The Endopterygota, also known as Holometabola, are insects of the subclass Pterygota which go through distinctive larval, pupal, and adult stages. They undergo a radical metamorphosis, with the larval and adult stages differing considerably in their structure and behaviour. This is called holometabolism, or complete metamorphism.
The Endopterygota are among the most diverse insect superorders, with at least 680,000 living species divided between eleven orders, containing insects such as butterflies, fleas, bees, ants and beetles.
They are distinguished from the Exopterygota (or Hemipterodea) by the way in which their wings develop. Endopterygota (meaning literally "internal winged forms") develop wings inside the body and undergo an elaborate metamorphosis involving a pupal stage. Exopterygota ("external winged forms") develop wings on the outside of their bodies and do not go through a pupal stage. The latter trait is plesiomorphic however and not exclusively found in the exopterygotes, but also in groups such as Odonata (dragonflies and damselflies) which are not Neoptera but more basal among insects.
The Endopterygota are sometimes divided into three assemblages: Neuropteroida (Neuroptera, Megaloptera, Raphidioptera and Coleoptera), Hymenopteroida (Hymenoptera), and Panorpoida (Siphonaptera, Diptera, Trichoptera, Lepidoptera, Strepsiptera and Mecoptera). It was long believed that the hymenopterans, with their highly-developed social systems, constituted the most advanced insects, despite their rather "primitive" anatomy compared to flies and beetles for example.
More recently, this is increasingly been rejected and DNA sequence data seems to verify that the hymenopterans are indeed among the most basal endopterygotes, whereas flies and fleas are often considered the most radically advanced insects nowadays. This calls the previous subdivision into question, and consequently several new taxa have been proposed, splitting up the Endopterygota. While some groups (such as the "sucking-stinging" fly-flea assemblage or the caddisfly-butterfly group) seem indeed to be good clades, it is not likely that the relationships of the endopterygotes, or the neopteran insects in general, will be resolved in detail soon.
Superorder Endopterygota sensu stricto
Proposed superorder Amphiesmenoptera