The long-horn bee genus Tetralonia consists of 35 Western Palaearctic species that are associated mostly with the family Asteraceae as host plants. A minority of the species are, however, exclusively associated with other host plants that have particularly large pollen grains, such as those in the plant families Caprifoliaceae, Malvaceae, and Onagraceae. This work presents a taxonomic account and morphological description of the assemblages of Tetralonia species with atypical (non- Asteraceae) host plants. It includes a key to the pollinosa-group, which contains most of the species, a description of three regionally restricted new species, namely T. eoacinctella Dorchin sp. nov., T. epilobii Dorchin sp. nov., and T. stellipilis Dorchin sp. nov., a lectotype designation for Eucera cinctella Saunders, 1908 [=Tetralonia cinctella (Saunders, 1908)], and a neotype designation for Apis malvae Rossi, 1790 [=Tetralonia malvae (Rossi, 1790)]. In addition, the name Eucera macroglossa Illiger, 1806 is confirmed as a synonym of Apis malvae Rossi, 1790; Tetralonia macroglossa ssp. xanthopyga Alfken, 1936 is officially placed in synonymy with Apis malvae Rossi, 1790; and Macrocera confusa Pérez, 1902 is listed as a doubtful synonym of Tetralonia scabiosae Mocsàry, 1879 (syn. nov.).