Wingless insects are primitive insects that do not fly and have no evolutionary history of flying. They belong to the subclass Apterygota of the class Insecta of the phylum Arthropoda. The orders of this subclass are Archaeognatha and Thysanura. The subclass gets its name from the Greek word meaning "without wings."
Wingless insects do not undergo metamorphosis, or the total change from one developmental stage to another. Instead, nymph forms of these apterygote insects appear to be smaller versions of adults. Apterygotes have small appendages on some of their abdominal segments. Wingless insects continue to molt throughout their lives. Apterygote insects have been wingless throughout evolution, while some currently wingless insects, such as fleas, are descended from winged insects. While wingless insects cannot fly, they can glide in a directed aerial descent from heights. Males do not fertilize females internally. Instead, they deposit sperm packages, called spermatophores, in places where the females will find them.
One order of wingless insects is Archaeognatha, which includes jumping bristletails. These insects have mandibles that connect in only one spot, allowing them to effectively remove algae and lichen. Silverfish and firebrats belong to the order Thysanura. Silverfish are well-known for being fast-running and adaptable to domestic environments. Thysanurans can live up to 3 years.