Traditional morphology-based systematics have usually given the Hexapoda the rank of superclass, and identified four groups within it: insects (Ectognatha), Collembola, Protura, and Diplura, the latter three being grouped together as the Entognatha on the basis of internalized mouth parts.
The use of phylogenetic data has brought about numerous changes in relationships above the level of orders. Insects can be divided into two groups historically treated as subclasses: wingless insects or Apterygota, and winged insects or Pterygota. The Apterygota traditionally consisted of the primitively wingless orders Archaeognatha (jumping bristletails) and Zygentoma (silverfish). However, Apterygota is not monophyletic, as Archaeognatha are sister to all other insects, based on the arrangement of their mandibles, while the Pterygota, the winged insects, emerged from within the Dicondylia, alongside the Zygentoma.
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