Immature

Definition

Not having reached sexual maturity; describing a life stage or individual that has not yet developed functional reproductive organs or completed the morphological and physiological changes required for breeding. In arthropods, immature stages typically precede the adult (imago) and may encompass eggs, larvae, nymphs, or juveniles depending on developmental mode. The term contrasts with mature or adult and is often used quantitatively (e.g., 'proportion of immature females') or qualitatively to stage specimens.

Etymology

Latin immaturus, from in- 'not' + maturus 'ripe, timely'

Example

In field populations of Ixodes scapularis (black-legged tick), immature nymphs dominate spring collections, whereas mature adults appear in autumn when they seek hosts for reproduction.

Synonyms

• Juvenile
• larval
• nymphal

Related Terms

• mature
• Adult
• Imago
• instar
• life stage
• ontogeny
• subadult
• preadult

Usage Notes

In entomology, immature is broader than larval (restricted to holometabolous insects) or nymphal (restricted to hemimetabolous insects and some arachnids). It is often preferred in ecological and demographic studies where precise developmental stage is unknown or variable across species. Some authors restrict immature to active feeding stages, excluding eggs; others use it inclusively. The term carries no implication about size—some immature arthropods (e.g., cicada nymphs) may be larger than conspecific adults. Contrast with subadult, which typically denotes a late immature stage immediately preceding maturity.