Nomia howardi Crawford, 1911:617 - Cockerell & Blair, 1930Cockerell, T.D.A. & B.H. Blair 1930. Rocky Mountain bees. I. American Museum Novitates 433:1-19. (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); 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).
Nomia howardi vanduzeei Cockerell, 1924:540, ♀. Holotype ♀, Loreto, Lower California, May 20 (Mus. Calif. Acad. Sci., No. 1509, leg. Van Duzee). - Cockerell & Blair, 1930Cockerell, T.D.A. & B.H. Blair 1930. Rocky Mountain bees. I. American Museum Novitates 433:1-19. (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.:1943 ( listed as synonym of Nomia howardi Crawford, 1911).
Nomia californica peninsularis Cockerell, 1930:12 - 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.:1943 ( listed as synonym of Nomia howardi Crawford, 1911).