Protepeolus singularis Linsley & Michener, 1937:76, ♀. Linsley & Michener, 1937Linsley, E. G. & C.D. Michener 1937. Some new genera and species of North American parasitic bees. The Pan Pacific Entomologist 13 (1-2):75-84.:77, Holotype ♀, Albuquerque, New Mexico, September 1-3, 1935 (Calif. Acad. Sci. Ent., No. 4344, leg. Michener); Roig-Alsina & Rozen, 1994Roig-Alsina, A. & J.G. Rozen 1994. Revision of the cleptoparasitic bee tribe Protepeolini, including biologies and immature stages (Hymenoptera: Apoidea: Apidae). American Museum Novitates 3099:1-27.:25, Holotype ♀ (California Academy of Sciences). - Eickwort & Linsley, 1978Eickwort, G.C. & E.G. Linsley 1978. The species of the parasitic bee genus Protepeolus (Hymenoptera: Anthophoridae). Journal of the Kansas Entomological Society 51 (1):14-21. (distribution). - As Leiopodus singularis: - Roig-Alsina & Rozen, 1994Roig-Alsina, A. & J.G. Rozen 1994. Revision of the cleptoparasitic bee tribe Protepeolini, including biologies and immature stages (Hymenoptera: Apoidea: Apidae). American Museum Novitates 3099:1-27. (distribution); Ruíz-Cancino & Coronado-Blanco, 2002Ruíz-Cancino, E. & J.M. Coronado-Blanco 2002. Artrópodos terrestres de los estados de Tamaulipas y Nuevo León, México. Serie Publicaciones Cientificas No. 4:1-376. (distribution); Esperanza de Pedro, 2021Esperanza de Pedro, D. 2021. . :. (distribution); Nava-Bolaños & Osorio-Olvera, 2022Nava-Bolaños, A. & L. Osorio-Olvera 2022. Estado del arte del conocimiento de biodiversidad de los polinizadores de México. Revista Mexicana de Biodiversidad 93:1-77. (distribution).
Protepeolus integer Linsley, 1939:4, ♂. Holotype ♂, Douglas, Arizona, August 18, 1935 (Coll. P.H. Timberlake, leg. W.W. Jones); Roig-Alsina & Rozen, 1994Roig-Alsina, A. & J.G. Rozen 1994. Revision of the cleptoparasitic bee tribe Protepeolini, including biologies and immature stages (Hymenoptera: Apoidea: Apidae). American Museum Novitates 3099:1-27.:25, Holotype ♂ (California Academy of Sciences). Synonymized with Protepeolus singularis Linsley & Michener, 1937 by Eickwort & Linsley, 1978Eickwort, G.C. & E.G. Linsley 1978. The species of the parasitic bee genus Protepeolus (Hymenoptera: Anthophoridae). Journal of the Kansas Entomological Society 51 (1):14-21.:15. - Hurd & Linsley, 1963Hurd, P.D. Jr. & E.G. Linsley 1963. Contribution to the systematics of the bee genus Protepeolus Linsley and Michener (Hymenoptera: Apoidea). Journal of the Kansas Entomological Society 36 (4):253-255. (distribution); 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); Roig-Alsina & Rozen, 1994Roig-Alsina, A. & J.G. Rozen 1994. Revision of the cleptoparasitic bee tribe Protepeolini, including biologies and immature stages (Hymenoptera: Apoidea: Apidae). American Museum Novitates 3099:1-27.:25 ( listed as synonym of Leiopodus singularis (Linsley & Michener, 1937)).