The phyline plant bug genus Tytthus Fieber, previously containing 19 species, is revised. Isoproba Osborn and Drake, 1915, incorrectly placed in the subfamily Bryocorinae, tribe Dicyphini, is synonymized as a junior synonym of Tytthus Fieber, syn. n.; the only included species, Isoproba picea Osborn and Drake is transferred to Tytthus, comb. n., as the senior synonym of T. hondurensis Carvalho, syn. n.; and T. koreanus Josifov and Kerzhner, 1972 is synonymized with T. chinensis (Stål 1860), syn. n.; and a lectotype for T. parviceps is designated. The six new species T. femoralis from Cuba, Ecuador, Guatemala, Jamaica, Mexico, and Peru, T. fuscicornis from New Mexico (USA), T. mexicanus from Mexico, T. pallidus from Brazil and Panama, T. uniformis from Arizona and New Mexico (USA), and T. wheeleri from the eastern United States are described, bringing the total number of species for the genus to 24. A color adult habitus illustration of T. wheeleri, color photographs for each species (except T. juturnaiba Carvalho and Wallerstein), illustrations of male genitalia, scanning electron photomicrographs of selected structures of certain species, and an identification key are provided to facilitate species recognition. A phylogenetic analysis is offered to help infer relationships.
