We purchased a bushel of corn from a shack near a farm. As advertised, the organically-grown pesticide-free corn really had bugs in them. One of these bugs was a really plump green caterpillar, and we decided to save it.
It was a great opportunity for the boys to learn about these critters, and Wikipedia is an excellent place to start. We learned that caterpillars have about 4,000 muscles (humans have 629) with 248 muscles in the head segment alone!
We prepared a jar with some extra food, including corn silk and husks. Now, we're watching and waiting...