This quick TED talk entry is courtesy of TED.com. Just like us, the monarch butterfly sometimes gets sick thanks to a nasty parasite. But biologist Jaap de Roode noticed something interesting about the butterflies he was studying — infected female butterflies would choose to lay their eggs on a specific kind of plant that helped their offspring avoid getting sick. How do they know to choose this plant? Think of it as “the other butterfly effect†— which could teach us to find new medicines for the treatment of human disease.