When hatched, the young closely resemble adults and do not undergo any significant metamorphosis, and lack even an identifiable nymphal stage.

Apterygotes possess small unsegmented appendages, referred to as "styli", on some of their abdominal segments, but play no part in locomotion.

[6] While all members of winged insects (Pterygota) has a closed amniotic cavity during embryonic development, this varies within Apterygota.

The most notable synapomorphy proving the monophyly of Thysanura+Pterygota is the absence of intrinsic antennal muscles, which connect the antennomeres in entognaths, myriapods, and crustaceans.

However, the Zygentoma are now considered more closely related to the Pterygota than to the Archaeognatha,[4] thus rendering even the amyocerate apterygotes paraphyletic, and resulting in the dissolution of Thysanura into two separate monophyletic orders.