The subphylum
Hexapoda (from the
Greek for
six legs) constitutes the largest number of species of
arthropods and includes the
insects as well as three much smaller groups of wingless arthropods:
Collembola,
Protura, and
Diplura (all of these were once considered insects). The Collembola (or
springtails) are very abundant in terrestrial environments.
Hexapods are named for their most distinctive feature: a consolidated thorax with three pairs of legs. Most other arthropods have more than three pairs of legs.