For a long time, I've been wanting to try one of the butterfly growing kits seen in educational toy stores. We finally decided this was the Summer to give it a try.
You buy the kit and send in a card to get your caterpillars delivered. You can even say the exact date you would like them to arrive. Then plop the catepillars in the little butterfly house and watch as they weave and wrap themselves in a cocoon. After about a week in their cocoons, the butterflies start to emerge.
I had my doubts but it really did work! It was an amazing summer science lesson that held everyone's interest for several weeks. Then it was time to release them outside. They flew away one by one, and the last one stopped and landed on a plant just long enough to wiggle his wings in goodbye!