US Scientists Unlock Clues to Mystery of Butterfly Migration

Researchers find circadian clock in Monarch's antenna plays a major role in navigation

22 March 2010

Scientists believe antennas are critical to the navigation of the Monarch butterfly.

Deep in the forests of Michoacán, several hours drive north of Mexico City, tourists watch millions of Monarch butterflies as they cling to fir trees, gather on bushes, or take off in flight.

The striking black and orange insects winter in these mountains every year, traveling up to 4,800 kilometers to get here, from as far away as Canada. They stay through the winter, then, in the spring, the females leave these fir tree forests and head as far north as Kansas, to lay their eggs on milkweed plants.

It's an odyssey that inspires Chip Taylor, director of the Monarch Watch program in Lawrence, Kansas, over 2,000 kilometers north of the butterflies' winter habitat.

Earl RichardsonChip Taylor is director of the Monarch Watch program in Lawrence, Kansas.

"We see them usually between the 14th and 21st of April if they get this far north," he says, adding that many of them can barely fly after their journey. "A lot of those butterflies are so tattered and broken, that they're crawling from milkweed and milkweed to lay the eggs."

A journey guided by the senses

Just as remarkable as the distance they fly is how the butterflies navigate. After all, they don't have guides, or maps, or GPS equipment. Instead, they use sight, smell, touch and other senses to find their way. To study that, butterfly scientists track the insects' normal flight paths, then they confuse them and track their path again.