The Caterpillar (The Butterfly Life Cycle)

Spicebush Swallowtail (Papilio troilus) larva
Spicebush Swallowtail (Papilio troilus) larva

The caterpillar is the larval stage in the butterfly life cycle.

After the egg hatches, it may start its eating binge by eating the shell of the egg from which it hatched. Most butterfly larva will eat the host plant its egg was laid on. Some eat flower buds, seeds or roots.

A larva is often well camouflaged in shades of greens and browns. Some look like bird droppings. Others like the milkweed larva, are brightly colored to warn off those who would eat it. The milkweed larva tastes bad. It gets this bad taste from eating the milkweed plant, its host plant. The photo is of Milkweed butterfly larva on a milkweed pod. Other larva are covered with spines, false eye spots and other markings.

Pipevine Swallowtail (Battus philenor) larva on Dutchman's Pipe
Pipevine Swallowtail (Battus philenor) larva on Dutchman’s Pipe

Most larva eat alone. But some eat in groups

It alternates periods of feeding and resting during the day.

If it survives predators and disease long enough, it will grow to a mature larva. In this larval stage it’s skin is still soft. Is is vulnerable to parasites that try to lay their eggs within the caterpillars. These parasites would then hatch and eat it.

Caterpillars may grow for two to four weeks. It accumulates enough fat to go through metamorphosis and change into a butterfly. It’s skin will only stretch a small amount. When it can no longer stretch anymore it grows a new skin. It will molt or shed it’s skin four to six times during the larval growing stage. It sheds its old skin starting with the head. After shrugging off the old skin, it will expand its body with air to get rid of the old skin before the new skin hardens. The new skin is soft and moist.

Black Swallowtail (Papilio polyxenes) caterpillar on flat leaf parsley.
Black Swallowtail (Papilio polyxenes) caterpillar on flat leaf parsley.

Once it reaches the full size, it stops eating. It will look very swollen. It will stop moving and stay very  still. It may wag the front part of its body from side to side and may wander away from the food plant.

Monarch butterfly larva preparing to become a chrysalis
Monarch butterfly larva preparing to become a chrysalis

It then looks for a place to pupate. If it will change while hanging from a plant, it spins a silken pad with its lower lip or jaw spinnerets. This silken pad anchors it to the plant. The caterpillar hooks to the silk pad with its rear claspers. It hangs upside down from the pad. Others species spin a silken harness to secure it to the plant.

If it is close to winter, the caterpillar may crawl into leaf litter, a log pile or other sheltered spot. The chrysalis may turn brown to better camouflage in the brown of the log or leaf litter.

It may stay still for about a day, as the pupal skin forms under the old skin. It molts one last time into a pupa or chrysalis.

The metamorphosis from caterpillar to chrysalis is the next stage in the butterfly life cycle.

Swallowtail chrysalis
Swallowtail chrysalis

Monday’s post: The chrysalis stage of the butterfly life cycle.

One comment

  1. Thanks so much for taking us through the changes, Donna. I knew all this well when I was child, but had forgotten the details. Look forward to the next stage.

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