For your unit on butterflies or moths, you will want to use the Teacher's Guide that is part of an Inquiry Box from the Florida Museum of Natural History. The guide has lessons, activities, coloring pages and diagrams to label.
Show your class these short clips of a butterfly making its chrysalis and watch as it hatches into a butterfly.
Rockingham County Public Schools has put together a great collection of science materials for your K-5 classroom, everything from PowerPoints to Interactive Whiteboard materials to video clips. Lots of butterfly resources included! (Note that as of Dec. 2014, the collection is no longer being maintained).