera: Bethylidae) with notes on some Nearctic species. Zoologia 31 (3):285-311.:307 ( listed as synonym of Laelius huachucae (Evans, 1965)). - As Epyris nigripilosus: - Evans, 1964Evans, H.E. 1964. A synopsis of the american Bethylidae (Hymenoptera, Aculeata). Bulletin of the Museum of Comparative Zoology 132 (1):1-222. (distribution). - As Rhabdepyris nigripilosus: - 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 2. Apocrita (Aculeata). Smithsonian Institution Press, Washington D.C. 1199-2209. (distribution); Murgas & González, 2006Santos Murgas, A. & P.E. González D. 2006. Dostrobicón de especies de la subfamilia Epyrinae (Hymenoptera: Bethylidae) en Panamá. Tecnociencia 8 (2):37-50. (distribution).
Laelius billi Barbosa & Azevedo, 2014:294 Replacement name for Mesitius nigripilosus Ashmead, 1895 by Barbosa & Azevedo, 2014Barbosa, D.N. & C.O. Azevedo 2014. Revision of the Neotropical Laelius (Hymenoptera: Bethylidae) with notes on some Nearctic species. Zoologia 31 (3):285-311.:294 (nec Laelius nigripilosus Ashmead, 1893 - et nec Rhabdepyris nigropilosus Evans, 1966). - Barbosa & Azevedo, 2014Barbosa, D.N. & C.O. Azevedo 2014. Revision of the Neotropical Laelius (Hymenoptera: Bethylidae) with notes on some Nearctic species. Zoologia 31 (3):285-311. (distribution).