MADISON (WKOW) – This species of butterfly migrates twice a year, traveling about three thousand miles each time.
During the summer you may notice monarch butterflies, Danaus plexippus, flying from flower to flower while enjoying a meal. During this time of year, butterflies prepare to lay between 200 and 1,200 eggs on milkweed plants. A week after laying, if they survive, the caterpillars hatch and undergo five molts, growing each time.
After about 20 days, the caterpillar will become a chrysalis where it will spend another twenty days transforming from caterpillar to butterfly. As the caterpillar undergoes a complete transformation, one thing does not change: the ability to experience a semi-annual migration path.
Twice a year, in spring and fall, adult butterflies travel thousands of miles in one direction; in the fall, the butterflies move south to central Mexico. In the spring, butterflies travel north to the United States. While entomologists are still trying to figure out all the complexities, they do know a few things about this migration.
“These butterflies have specific clues that are just built into their DNA basically, they know these behaviors and they will use clues like orientation towards the sun to help them fly south,” says PJ Liesch, director of the laboratory. UW Madison Insect Diagnostic Unit.
But how adult butterflies transfer this migratory path to new caterpillars remains a mystery.
In the fall, during the months of September and November, these butterflies across the United States and southern Canada head south. Before that, these butterflies ate a lot and kept this food to help them feed throughout migration and hibernation.
By the time winter arrives in the United States, all butterflies will have reached central Mexico. Those who remain will most likely die from the cold. Insects that survived the migration will hibernate outside of Mexico City due to the near perfect climate to help them survive the winter months.
“It’s cool enough that they don’t burn calories, but it’s not too cold to freeze them. And they don’t want it to be too hot because they would be too active,” says Liesch.
The arrival of the monarchs is also around the time when Dia De Los Muertos, the Day of the Dead, begins in Mexico. It is believed that the monarchs were the souls of the returning dead.