The subphylum Hexapoda (from Greek for ‘six legs’) is the largest (in terms of number of species) grouping of arthropods and includes two classes: the Insecta (Ectognatha) and the Entognatha. This last class groups three small orders of wingless hexapods: Collembola, Protura, and Diplura.

Hexapods comprise insects and three small orders of insect-like animals with six thoracic legs. They are sometimes grouped with the myriapods, in a group called Uniramia, though genetic evidence tends to support a closer relationship between hexapods and crustaceans.