One of my favorite units when teaching first grade was the butterfly unit! Not only would we order Painted Lady caterpillers, but my students would also bring in caterpillars that they found in their gardens or in their neighborhoods. I never grew tired of watching the process of a caterpillar changing into a butterfly! I have a special fondness for the Monarch Butterfly and was excited when I saw this website:
http://www.learner.org/jnorth/monarch/ This site has an abundance of information about Monarchs! I highly recommend this site for your butterfly unit!