The transformation of a caterpillar into a butterfly or moth is one of the more amazing processes to witness. It’s as if one creature becomes something else entirely.
However, we know that caterpillars become butterflies or moths as a normal part of their life cycle. There's nothing mysterious or magical about it. It is science in action.
A key part of their transformation is a chrysalis or cocoon. The two words are often used interchangeably, but they 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.
Words to know
Exoskeleton: A rigid external covering common in arthropods that supports an animal's body.
Hemimetabolous: A form of insect development with three distinct life stages.
Holometabolous: A form of insect development with four distinct life stages.
Metamorphosis: The process of transformation from an immature form to an adult form.
To better understand, let's take 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. The larva then becomes a pupa, which is the transitional stage. After the transition, the adult butterfly or moth emerges.
It's this transitional pupal stage where chrysalises and cocoons are essential for the change into a butterfly or moth. However, only butterflies use a chrysalis and only moths use a cocoon. In the pupal stage, a caterpillar transforms into a butterfly in a chrysalis. A moth uses a cocoon for its pupal transformation.
This transformation is called metamorphosis. It happens inside a chrysalis for butterflies and inside a cocoon for moths. Although they are used for the same purpose, chrysalises and cocoons are actually quite different.
A chrysalis is an exoskeleton, which is a hard, smooth covering surrounding the insect inside as it transforms to a butterfly. Moths spin cocoons from silk, covering themselves in a soft, silky layer.
How long it takes for adult moths and butterflies to emerge from their cocoons and chrysalises varies depending on the species. It typically takes between five and 21 days.
Both chrysalises and cocoons offer protection for the insects as they undergo metamorphosis. Where we may find them differs. Chrysalises are usually found hanging from a structure, and cocoons are typically buried in the ground, 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 they undergo complete metamorphosis in each of the four stages of their lives. Some insects have a life cycle that is three phases. They do not undergo complete metamorphosis and instead go through gradual changes in size and form. These insects, which include dragonflies, grasshoppers and crickets, are said to be hemimetabolous.
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