All butterfly and moth species begin life as caterpillars. Some caterpillars are quite vulnerable and rely on camouflage for protection, while others are armed with spines or bristles, or appear frightful to would-be predators. Some, like the woolly bear, are more well-known than their adult form. Because a caterpillar's job is to eat and grow, some of them are serious pests. All of them, if they survive, will transform into flying insects.

The caterpillar of the famous Monarch butterfly is attractive, with white, orange and black tiger stripes and two false antennae near its head and on its hindquarters. It eats milkweed and turns into a beautiful pale-green and gold-streaked chrysalis.

The caterpillar of the Isabella moth is so fuzzy that it’s been given the name woolly bear. Despite the legend, the black bands on its body don’t predict the severity of the winter. The common blue butterfly caterpillar, which occurs throughout North America, is a sluglike larva that feeds on dogwood flowers. It’s farmed by ants, who prize the honeydew it secretes. Being kept by ants might give the caterpillar some protection from predators.

The mourning cloak caterpillar eats the leaves of elm, willow and poplar trees. It’s full of bristles, as is the milkweed tiger moth. The mourning cloak is found in Canada; the tiger moth is found in the upper Midwestern United States. The caterpillar of the beautiful orange and yellow royal walnut moth is so frightful that it’s nicknamed the hickory horned devil. It’s green, with horns erupting from its head and its back. The caterpillar of the forest queen, found in tropical East Africa, has a caterpillar with a green head, four large black curved horns, eyespots and what looks to be a fish tail.

The caterpillar of the cabbage butterfly, found in most of the United States, is a serious pest on cabbage and other mustards. The eastern tent moth caterpillar spins tents in food plants like cherry trees, where they can strip whole branches of leaves.

The green caterpillar of the banded elfin butterfly is well camouflaged on its food plant of Virginia or pitch pine, as is the hackberry butterfly caterpillar. The caterpillar of the large maple spanworm, found in most of the United States, is brown and can stretch itself out so it resembles a twig. The caterpillar of the viceroy, found east of the Mississippi river, resembles bird droppings.