Nature on our doorsteps – The magic of cocooning

Nature on our doorsteps – The magic of cocooning

By Rosaleen Dwyer

Rosaleen Dwyer is the County Heritage Officer at South Dublin County Council – every week she gives us an insight into the natural heritage around us and the beautiful biodiversity of the plants and creatures

The transformation of a caterpillar into a butterfly or a moth is a fascinating process.

When fully grown, the caterpillar of a butterfly attaches itself to the underside of a leaf or a twig using short silky threads.

A newly emerged Six spot Burnett Moth 1

A newly emerged Six-spot Burnet Moth

It sheds its outer skin and the new skin underneath hardens into a protective structure called a chrysalis.

Moth caterpillars generally spin long silken threads, wrapping this around themselves again and again to form a cocoon.

The chrysalis or the cocoon is not a quiet place of rest, however. This is where the magic happens.

To begin the change from a pudgy little caterpillar into an elegant winged adult, special enzymes in the caterpillar’s body start to dissolve all its organs and tissues, from the inside out.

Certain important groups of cells survive, floating amongst the soupy, protein-rich fluid.

The Six spot Burnet Moth attaches its yellow cocoons to plant stems 1

Six-spot Burnet Moth attaches its yellow cocoons to plant stem

These cells trigger the growth of parts of the new adult insect like the wings, eyes, and long legs.

The transformation process takes between two or three weeks to complete, or longer if the insect overwinters in this form.

The new adult emerges through a cut in the wall of the cocoon or chrysalis.

It pauses to fully expand and dry its wings, and off it goes.

In nature at least, the ‘cocooning’ process certainly cannot be described as a boring, tiresome period of confinement.

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