Since I've taught first grade I've done a butterfly unit in May. The kids really like it and each year I am able to add to the unit. We've done some great crafts, writing assignments, and I get to decorate my room with beautifully patterned butterflies. This year, thanks in part to Pinterest and discovering TpT, I'm adding even more. I'm expanding it to include insects in general at the beginning to gain background knowledge and gradually narrowing the topic to butterflies.
I got an iPad this year, a personal one not a school one. I do bring it in for lessons and other things. I was searching apps and I found an Insect Lore app that models ordering caterpillars from them. The app isn't too educational but it does provide good visuals for what will happen. You see them hatch from eggs,she'd their skin, make their chrysalis,emerge as a butterfly, and eventually free them. This happens in a very short amount of time. Also, you can't kill them if you forget about them for a few days.