The world of a butterfly

The eastern black swallowtail butterfly, Papilo polyxenes, lays her egg on one of the plants her caterpillars can eat -- in this case, parsley. The larvae can also eat Queen Anne's lace, carrot greens, and fennel fronds.

Just before the larva (caterpillar) emerges, it is visible inside the egg.

The larva emerges from the egg about seven days after the egg was laid.

The first larval instar, or growth stage, looks nothing like the later stages. Early instars often look like bird droppings to fool predators.

At first the larva doesn't seem to move much, but within a few days, it has done visible damage to the parsley plant.

The second larval instar develops more complex markings as camoflauge.

Like all insects, butterfly and moth caterpillars have only six true legs -- visible here just behind the larva's head. The "prolegs" further back along its body aid in walking, but will disappear when the butterfly becomes an adult.

In the third larval instar, the caterpillar takes on its familiar black and pale green stripes and yellow spots.

Although many people think of a caterpillar changing into a butterfly all at once, its development is gradual. Here, the caterpillar's changing body structure can be seen.

Although we think of caterpillars changing into butterflies all at once, their development actually is gradual. Here, ten days out of the egg, the larva's changing structure can be seen.

As it grows, the larva is able to move easily from plant to plant in search of more food. It cannot go far, though, and so butterflies will lay their eggs only where there is enough food to support the caterpillar through its entire larval stage.

Thirteen days out of the egg, the larva is growing rapidly and needs a surprising amount of food.

All insects' bodies are divided into three parts: head, thorax, and abdomen. The larva's true legs, just behind the head, protrude from the thorax. All the sections behind it are part of the abdomen.

When the larva is threatened, it rears its head, and the red marking and yellow "horns" become more prominent.

Fourteen days after emerging from the egg, the larva leaves its bed of parsley in search of a place to pupate -- become a chrysalis.

The larva attaches itself by two threads to the underside of a leaf, stem, or branch, and forms a C shape.

Within hours, the larva has become a chrysalis. Inside this hard protective coating, the larva's body structures will be broken down and reformed into those of an adult butterfly. For the eastern black swallowtail, this metamorphosis will take 7 to 10 days, but some species take much longer.

Because the chrysalis is defenseless, it is often camoflauged to hide from predators. The eastern black swallowtail chrysalis may be green, grayish-brown, or combinations of those colors.

When metamorphosis is complete, the shell of the chrysalis becomes papery and translucent, and the adult butterfly can be seen inside.

After eight days, the adult butterfly emerges from the chrysalis. Its wings are wet, and it cannot fly until they dry.

The butterfly rests near its chrysalis while its wings dry. It is now visible to predators, and after weeks of growth and transformation, many adult butterflies are eaten before they can fly away.

After a few hours, the butterflies wings are dry. Soon it will fly away. Then, it will mate -- and begin the story again.