Larva vs pupa — WhatDiffers

Short answer

In insects with complete metamorphosis, a larva is the immature stage that feeds and grows; a pupa is the later stage during which the insect develops into its adult form. The sequence is egg → larva → pupa → adult. A caterpillar is a larva, and a butterfly chrysalis is a pupa. 1 2

A pupa is an animal at a particular stage, not necessarily an animal inside a cocoon. Nor does “pupa” mean motionless: mosquito pupae can move quickly through water even though they do not feed. 2 3 4

On this page

At a glance

Question	Larva	Pupa
Position in complete metamorphosis	After the egg, before the pupa.	After the larva, before the adult.
Main role	Feeding and growth.	Development of the adult form.
Feeding	Usually the main feeding stage before adulthood.	Generally does not feed.
Is it necessarily still?	No; many larvae move actively.	No; mosquito pupae can tumble through water.
Butterfly example	Caterpillar.	Chrysalis.
Mosquito example	Aquatic larva, often called a wiggler.	Aquatic pupa, capable of tumbling.
Is a cocoon required?	No; some larvae spin one before pupating.	No; a cocoon is an optional surrounding structure.
Does every insect have this stage?	No; insects with incomplete metamorphosis have nymphs instead.	No; incomplete metamorphosis has no pupal stage.

Sources: insect development 1; butterfly and moth terminology 2; mosquito larvae and pupae 3 4.

What each thing is

A larva, in the insect life cycle discussed here, is the immature stage between hatching and pupation in complete metamorphosis. Its form differs from the adult’s. The plural is larvae. Caterpillars and mosquito larvae are examples, even though their shapes and habitats differ substantially. 1 2 3

A pupa is the developmental stage between larva and adult in these insects. The plural is pupae. Adult structures develop during this transition. A butterfly’s pupa is called a chrysalis; that word names the pupa itself. 1 2

A cocoon is different: it is a covering made around some pupae, typically from silk produced by the larva. Naming the covering does not tell you that the covering and the animal are the same structure. A moth can have a pupa inside a cocoon; a butterfly chrysalis is already the pupal animal. 2

Key differences

The stages have different places in the life cycle. A larva becomes a pupa; a pupa becomes an adult. They are not two kinds of insect, competing classifications, or interchangeable names for anything small and undeveloped. 1

Growth and transformation are organized differently. Larvae feed and grow through successive molts, shedding their outer covering as they increase in size. The pupal stage is the transition in which the adult form develops. Calling it a resting stage can describe its quiet appearance, but it should not imply that development has stopped. 1 2

The same species can look very different at the two stages. In a butterfly life cycle, a caterpillar and chrysalis represent the same developing individual at different times. The change is more than a caterpillar becoming larger. 2

How to tell them apart

Use a species-specific life cycle and the animal’s structure, not one behavior alone. A feeding caterpillar is a larva. A recognized butterfly chrysalis is a pupa. In mosquitoes, the aquatic stages have different body forms, but both can move. The CDC’s life-cycle illustrations show larvae and pupae separately. 2 3

“It moved, so it must be a larva” fails because mosquito pupae can tumble rapidly. “It did not eat while I watched, so it must be a pupa” is also too weak: a short observation does not establish a developmental stage. Movement or a brief lack of feeding cannot replace identification of the animal and its life cycle. 3 4

Size is not a reliable shortcut across species. These words specify stages, not a universal scale on which every larva must be smaller than every pupa.

Where they overlap

Both are immature stages before adulthood in complete metamorphosis. Both are alive and developing. In mosquitoes, both occur in water; sharing a habitat therefore does not make them the same stage. 1 3

The stages also belong to one continuous life history. Describing the larva as the feeding stage and the pupa as the transformation stage highlights their usual roles. It does not mean larvae undergo no development or that a pupa is simply an empty wrapper. 1 2

Edge cases

A pupa can be mobile. Texas A&M’s mosquito life-cycle resource describes nonfeeding pupae that move quickly when disturbed. Immobility is therefore not part of the definition. 4

A cocoon can obscure the stage inside. Some moth caterpillars spin cocoons before becoming pupae. An external silk covering names a structure; the animal inside must be considered separately. 2

Not every insect passes through a pupa. In incomplete metamorphosis, the sequence is egg → nymph → adult. Nymphs molt as they grow, but there is no intervening pupal stage. Treating every immature insect as a larva would erase this difference. 1

Why the distinction exists

The terms distinguish separate stages in a particular developmental pattern. Complete metamorphosis includes a pupal transition; incomplete metamorphosis does not. This makes “larva versus pupa” a question about the animal’s development, rather than its age in days or its position inside a shelter. 1

Examples and common misconceptions

Observation	Correct interpretation
A caterpillar feeding on its host plant	Larval stage.
A butterfly chrysalis attached to a support	Pupal stage, not a separate case containing a pupa.
A mosquito pupa tumbling underwater	A moving pupa, not evidence that it is still a larva.
An insect life cycle labeled egg, nymph, adult	Incomplete metamorphosis; no pupal stage.

These examples illustrate developmental categories. 1 2 4

Sources

Sources checked October 3, 2026. Scope: insect complete metamorphosis, with butterfly and mosquito examples.

Purdue Extension — Understanding Insect Metamorphosis. Complete and incomplete life cycles and larval molts.
Florida Museum of Natural History — Butterfly FAQ. Caterpillars, pupae, chrysalises, and cocoons.
CDC — Life Cycle of Culex Mosquitoes. Aquatic larvae and nonfeeding pupae.
Texas A&M AgriLife Extension — Mosquito Safari: Pupa. Active movement by mosquito pupae.