Four new species of Plega Navás, 1928 (Mantispidae: Symphrasinae) from Mexico are herein described and illustrated, namely P. mixteca sp. n. from Oaxaca and Jalisco, P. stangei sp. n. from Morelos and Oaxaca, P. sonorae sp. n. from Sonora, and P. spinosa sp. n. from Guerrero, Jalisco, Morelos, Nayarit, Oaxaca, Puebla, and Veracruz. Including these new species, Plega's diversity raises to 17 described species, of which 12 are recorded from Mexico, and one of them, Plega variegata Navás, 1928, is herein proposed as nomen dubium. A taxonomic key to the known species of Plega from Mexico is provided.
Keywords: Neuroptera, Symphrasinae, mantidflies, Neotropics, taxonomy, morphology.