Background: The tribe Lethaeini has received little attention in Argentina. In 2014, Dellapé recorded 9 genera and 15 species from this country.
Results: A comprehensive study of the Lethaeini (Heteroptera, Rhyparochromidae) from Argentina is presented. Herein three new species of Cryphula Stål, one new species of Cistalia Stål, and the male of Cryphula australis Berg aredescribed. The genus PetissiusDistantand the species Cistaliabinotata Slater& Baranowski, Cistalianeotropicalis Slater & Baranowski, and Petissius spinipes Stål are reported for the first time from Argentina; also, the known distribution is extended for many of the previously recorded species. A generic key, keys to species, and distributional maps to the Argentinean species are also given. Dorsal habitus photographs of all species and the male and female genitalia of the new species are provided to facilitateidentification.
Conclusions: The Lethaeini fauna from Argentina is increased to 10 genera and 22 species. The distribution of the tribe in the country is mainly Neotropical into the Chacoan Subregion, with most of the species distributed in the Chacoan and Pampean provinces (Chacoan Domain) and Parana Forest Province (Parana Domain). Only Rhaptus quadricollis appears to be an Andean element, with most of the known records in the South American Transition Zone (Monte Province).
Keywords: Bubaces; Cistalia; Cryphula; Esuris; Lipostemmata; Neopetissius; Rhaptus; Stictolethaeus; Valtissius.