What do we call the immature form of insects that undergo gradual metamorphosis?

The immature form of insects that undergo gradual metamorphosis is called a nymph. In this type of metamorphosis, common in certain groups of insects such as hemipterans (true bugs) and orthopterans (grasshoppers), the young resemble smaller versions of the adult, lacking wings or reproductive structures. Nymphs develop through a series of molts, during which they grow and gradually acquire adult characteristics.

The term larva is typically used for immature stages of insects that undergo complete metamorphosis, such as butterflies and beetles, where the larval stage looks completely different from the adult. Pupa refers to the stage in complete metamorphosis where the insect is in a transformed state, often enclosed and undergoing significant change to become an adult. Naiad is a term used specifically for the aquatic immature forms of certain insects, such as dragonflies and mayflies, and usually indicates a specific type of environment or developmental process.