Animals Wildlife Nature Blows My Mind! The Multi-Generation, 2,500 Mile Monarch Butterfly Migration By Jaymi Heimbuch Jaymi Heimbuch Twitter Writer California Polytechnic State University, San Luis Obispo Jaymi Heimbuch is a writer and photographer specializing in wildlife conservation. She is the author of The Ethiopian Wolf: Hope at the Edge of Extinction. Learn about our editorial process Updated August 13, 2020 credit: ajwazzer Share Twitter Pinterest Email Animals Wildlife Pets Animal Rights Endangered Species Every autumn, the largest migration of insects begins. Monarch butterflies are the only insect to travel thousands of miles from the cooler north to the warmth of southern regions to spend the winter. What may be most amazing about this migration is not just the distance, but the fact that it takes four generations of monarch butterflies to make the trip and that the butterflies -- four generations apart -- use the exact same trees to winter each year. By The Millions credit: Luna sin estrellas Monarch butterflies migrate by the millions. As many as 300 million monarchs will make the trip from northern areas of the continent to California and Mexico. Keeping Warm credit: aehack Most generations of monarch butterflies live anywhere from a few weeks to two months. However, the fourth generation born at the end of summer enters a phase called diapause, where they do not reproduce and can live for seven to eight months. It is this generation that lasts through the winter months in the south before the species begins the journey north as the weather warms in February or March. Stretching Their Wings credit: dave and rose The most popular places for monarch butterflies to spend the summer are in Mexico in oyamel fir trees, and near Pacific Grove, California where they live in eucalyptus trees. No one yet knows how the butterflies are able to find the exact same trees their ancestors used during hibernation. Multi-Generation Migration credit: Mike Baird In the spring when the migration north begins, the latest generation of monarchs will move north and east to lay eggs among milkweeds. This is the food source for the species' caterpillars. Young Caterpillars credit: Franco Folini It takes around two weeks for the caterpillar to grow before beginning the chrysalis phase. During this time, the caterpillar feeds on milkweed, and it is this diet that actually makes the mature butterfly foul-tasting and poisonous to predators. Chrysalis credit: puuikibeach After around 10 days in the chrysalis phase, the butterfly hatches from the cocoon. This begins the next generation of butterflies that will keep moving north during the summer months. Continuing the Journey credit: Mike Baird The second generation of monarchs is born during the early summer months of May and June, and the third is born during the height of summer in July and August. But it is the fourth generation born in September and October that makes the longer journey back south for the winter. Four generations for one annual migration. Amazing. Finding Sanctuary credit: Mike Baird The monarch butterfly is considered a near-threatened species because of their dependence on specific groves of trees for spending the winter months. As these trees are cut down, they lose the important habitat where they rest for winter. or as the trees nearby are cut down, the butterflies are exposed to the cold weather that can kill them. There are efforts underway to create more sanctuaries for migrating monarchs as well as to list them as a protected species.