Species of the thorny lacewing subfamily Symphrasinae (Neuroptera: Rhachiberothidae) are revised. Prior to this work, 42 species were known in the genera Anchieta Navás, 1909, Plega Navás, 1928, and Trichoscelia Westwood, 1852. Herein, the number of species is increased to 60, 23 of which are newly described. Species previously known are redescribed, and their taxonomic status is revised. Keys, diagnoses, and high-resolution images for all species are presented. The distribution range of Anchieta is now known from Costa Rica to southern Brazil with a total of 11 species, of which three are newly described. The genus Plega is known from southwestern United States to southern Brazil and includes 28 species of which 14 are described as new. Moreover, the genus Trichoscelia occurs from central and southern Mexico to Argentina, with a total of 21 species, of which six are herein newly described. A phylogenetic analysis of Symphrasinae based on morphological characters recovered the three symphrasine genera as monophyletic, with Anchieta sister to Plega + Trichoscelia. The three genera are newly diagnosed based on a cladistic framework. Within the genus Anchieta, bee-mimicking species comprise a monophyletic group, while wasp-mimicking species form a laddered sequence to that lineage. Within Plega, three lineages are recovered, the first mostly composed of South and Mesoamerican species, the second with species predominantly from Central America and central and southern Mexico, and a third clade encompassing species mostly from central and northern Mexico and southwestern United States. By contrast, relationships between species of Trichoscelia were poorly resolved because of a simplified and conserved morphology of this group.
