My family has some pets you might think of as unusual.

We have a tank of Eastern Black Swallowtail caterpillars. We found the eggs in our garden. Swallowtails lay their eggs on plants in the carrot family (including fennel, dill, Queen Anne's lace and parsley). The eggs are white and the size of a pinhead.

When they are about to hatch, they get darker. When the eggs hatch, the caterpillars are really tiny -- about a millimeter long. They eat like crazy for about 10 days until they are full grown (1 1/2 to 2 inches). This is my favorite stage because they are big enough to pet and you can see all their beautiful markings clearly. Their bodies are green with yellow and black markings.

Soon the caterpillars get really restless and they start looking for a safe place to make a chrysalis. When they are ready, they attach themselves to the surface with little silk threads. In our tank, they like to use the sticks we put in for them or the side of the glass. Some pupae are green and some are brown. It is good camouflage because if the caterpillar makes a pupa on a rough surface like a twig, it is usually brown. If it is on something smooth like a live plant (or the aquarium glass), it is usually green.

In about two weeks, something very exciting happens. Out comes a butterfly! It looks a bit odd at first. All of its blood is still in its body. It pumps up its wings and then it is ready to fly away.

Just don't forget to sing "Happy Birthday" before you let it go.