How does a Caterpillar turn into a Butterfly?

The beautiful winged insects we recognise as butterflies are actually in the fourth and final stage of their life cycles. But how did they get there? This article is the first of a two-part series on butterflies.

WHAT ARE BUTTERFLIES?

Butterflies are insects found all over the world, and come in an enormous variety of colours and sizes. It is thought that they were initially named ‘butter-flies’ because they were seen drinking from the open pots used for churning buttermilk. They are insects with a four-stage life cycle in the biological group known as the Lepidoptera. The four stages of the butterfly’s life cycle are:

1. EGG

In most species of butterfly, the female lays 100-200 eggs on a leaf.  These are stuck to the leaf by a very sticky glue-like wax. The type of plant and shape of the egg varies from species to species.

2. CATERPILLAR

After about ten days, the eggs hatch and a worm-like insect will crawl out. Caterpillars spend most of their time eating leaves, so have powerful jaws and large guts.

3. PUPA

When the caterpillar has eaten enough to grow to its full size,  it will find a safe spot like the bottom of a leaf or branch. It builds a hard protective shell around its body called a chrysalis and remains until it is ready to emerge as a butterfly —usually around two weeks later.

4. ADULT BUTTERFLY

The beautiful, winged insects that emerge from the chrysalis don’t have any jaws: unlike caterpillars, they suck nectar from flowers. All species feed, reproduce, lay their eggs and die, but their lifespans can vary from 24 hours to two years!

WHAT ACTUALLY HAPPENS DURING THE PUPAL STAGE?

First, the caterpillar produces chemicals called enzymes which fill the pupa and break down its body much like the acids in your stomach break down the food you eat. This continues until only a few solid parts (called the imaginal discs) remain. These discs correspond to the main body parts of an adult butterfly or moth, so there is a disc for each of the wings, a disc for each of the legs, one for the abdomen, one for each of the antennae, one for each eye and so on. The ‘soup’ of digested caterpillar starts to form the new body parts using each of these discs as a base until an adult butterfly emerges from the chrysalis or cocoon about two weeks later. The process of complete body change is called metamorphosis —another example of this is when a tadpole changes into a frog.  

BUTTERFLIES AND MOTHS

In the next article of this two-part series, read about the difference between butterflies and moths!

ALICE DOYLE

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