Six new genera and six new species of Phylinae are described from the western United States and Baja California, Mexico, and two new combinations are created. Most of the species are known to breed on oaks, Quercus spp. (Fagaceae). Galbinocoris caepa, new genus and species, is described from Arizona and Texas. Hamatophylus, new genus, is described to accommodate Plagiognathus guttulosus (Reuter), which breeds on several species of oaks, among them Quercus virginiana Mill. Insulaphylus, new genus, is restricted to the Channel Islands off the coast of southern California, and is described to accommodate Insulaphylus cruz, new species, from Santa Cruz Island and Insulaphylus meridianus, new species, from Santa Catalina and San Clemente Islands. Both species breed on Quercus spp. Maculamiris, new genus, is described with two species, Maculamiris baja, new species, from Baja California and southern California, and Maculamiris insulanus, new species, from the Channel Islands. Both species are associated with rosaceous plants. Quernocoris caliginosus, new genus and species, is described from mainland southern California and the Channel Islands where it breeds on a range of oak species. Vesperocoris, new genus, is described to accommodate the often oak-breeding Plagiognathus paddocki Knight from California.