We do this every year because it is part of our science program. The school orders everything for us but I know that you can order from
www.insectlore.com. If you buy their butterfly house you get a certificate for free caterpillars. You can make your own butterfly house quite easily though. I did it last year because we had to return our cages to the company and we had baby caterpillars! There are two ways to do so. Let me know if you're interested and I'll give you the directions!