Apterygote

apterygote, broadly, any of the primitive wingless insects, distinct from the pterygotes, or winged insects. Used in this sense, the term apterygote commonly includes the primitive insects of the following groups: proturans, collembolans (springtails), diplurans, and species in the orders Zygentoma, Archaeognatha, and Monura (formerly the thysanurans).

Protura

The taxonomic status of the various groups that are considered apterygotes, however, remains unsettled. A typical apterygote, for example, is wingless and has six legs. The presence of six legs was once an important feature in the identification of true insects and enabled the identification of the apterygotes, including the proturans, collembolans, and diplurans and the now defunct Thysanura—the four groups that together made up the traditional subclass Apterygota (class Insecta). However, the proturans, collembolans, and diplurans are now considered by some entomologists to be offshoots from the main insectan stem of evolution and have been given independent taxonomic status as classes equivalent to the class Insecta. The term apterygote, therefore, is sometimes applied only to those groups thought to be ancestors of pterygotes—i.e., the silverfish, fishmoths, and firebrats (order Zygentoma) and the bristletails (order Archaeognatha), together with the extinct monurans (order Monura). For completeness of discussion, however, and because of the similarities of these primitive hexapods, the proturans, collembolans, and diplurans, as well as orders Zygentoma, Archaeognatha, and Monura, are included in this article.