This larval stage usually lasts from two weeks to about a month. This is the main feeding stage of the butterfly. Caterpillars eat almost constantly and grow very quickly, at an astonishing rate.

Diet
Caterpillars mostly eat the leaves of flowering plants and trees using their powerful jaws (mandibles) Caterpillars are very limited in their diet; many species will only eat the leaves of a single type of plant. They usually eat only the plant that their mother carefully chose to lay their egg on.

Only a few lepidoptera larva are carnivores. The larva of the Harvester Butterfly exclusively eats woolly aphids.

Growing and Molting
As caterpillars grow, their exoskeleton becomes tight on them, so they molt (lose their old exoskeleton). After the molt, while the new skin is still soft, they swallow a lot of air, which expands their body. Then, when the cuticle hardens, they let the air out and have room for growth.

The Tiger Swallowtail caterpillar has large eyespots that make it look like a large snake-like predator and not a vulnerable larva.

Caterpillars molt four or five times as they grow. Each different caterpillar stage is called an instar.

Preparing to Pupate
When larval growth is done, the larva stops eating and empties its digestive system (leaving a small dark spot). It then looks for a sheltered, safe spot where it will pupate (turn into a pupa, entering its third stage of its metamorphosis).

When the caterpillar has reached the right size, it is time for it to pupate. It finds a suitable place to attach itself (a twig, a leaf, undergroud, or another place). It attaches itself with a silken girdle around its middle and a silken pad and cremaster (at the end of the abdomen). It then splits open and loses its exoskeleton and pupates (becomes a pupa).

More on Caterpillars
To learn about caterpillar anatomy, click here.

Caterpillar Anatomy Printout

Simple Caterpillar printout.