Where do Monarchs go when they migrate?

When fall arrives, Monarch butterflies that have perched on Iowa trees, snacked on the state's flowers and fluttered across Eastern North America suddenly start to leave.

Something in the environment - temperature drops and other changes - tells all the Monarchs it's time to head south for the winter, according to the U.S. Forest Service. And so thousands of the black-and-orange winged butterflies start the long journey to the Sierra Madre Mountains of Mexico.

Researchers don't yet completely understand how the Monarchs all know where to go - butterflies have short life spans, so Monarchs only make the journey south once, and some Monarchs fly more than 3,000 miles to get to their new home. The earth's magnetic pull and the position of the sun are believed to help guide them.

The Monarchs we see in Iowa join other Monarchs that live east of the Rocky Mountains and fly together to the same dozen mountain areas of Mexico every year. They hang out in forests, clustering together to stay warm and dry until spring.

As spring melts the snow and warms the air, Monarchs lay their eggs, and new generations make their way back north. Monarchs are the only butterfly we know of that migrates this way - the same way birds fly south but later return.

While very few adult butterflies can survive the frosty Iowa winter, some do stick around. If you see a deep purple butterfly dancing in the snow, it might be a mourning cloak butterfly which, according to Iowa State University, weather the Midwestern temperatures until spring.

Comments: molly.duffy@thegazette.com