Monarch Butterflies are stunning. And the annual migration of the Monarch butterfly is an incredible story. One researcher calls it “one of the most spectacular natural phenomena in the world”. (the following maps are from the USDA Forest Service) 
The eastern population of monarch butterflies migrates both north and south annually. But no individual makes the entire round trip; 3 to 4 generations are involved start to finish. Female monarchs lay eggs for the next generation during the northward migration. Every year they embark on a journey that takes them on a route as long as 4,800 miles from overwintering sites in central Mexico to southern Canada and the Northern United States.
Monarchs in Georgia
And check out the Journey North section of their site which gives additional migration information on Monarchs as well as other wildlife like Hummingbirds, Bald Eagles and songbirds including American Robins.
This table from MonarchWatch.org gives approximate dates by latitude for the fall migration south so you can see when they will be passing through Georgia (the latitude for Atlanta is 32° North)
Milkweed’s Importance to Monarchs
Monarchs will only lay their eggs on milkweed plants since the newly hatched caterpillars will eat only the leaves of this plant. For any number of reasons, humans have eliminated much of the milkweed populations in the U.S. That, combined with habitat reduction in their overwintering site in Mexico, has pushed the spectacular Monarch migration close to extinction.  The good news: gardeners across the country are helping by planting milkweed! (More on that below.)
As a result of the caterpillars’ feasting on milkweed plants the monarch is loaded with toxic substances known as cardiac glycosides acquired from the plant. These substances render it unpalatable to many of its predators, and its brightly colored wings serve as a warning sign of its toxicity. 
Mimics and Look Alikes
The Viceroy butterfly mimics the Monarch to take advantage of the fact that predators have learned the Monarch is toxic. Take a look at the side-by side comparison of the Monarch and Viceroy below:
In addition to the Viceroy, two other Georgia butterflies can be mistaken for the Monarch: the Gulf Fritillary and the Queen Butterfly. We have a comparison page with all four shown together to help with identification.
We were able to capture this video of two monarchs mating at Harris Neck National Wildlife Refuge near Darien, Georgia in September, 2014. Both butterflies look a little tattered, but are mating nonetheless. The female will need to find milkweed on which to lay her eggs.
Life Cycle 
The caterpillar goes through five growth stages. At each stage the instar molts to become bigger all the while storing energy to make it through the chrysalis stage.
In the pupa or chrysalis stage, the caterpillar spins a silk pad on a horizontal surface and then hangs upside down, resembling the letter ‘J’. It sheds its skin, and becomes encased in a gorgeous, jewel-like exoskeleton. During this pupal stage, the adult butterfly forms inside. The exoskeleton becomes transparent before it emerges, revealing the vivid monarch colors.
An adult butterfly emerges after about two weeks and initially hangs upside down until its wings are dry. It then pumps fluids into the wings, and they expand and stiffen at last enabling flight in search of nectar plants and a mate.
Take a look at this cool time lapse video:
How can you help?
- Plant their host: native milkweed. It is the only plant the caterpillars eat.
- Plant flowering plants that provide nectar and energy for the adult butterflies.
- Stop using pesticides.
- Spread the word. Pockets of milkweed in urban gardens have a powerful impact and help to save this migration.
- Want to do more? Certify your yard as a Monarch waystation at Monarchs Across Georgia or MonarchWatch.org and join the fun!
References and Additional Information
 Learner.Org: Journey North
 USDA Department of Agriculture Forest Service: The Monarch Butterfly in North America
 USDA Department of Agriculture Forest Service: Monarchs – Migration and Overwintering
 Monarchs Across Georgia: Pollinator Habitat
 Monarch Watch: Peak Migration Dates (Atlanta’s latitude is 32)
 Monarch Watch: Monarch Waystation Program
 Xerces: Monarch Butterflies in North America Found to be Vulnerable to Extinction
 The Washington Post: The monarch massacre: Nearly a billion butterflies have vanished
 National Wildlife Federation: Monarch Butterfly
 Ladybird Johnson Wildflower Center: Asclepias tuberosa (Butterflyweed)
 Dunwoody Nature Center: The Milkweed Project
 Encyclopedia Britannica: Mutual Mimicry: Viceroy and Monarch
 Wikipedia: Monarch Butterfly