Butterflies are free -- and so are gypsy moths and cankerworms. From late spring to early fall you can gather eggs or larvae and nurture them through the fascinating process of metamorphosis, which small children can't quite believe is going to happen. After all, how could a furry little caterpillar change into a bright, winged butterfly?

"Any caterpillar that you find will hatch as long as you observe what it eats and provide that plant while it's in the larval stage," advised Sandy Burns, first-grade teacher at Capitol Hill Day School, who often takes her students on egg- and larvae-gathering trips. In a terrarium in the classroom were some tent caterpillars and some eggs that would turn into tent caterpillars and later into gypsy moths.

"Tomato hornworms are interesting because they pupate in the ground and turn into sphinx moths," added Burns. "In September we look for monarch butterfly larvae. They're found on milkweed, and you have to supply them with more milkweed to eat."

Jewel Stoddard, a former teacher and now co-owner of the Cheshire Cat Book Store on Connecticut Avenue, finds monarch eggs, which are pale green and cone-shaped, twice every summer.

"The first batch comes in late June and there's another batch in mid-August," said Stoddard. "You can find them wherever there's a lot of milkweed, in fields or meadows of along roadsides. The eggs are usually on the undersides of the leaves."

Stoddard hatches the August batch of monarch eggs in the bookstore window. The eggs hatch in three to five days, and the larvae are raised on milkweed. During the larval stage the caterpillars shed their skins several times.

"When I feel they're looking for a place to form their chrysalides, I put a big tree branch in the window," said Stoddard. "Depending on the weather, it takes three weeks to a month from eggs to butterflies. It's important to let the butterfliew dry their wings for about two hours before releasing them. If their wings are wet they won't be able to fly properly and birds might eat them. We usually have children take the butterflies out of the store and hold them on their hands until they fly away." b

If you don't want to do the gathering yourself, you can buy eggs or larvae from an insect supply source, which is how we got our painted lady butterfly larvae.

It started at Christmas, when we received a "Butterfly Garden" as a gift.

The garden was just a cardboard box with cellophane windows, but it came with a coupon for the larvae -- guaranteed to turn into butterflies. In February, we received in the mail a plastic container with five caterpillars crawling around on some brownish-green slime the accompanying folder described as their "nutrient." The trip may have been too much for the larvae, because in about a week it was obvious even to the most optimistic members of the family that they were dead. We took this demise philosophically, realizing that any butterflies that might have emerged would have frozen or starved in the flowerless Washington winter.

As the caterpillars were guaranteed to change into butterflies, we repacked the container with the remains in its original box to be sent back to the supply house. But we didn't send it back right away: Having gained some sensitivity to the needs of insects, we waited until spring.

The second container of caterpillars looked much like the first, but all of the larvae turned out to be healthy and they performed on schedule. During their second week with us, all of them crawled up and hung upside down from the top of the container. A few days later all of them had formed the translucent, iridescent chrysalides that meant they had entered the pupal stage. A chrysalis is less bulky and protective than a cocoon, which is what moths spin. That may explain why there are more moths than butterflies.

According to the instructions, while the old body parts of the caterpillar were changing into butterfly wings, we were supposed to be readying our Butterfly Garden. But it had been a long time since Christmas, and our Butterfly Garden had been either thrown away or trampled under little feet. Instead, we taped the container lid with the chrysalides hanging from it to the side of a tall plastic waste can and put a screen on top of it.

About a week later my daughter and a friend accidentally tipped over the substitute butterfly garden and noticed that the butterflies had emerged and were pumping their wings to dry them.

Called to the scene, I felt only momentarily like Prissy in "Gone With the Wind," then regained my composure, covered the wastebasket with a cloth and carried it outside.

Even after the screen was removed, the butterflies took a while to find their way to the top of the waste can. That gave us a chance to admire the markings of these specimens of Cynthia Cardui, the most widely distributed of all known butterflies. Two of them were mainly orange, yellow and black, while one was blue, orange and white. Before we could study their eyespots with a magnifying glass, they had flown out of the wastecan and were hovering low over out petunias and marigolds.

"I didn't even get to name them," complained my four-year-old.