The Neopsini encompasses two genera, both exclusively Neotropical: Neopsis Oman (5 species) and Nollia n. gen. (2 species). Neopsis amazonica n. sp., Neopsis tumidifrons n. sp., Neopsis magna n. sp. (Brazil), and Nollia rustica n. sp. (Chile) are described, and the genera and species of the Neopsini are keyed.The New-World Macropsini encompasses five genera: Pediopsis Burmeister (1 species), Pediopsoides Matsumura (2 species), Reticopsis Hamilton (2 species), Macropsis Lewis (55 species), and Oncopsis Burmeister (36 species). Biological and morphological data are used to define the species in this taxonomically difficult tribe, with the result that 45 new species are described: Macropsis acapulco, M. dimorpha, M. igniscutellata, M. mexicana, M. oncopsimilis, and M. zebra from Mexico; Macropsis aureocephala, M. californiensis, M. ferrax, M. inversalis, M. palustris, M. pulchra, Oncopsis arizona, O. aureostria, and Reticopsis udrobates from southern California and Arizona; Oncopsis insignifica, O. mica, and O. tangenta from Utah; Macropsis borealis, M. rufescens, Oncopsis albicollis, O. incidens, O. interior, O. juno, O. marilynae, O. monticola, and O. tenuifoliae from northwestern North America; Macropsis dixiensis and O. infumata from southeastern North America; Macropsis decisa, M. jocosa, M. microceps, M. tunicata, M. xena, Oncopsis citrella, O. concurrens, O. dentata, O. deluda, O. prolixa, O. quebecensis, and O. vartyi from northeastern North America; and Macropsis deviridis, Oncopsis citra, O. crispae, and O. prairiana from Canada. Five new subspecies are described: O. cinctifrons kootenensis, O. prairiana ferrosus, and O. prairiana occidentalis, all from southern British Columbia; Oncopsis nigrinasi florida from Florida; and Macropsis deviridis alberta from western Canada. Five new synonymies are created. Keys to all taxa, host associations, and distribution maps are provided and the colour phases of the various polymorphic species are analyzed.The morphology and significance of intersex individuals of Oncopsis spp. are discussed.