Which insect type is characterized by a lack of metamorphosis?

The insect type characterized by a lack of metamorphosis is the silverfish. Silverfish belong to a group of insects known as ametabolous insects, meaning they undergo a form of development that does not involve major transformation stages like larva or pupa. Instead, silverfish hatch from eggs and resemble miniature adults as nymphs. These nymphs grow into adults through a series of molts without undergoing drastic changes in form or structure.

In the case of cockroaches, fleas, and wasps, these insects exhibit metamorphosis. Cockroaches undergo a gradual metamorphosis but still pass through distinct life stages, including nymphs that undergo molts to eventually become adults. Fleas and wasps, on the other hand, undergo complete metamorphosis, where they pass through distinct egg, larval, pupal, and adult stages. Silverfish's unique developmental process highlights their classification as ancient insects and contributes to their specific ecological role.