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How does a tiny insect migrate thousands of miles from Canada to Mexico each year? What does the decline of monarch butterflies tell us about the ecological health of our continent? How are scientists using gene editing to understand how insects have evolved to tolerate poisonous plants? Anurag Agrawal is a biologist at Cornell University who studies plant-insect interactions, including monarch butterflies. He is the author of a new book called "Monarchs and Milkweed: A Migrating Butterfly, a Poisonous Plant, and Their Remarkable Story of Coevolution.” On this episode, Art and Marty talk with Anurag about the incredible migration of the monarch butterfly, the recent decline in population and a fascinating study where scientists edited the genomes of fruit flies to make them resistant to a poisonous plant that monarchs eat.