A monarch butterfly perches on a branch in the Piedra Herrada sanctuary near Valle de Bravo, Mexico, last week.
A monarch butterfly perches on a branch in the Piedra Herrada sanctuary near Valle de Bravo, Mexico, last week. Christian Palma AP
A monarch butterfly perches on a branch in the Piedra Herrada sanctuary near Valle de Bravo, Mexico, last week. Christian Palma AP