If you've never read Ray Bradbury's short story, A Sound of Thunder, you definitely should. It tells a haunting story about how past acts effect the future. A butterfly plays a key role.
I was reminded of this story when I was walking to my car in the Trader Joe's parking lot and came across two butterflies resting in the middle of the asphalt. It's a miracle they weren't run over by all the parking cars. I picked each one up and brought it to the wood chips along the building. I hope I did my part for the future.