Halictus lævissimus (Smith, 1853):72, ♀. ♀, Aretic America, Sout of Lake Winnepeg (Dr. Richardson); Cockerell, 1905Cockerell, T.D.A. 1905. Notes on some bees in the British Museum. Transactions of the American Entomological Society 31:309-364.:351, Type ♀ (British Museum). - As Dialictus laevissimus: - Mitchell, 1960Mitchell, T.B. 1960. Bees of the Eastern United States. Volume I. Technical bulletin (North Carolina Agricultural Experiment Station) 141:1-538. (distribution), 401 (comb. nov.). - As Lasioglossum laevissimum: - Owens et al., 2018Owens, B.E., L. Allain, E.C. van Gorder, J.L. Bossart & C.E. Carlton 2018. The bees (Hymenoptera: Apoidea) of Louisiana: An updated, annotated checklist. Proceedings of the Entomological Society of Washington 120 (2):272-307. (distribution); Corbin et al., 2021Corbin, L.A.-J., D.N. Awde & M.H. Richards 2021. Phenological and social characterization of three Lasioglossum (Dialictus) species inferred from long-term trapping collections. Journal of Hymenoptera Research 88:17-38. (biology, distribution).
Halictus smilacinae Robertson, 1899:322, ♀. Robertson, 1897Robertson, C. 1897. North American bees - Descriptions and synonyms. Transactions of the Academy of Science of St. Louis 7 (14):315-356.:323, 2 ♀♀, Illinois. Synonymized with Dialictus laevissimus Smith, 1853 by Mitchell, 1960Mitchell, T.B. 1960. Bees of the Eastern United States. Volume I. Technical bulletin (North Carolina Agricultural Experiment Station) 141:1-538.:401.
Halictus euryceps Ellis, 1914:98, ♀.New Mexico. Synonymized with Dialictus laevissimus Smith, 1853 by Mitchell, 1960Mitchell, T.B. 1960. Bees of the Eastern United States. Volume I. Technical bulletin (North Carolina Agricultural Experiment Station) 141:1-538.:401. - Cockerell, 1919Cockerell, T.D.A. 1919. The bees of Peaceful Valley, Colorado. Journal of the New York Entomological Society 27:298-300. (distribution); Sandhouse, 1924Sandhouse, G.A. 1924. New American species of bees belonging to the genus Halictus (Chloralictus). Proceedings of the United States National Museum 65 (2532):1-43. (distribution); Michener, 1936Michener, C.D. 1936. On certain Halictidae from Northern California. The Pan Pacific Entomologist 12 (4):165-172. (distribution); Cockerell, 1936Cockerell, T.D.A. 1936. Bees from Northern California. The Pan-Pacific Entomologist 12 (3):133-164. (distribution).