Juvenile

Definition

An immature individual that has hatched or emerged from the egg but has not yet reached sexual maturity or acquired the adult body plan; in arthropods, juveniles typically resemble smaller, sexually immature versions of adults (hemimetabolous development) or occupy a distinct larval/nymphal form distinct from the adult (holometabolous development).

Etymology

Latin iuvenilis, from iuvenis 'young person'

Example

In the springtail Orchesella cincta, juveniles undergo multiple molts through distinct size classes before reaching reproductive maturity, with each instar showing incremental development of the furcula and body pigmentation.

Synonyms

• Immature
• subadult

Related Terms

• instar
• nymph
• larva
• pupa
• Adult
• Eclosion
• Metamorphosis
• hemimetabolous
• holometabolous
• ontogeny

Usage Notes

In entomology, 'juvenile' often overlaps with 'nymph' (for hemimetabolous insects) or 'larva' (for holometabolous insects), but is broader and emphasizes the immature condition rather than a specific stage name. Some specialists reserve 'juvenile' for post-embryonic, pre-reproductive individuals that lack a discrete pupal phase, using 'larva' and 'pupa' for holometabolous forms. In arachnology, 'juvenile' is standard for all immature instars between the post-embryonic stage and maturity. Contrast with 'adult' (sexually mature) and 'neonate' (newly hatched/emerged, often used for the first instar specifically).