Halictus perdifficilis Cockerell, 1895:68, ♀. ♀, Santa Fé, N.M., July 4, 1894 (leg. Ckll.). - Cockerell, 1899Cockerell, T.D.A. 1899. Notes on american bees (Concluded from p. 129). The Entomologist 32:154-159. (distribution); Cockerell, 1906Cockerell, T.D.A. 1906. The bees of New Mexico. Transactions of the American Entomological Society 32:289-314. (distribution); Sandhouse & Cockerell, 1924Sandhouse, G. & T.D.A. Cockerell 1924. Expedition of the California Academy of Sciences to the Gulf of California in 1921. The bees (III). Proceedings of the California Academy of Sciences ser. 4: v. 13 (21):333-339. (distribution). - As Dialictus perdifficilis: - 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). - As Halictus perfficilis: - 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.:1969 (!). - As Halictus perfficilis: - 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.:1969 (!). - As Lasioglossum perdifficile: - 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).