The genera Scotobius (Tenebrioninae) and Nyctelia (Pimeliinae), both widely distributed in southern South America, are two of the three most species-rich genera in Argentina and constitute the type genera of the tribes Scotobiini and Nycteliini respectively. Study of type material from species described by Billberg (1815) and Germar (1823), as well as bibliographical research, indicates the need for nomenclatural changes in both genera. A new synonymy within the genus Scotobius Germar, 1823 is proposed: Scotobius crispatus Germar, 1823 with S. miliaris (Billberg, 1815). Scotobius brevicollis Kulzer, 1955 stat. n., originally described as a subspecies of S. crispatus, is elevated to species status. Scotobius pilularius Germar, 1823 is restored from its synonymy with S. miliaris and is the valid name of the type species of the genus. Supporting references are included for the preservation of the genus name Nyctelia Berthold, 1827 (22 September) nom. protectum, which is given precedence over Nyctelius Guérin-Méneville, 1827 (18 August) nom. oblitum under Article 23.9. Zophosis picipes Billberg, 1815 is restored from its synonymy with Nyctelia brunnipes Latreille, 1804 (correct year 1828) and transferred to the genus Nyctelia. Six new synonymies are proposed: Nyctelia nodosa (Germar, 1823) with N. picipes (Billberg, 1815), N. brunnipes Guérin-Méneville, 1834 with N. picipes (Billberg, 1815), N. nigripes Solier, 1836 with N. picipes (Billberg, 1815), N. aequicostata Solier, 1836 with N. picipes (Billberg, 1815), N. angustata Waterhouse, 1841 with N. picipes (Billberg, 1815), and N. quadricollis Fairmaire, 1905 with N. picipes (Billberg, 1815). Based on the these synonymies, the valid name for Zophosis nodosa, the type species of Nyctelia by monotypy, is Zophosis picipes Billberg, 1815. Lectotypes are designated for Scotobius crispatus Germar, 1823, S. pilularius Germar, 1823, S. varicosus Germar, 1823 and Zophosis nodosa Germar, 1823. Scotobius pilularius is recorded for the first time in Chile.