We did it last year when Katie was 4 1/2 and Andrew 2 1/2 and I think this year was even more fun! Both kids were so into checking the caterpillars to see if they turned into cocoons and then they anxiously waited for the cocoons to turn to butterflies. We had 5 Painted Lady butterflies!
The company we got them from is called Insect Lore. (www.insectlore.com). The caterpillars come in a small cup with a lid in the mail. Yep, in the mail. After about a week of so they get fatter and fatter and then hang from the lid and cocoon. 7-10 days later they turn into butterflies. You feed them sugar water and then release a few days later. Very simple. And very fun and educational!
Last year we released them on the bay in Ocean City, NJ. This year, at a butterfly sactuary park in Saratoga Springs, NY