The transformation of a caterpillar into a butterfly or moth is one of the more wondrous processes to witness in the natural world, as one creature becomes what is seemingly another creature entirely.

We know, though, that caterpillars become butterflies or moths as a normal part of their life cycle. There's nothing mysterious or magical about it; it's simply science in motion. A key part of that transformation is a chrysalis or cocoon, but these two things are not one and the same. Instead, each is a part of the life cycle for either a butterfly or a moth, but not both.

To better understand, let's start with a quick look at the life cycle of butterflies and moths. These insects start life as eggs, which are laid by adults. The egg hatches and the insect moves into the larva stage, which for both butterflies and moths takes the form of a caterpillar, according to the Academy of Natural Sciences. The larva then becomes a pupa, which is the transitional stage. After the transition, the adult butterfly or moth emerges. 

WHAT'S THE DIFFERENCE: BUTTERFLY VS. MOTH

It's this transitional pupal stage where both chrysalises and cocoons are essential for the change into a butterfly or a moth, but only butterflies use a chrysalis and only moths use a cocoon. In the pupal stage, a caterpillar transforms into a butterfly in a chrysalis, while a moth uses a cocoon for its pupal transformation, according to the Florida Museum. 

This transformation, called metamorphosis, happens inside a chrysalis for butterflies and inside a cocoon for moths, but chrysalises and cocoons are actually quite different. A chrysalis is an exoskeleton, a hard, smooth covering enveloping the insect inside as it transforms from a caterpillar to a butterfly, according to Monarch Joint Venture. Moths, on the other hand, spin cocoons from silk, encasing themselves in the silky layer.

How long it takes for adult moths and butterflies to emerge from their cocoons and chrysalises respectively varies among species, but it typically takes between five and 21 days. Both chrysalises and cocoons offer protection for the insects as they undergo metamorphosis, and moths' cocoons also provide warmth, the Joint Venture reports. Where we may find them differs, though. Chrysalises are usually found hanging from a structure, while cocoons are typically buried in the ground or in leaf litter or attached to the side of a structure.  

One thing that butterflies and moths have in common is that both are holometabolous, which means that the insects undergo complete metamorphosis in their four life stages, according to the Library of Congress. Some insects do not undergo complete metamorphosis and instead go through gradual changes in size and form. These insects, which include dragonflies, grasshoppers and crickets, among many others, are said to be hemimetabolous.

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