Pterygota plural proper noun - winged insects, formerly a subclass of
Insecta, not now considered a valid taxonomic grouping, though the term is still used in an informal sense. The group Pterygota comprises the majority of insects, and the ones most often encountered. The most commonly encountered non-winged insects belong to the orders
Zygentoma (Silverfish) and
Microcoryphia (Bristletails). Pterygota have veined wings on the second and third thoracic segments. Some members of the Pterygota have secondarily lost wings. This occurs when a lifestyle, such as parasitism, or subterranean life, makes wings, and flight, disadvantageous. There are examples in many groups. In these cases, wingless forms have close relatives with wings.
According to this
Tree of Life article there are three prominent evolutionary lines of living winged insects:
2-
Odonata--dragonflies and damselflies
3-
Neoptera--all other winged insects. These have a sophisticated mechanism for folding the wings over the back.
Sometimes Ephemeroptera and Odonata are placed in a group, the
Paleoptera (old-winged), though others have placed these, in various combinations, with the Neoptera. An important group under the neoptera is
Endopterygota (Holometabola), insects with complete metamorphosis. This includes the neuroptera and subsequent orders in the traditional classification.
