National Geographic Readers: Great Migrations ButterfliesThe monarch butterfly, one of the most seemingly delicate of all of natures animals, proves to be one of the toughest in this reader. Making the yearly trip from the Northern United States and Canada to the Oyamel forest of Mexico is no easy task, and it takes five generations of butterflies in order to do so. Battling cold temperatures and the threat of starvation, these beautiful insects complete an almost 3,000 mile journey over the course of two