Background

Butterflies are symbols of change. They transform from caterpillars to beautiful butterfies; and this transformation has inspired people for ages! In this module, you will learn all about this magnificent process.

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Task

Read the following text carefully:

All butterflies and moths share four stages of development. These four stages together make up the life cycle. The change in appearance that they go through in their various stages is called metamorphosis.

EGG > LARVA (or caterpillar) > PUPA > ADULT

Stage One: EGG

Milkweed is the only type of plant that monarch caterpillars can eat, so female monarchs lay eggs on the leaves of milkweed plants.

When a female land on a plant, she checks to see if it’s a milkweed plant by scratching the surface of its leaf with her front legs and inspects the plant juices with her antennae.

When she’s sure that she has landed on milkweed, the monarch lays her eggs.

A female monarch can lay between 100 and 400 eggs in her short lifetime, but she can only lay one fertilized egg per milkweed leaf. For this reason, large groups of milkweed plants can make a big difference to monarch survival.

Stage Two: LARVA (caterpillars)

After three to 12 days, small caterpillars with black, yellow and white stripes hatch from the monarch eggs. First they eat their egg shell, then they feed on milkweed leaves for about two weeks.

During this time, the caterpillar grows by moulting, which means it sheds its tight skin. Moulting happens four times. The stages in between moults are called instars. Monarch caterpillars typically go through five instars.

In the final instar, caterpillars will have reached a length of 2.5 cm to five cm.

Stage Three: PUPA

Now, the caterpillar hooks onto a twig with its head facing down and sheds its skin one last time.

The discarded skin becomes a protective case around the caterpillar.

Within a few hours, the caterpillar becomes a pupa, which is also known as a chrysalis.

The completed chrysalis is bright green, which helps it to blend in with plant leaves. Blending in is a defense against predators, which is important because the chrysalis will not move at all for two weeks.

Stage Four: Adult

The pupa becomes completely transparent in its last hours. Finally, a butterfly emerges. Its wings are small and thick; it can’t fly until it pumps those wings to distribute its bodily fluids.

When its wings are fully dry, the butterfly is ready to fly! The adult butterfly lives for up to 30 days.

Summer monarchs versus winter monarchs

Monarchs in eastern Canada produce two to three generations, or broods, in the summer – generally between June to September. Full metamorphosis of a monarch butterfly can take from 20 to 45 days. This depends on things like temperature, the amount of sunlight, and the availability of good food — milkweed for caterpillars and nectar-rich plants for adult monarchs.

Monarchs that emerge from their chrysalis in late summer or early fall have no choice but to migrate and overwinter. Because of this, part of their lifecycle gets delayed.They do not mature sexually before they migrate and do not breed during the winter. So their life span is six to nine months long — very different to the summer monarchs.

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Learning Objectives

Learn about the life-cycle of a butterfly

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Continue to M2. Monarch migration »