Stigmus smithii Ashmead, 1900:223, ♀. Holotype ♀, St. Vincent; Finnamore, 1995Finnamore, A.T. 1995. Revision of the world genera of the subtribe Stigmina (Hymenoptera:Apoidea: Sphecidae: Pemphredoninae), Part 1. Journal of Hymenoptera Research 4:204-284.:238, Holotype ♂ (not ♀) (BMNH, Hym 21.886); Finnamore, 2002Finnamore, A.T. 2002. Revision of the world genera of tribe Stigmini (Hymenoptera: Apoidea:Crabronidae: Pemphredoninae), Part 2. Species of Incastigmus Finnamore. Journal of Hymenoptera Research 11 (1):12-71.:64, Holotype ♂, Ashmead incorrectly described this specimen as a female (BMNH, Hym. 21.886). Synonymized with Incastigmus thoracicus (Ashmead, 1900) by Finnamore, 1995Finnamore, A.T. 1995. Revision of the world genera of the subtribe Stigmina (Hymenoptera:Apoidea: Sphecidae: Pemphredoninae), Part 1. Journal of Hymenoptera Research 4:204-284.:238. - Ashmead, 1900Ashmead, W.H. 1900. Report upon the aculeate Hymenoptera of the islands of St. Vincent and Grenada, with additions to the parasitic Hymenoptera and a list of the described Hymenoptera of the West Indies. Transactions of the Entomological Society of London pt. II:207-367. (distribution); Amarante, 2002Amarante, S.T.P. 2002. A synonymic catalog of the neotropical Crabronidae and Sphecidae (Hymenoptera: Apoidea). Arquivos de Zoologia (São Paulo) 37:1-139.:53 ( listed as synonym of Incastigmus thoracicus (Ashmead, 1900)); Finnamore, 2002Finnamore, A.T. 2002. Revision of the world genera of tribe Stigmini (Hymenoptera: Apoidea:Crabronidae: Pemphredoninae), Part 2. Species of Incastigmus Finnamore. Journal of Hymenoptera Research 11 (1):12-71.:64 ( listed as synonym of Incastigmus thoracicus (Ashmead, 1900)).
Stigmus thoracicus Ashmead, 1900:223, ♀. 4 ♀♀, St. Vincent and Grenada; Finnamore, 1995Finnamore, A.T. 1995. Revision of the world genera of the subtribe Stigmina (Hymenoptera:Apoidea: Sphecidae: Pemphredoninae), Part 1. Journal of Hymenoptera Research 4:204-284.:238, Holotype ♀ (BMNH, Hym 21.885); Finnamore, 2002Finnamore, A.T. 2002. Revision of the world genera of tribe Stigmini (Hymenoptera: Apoidea:Crabronidae: Pemphredoninae), Part 2. Species of Incastigmus Finnamore. Journal of Hymenoptera Research 11 (1):12-71.:64, Holotype ♀, examined (BMNH, Hym. 21.885). - Ashmead, 1900Ashmead, W.H. 1900. Report upon the aculeate Hymenoptera of the islands of St. Vincent and Grenada, with additions to the parasitic Hymenoptera and a list of the described Hymenoptera of the West Indies. Transactions of the Entomological Society of London pt. II:207-367. (distribution); Evans, 1972Evans, H.E. 1972. Bredin-Archbold-Smithsonian Biological Survey of Dominica: Aculeate Wasps (Hymenoptera: Scolioidea, Vespoidea, Pompiloidea, Sphecoidea). Smithsonian Contributions to Zoology 115:1-19. (distribution). - As Incastigmus thoracicus: - Finnamore, 1995Finnamore, A.T. 1995. Revision of the world genera of the subtribe Stigmina (Hymenoptera:Apoidea: Sphecidae: Pemphredoninae), Part 1. Journal of Hymenoptera Research 4:204-284. (distribution); Amarante, 2002Amarante, S.T.P. 2002. A synonymic catalog of the neotropical Crabronidae and Sphecidae (Hymenoptera: Apoidea). Arquivos de Zoologia (São Paulo) 37:1-139. (distribution); Finnamore, 2002Finnamore, A.T. 2002. Revision of the world genera of tribe Stigmini (Hymenoptera: Apoidea:Crabronidae: Pemphredoninae), Part 2. Species of Incastigmus Finnamore. Journal of Hymenoptera Research 11 (1):12-71. (distribution).