pupa - Chrysalis, Cocoon, Further reading

The life-cycle stage of an insect during which the larval form is reorganized to produce the definitive adult form. It is commonly an inactive stage, enclosed in a hard shell (chrysalis) or silken covering (cocoon).

A pupa (Latin pupa for doll, pl: pupae or pupas) is the life stage of some insects undergoing transformation.

The pupal stage occurs only in holometabolic insects, those that undergo a complete metamorphosis, going through four life stages;

It is during the time of pupation, that the adult structures of the insect are formed whilst the larval structures are broken down.

Pupation may be brief, for example 2 weeks as in monarch butterflies, or the pupa may enter dormancy until the appropriate season for the adult insect returns (in temperate climates pupae usually stay dormant during winter, in the tropics pupae usually do so during the dry season).

Insects emerge (eclose) from the pupa by splitting the pupal case, and the whole process of pupation is controlled by the insect's hormones.

In some insect orders the appendages such as legs and proboscis are free and visible in the pupal stage.

Moth pupae are usually dark in color and either formed in underground cells, loose in the soil, or their pupa is contained in a protective silk case called a cocoon.

Chrysalis

A chrysalis (Latin chrysallis, from Greek χρυσαλλίς = chrysallís, pl: chrysalids) or nympha is the pupal stage of butterflies.

Because chrysalids are often showy and are formed in the open they are the most familiar examples of pupae.

Like other types of pupae the chrysalis stage in most butterflies is one in which there is little movement.

Cocoon

A cocoon is a casing spun of silk by many moth caterpillars and numerous other holometabolous insect larvae as a protective covering for the pupa.

Cocoons may be tough or soft, opaque or translucent, solid or meshlike, of various colors, or composed of multiple layers, depending on the type of insect larva producing it.

Insects that pupate in a cocoon must escape from it, and they do this either by the pupa cutting its way out, or by secreting fluids that soften the cocoon.

Silkworm cocoons are processed and used to produce natural silk for clothing.

An Emperor Gum Moth caterpillar spinning its cocoon.	Luna moth cocoon and pupa.	Assortment of Luna moth cocoons.	Luna moth eclosing from silk cocoon.
Luna moth pupa removed from cocoon.	Chrysalis of Gulf Fritillary in Georgetown, South Carolina	Pupation of Inachis io	Monarch Butterfly chrysalis

Further reading

For moth and butterfly pupae, see Malcolm J.