Palaeodictyoptera is an extinct order of insects including all the Palaeozoic and a few Triassic species. The order was founded by Scudder, and, as formally diagnosed, it includes a group of insects with an incomplete metamorphosis, two pairs of wings which are equal in size, membranous in texture, and simple in the arrangement of the thickened lines usually known as "nerves"; their characters are therefore of a simple primitive type. The value of the order is, however, very doubtful, and it appears most probable that it will have to be split up among the four orders of Orthoptera (cockroaches, etc.). Neuroptera (mayflies, etc.), Hemiptera and Coleoptera (or beetles). Thus the oldest known insect Palaeoblattina, and the Carboniferous cockroach Progonoblattina, and the old "stick-insect" Protoplasmida appear to be primitive forms of the Orthoptera. Platephemera is probably an old member of the Ephemeridae or May-flies. Lithomantis and Miamia are also both allied to the Neuroptera. The Hemiptera or Rhynchota is represented by the Permian Eugereon and Fulgorina, and the Coleoptera by some beetle's wing cases or elytra and some borings in the Carboniferous.