Four Wings and a Prayer: Caught in the Mystery of the Monarch Butterfly

Every autumn, the monarch butterflies east of the Rockies migrate from as far north as Canada to Mexico. Memory is not their guide — no one butterfly makes the round trip — but each year somehow find their way to the same fifty acres of forest on the high slopes of Mexico’s Neovolcanic Mountains, and then make the return trip in the spring.

In Four Wings and a Prayer, Sue Halpern sets off on an adventure to delve into the secrets behind this extraordinary phenomenon. She visits scientists an...