Life Cycle of The Monarch Butterfly

Frostbite Theater presents... Cold Cuts! No baloney! Just science! Hi! I'm Joanna! And I'm Steve! And this is a field that used to house a bunch of ugly trailers that were used for office space. A couple of years ago the Lab tore them down and in an effort to cut the cost of lawn maintanence, they planted a bunch of wild flowers in their place. Last year Joanna and I planted this plant. This is milkweed. It's a plant that's native to Virginia and we planted it because it's the host plant for the Monarch butterfly. Monarchs spend their winter in Mexico and when Spring comes they fly north and search for milkweed where they lay their eggs. After about four or five days, if all goes well, the egg hatches and the larva, or caterpillar, emerges. The caterpillar has one job to do - eat! And it does this job very well. It spends the next two weeks or so eating as much milkweed as it possibly can. As it eats, it grows. It eventually becomes too large for it's skin, so it sheds its skin so it can grow some more. The times between sheddings are called instars and the Monarch larva goes through five of them. As the larva eats the milkweed it ingests toxins called cardiac glycosides. This makes Monarchs poisonous to most of the things that want to eat them, like birds. That's why the adults are brightly colored. It's a warning to potential predators to warn them to stay away. And, if one of them does get eaten, the thing that eats them learns really quickly to never eat a brightly colored butterfly again. That's why they need to lay their eggs on milkweed. They need the toxins to help protect themselves from other predators. After the larva has had its fill, it sheds its skin for the fifth and final time and enters the pupal stage. This is when the final metamorphosis into an adult butterfly occurs. After about a week to ten days, the chrysalis becomes transparent. That's the signal that the pupal stage is about to come to an end and the adult butterfly is getting ready to emerge. When the adult emerges it inflates its wings. Once its wings are dry, it flies off to find a mate so it can lay more eggs on more milkweed plants. It doesn't have a whole lot of time to do this, though. Most of the adults that emerge during the summer only live for two to five weeks. The adults that emerge in late summer and early fall are different. Instead of looking for a mate, they fly to Mexico where they spend the winter. After winter, they fly north and the whole cycle starts all over again. And that's the thing that's amazing to me. The butterflies that fly back to Mexico in the fall are the great, great grandchildren of the butterflies that flew from Mexico in the spring, and they fly back to the same mountain valleys year after year. And how they know where to go, and how to get there, is just completely beyond me. If you want to try this yourself, all you need to do is visit your local nursery and pick-up some milkweed. With any luck, you'll be able to follow the Monarch from egg to adult in your own garden! Thanks for watching! I hope you'll join us again soon! You know, this is a whole lot nicer than the trailers were. You know, it really is.