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Insects and other arthropods

Chrysalis (or pupa)

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“J” shape position

The caterpillar has to find a quiet spot where it can safely turn into a chrysalis. It will usually leave its host plant and go in search of a spot high off the ground, where it will be well camouflaged.

Once it finds an ideal site, the caterpillar weaves a tiny silk pad so that it can anchor itself.

It then firmly inserts the hooks at the tip of its abdomen in the silk pad. Hanging upside down, it pulls itself up slightly into a J shape. It stays in this position for 12 to 48 hours. During this time, its colours turn dull and it loses weight. It almost looks sick. It won’t be long now until it is fully transformed: one last moult, and in less than a minute the chrysalis will appear.

A caterpillar produces its silk with modified salivary glands, in its mouth! Spiders also produce silk, but they use spinners located at the tip of their abdomens.

Invisible beauty

A monarch chrysalis is a real work of art! With its lovely gold-spotted turquoise green colour, it wouldn’t look out of place in a jeweller’s display case.

But in the wild this approximately 3 cm long chrysalis goes unnoticed. Its colour blends in with the vegetation and some of its parts reflect light like a dewdrop glinting in the sun. When you don’t have any means of fleeing your predators, you’d better be well camouflaged!

The gold spots on a monarch chrysalis don’t actually contain any pigment. Their colour is produced by light reflecting off zones of the cuticle made up of alternating light and dark layers.

Changing colours, changing shape

Over the 8 to 15 days that it spends as a chrysalis, the insect changes colour several times. The chrysalis starts out very pale green before turning gold-tinged jade green and then blue. Inside, the butterfly is taking shape. About 24 to 48 hours before it emerges, there’s just one final touch to be added: pigment production. At that point, you can see the orange, white and black of the monarch’s wings through the transparent case.

Chrysalis or cocoon?

The chrysalis is the third stage in a butterfly’s life cycle.

A cocoon is a silk case spun by some caterpillars to protect the insect from nasty weather and predators during the chrysalis stage. This defensive strategy is used by some moths.

Monarchs are butterflies, not moths, and thus don’t spin cocoons, but they still have to go through the chrysalis stage in order to complete their life cycle.

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