For a list of all of the orders in this key, click here: List of Orders.

Classification note: The diplurans were once considered insects (in the class Insecta), but were removed once scientists determined that they, Protura and Collembola were not in the evolutionary lineage of insects. In other words, these three groups did not give rise to modern-day insects. Scientists are still working out the tree of life for Diplura, Protura and Collembola. Most authorities place them into their own classes: Class Protura, Class Diplura and Class Collembola. Some authorities, however, group them together under one class called Class Entognatha and list them as orders, and still others put only Protura and Collembola in the Class Entognatha and place Diplura in its own class: Class Diplura.