Cabbage white butterflies are antisocial when they're laying their eggs. So if you stick up decoy butterflies, you can scare them off your crops. It's slightly oversize so it looks more intimidating to butterflies. Feel free to evolve the design.Printed Pesticide
Ignore butterflies attempting to mate with your decoy. They are stupid males and will not be laying eggs.
I write books. My latest is a YA science fiction novel called Homeland (it's the sequel to Little Brother). More books: Rapture of the Nerds (a novel, with Charlie Stross); With a Little Help (short stories); and The Great Big Beautiful Tomorrow (novella and nonfic). I speak all over the place and I tweet and tumble, too.