Halictus simplex complex: This term is used to collectively refer to the females of three species: Halictus simplex Blüthgen, 1923, H. compressus Walckenaer, 1802, and H. langobardicus Blüthgen, 1944. The females of these species are so similar that in many cases they cannot be distinguished using morphological techniques.

References: Amiet F, Herrmann M, Müller A, Neumeyer R (2001) Fauna Helvetica 9. Apidae 3: Lasioglossum, Halictus. Centre Suisse de Cartographie de la Faune, Neuchatel, Switzerland. 208 pp. Pauly, A. (2017). Clé provisoire pour l'identification des Halictus Latreille, 1804 et Lasioglossum Curtis, 1833 de Belgique (Hymenoptera Apoidea Halictidae).