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New Clues to Migration

Millions of monarch butterflies migrate from the United States to Mexico each winter. But how do they find their way over the thousands of miles? Their antennas are a key, according to a new study in the journal Science.

Monarchs, like people, have an internal "clock" that helps them keep track of time. The study shows that monarchs also use their antennas to sense light. Knowing the time and the position of the sun allows them to head south and stay on course.

Researchers tested butterflies by dipping their antennas in paint. Butterflies whose antennas were removed or coated with black paint got lost. But butterflies whose antennas were coated with clear paint, which didn't affect the antennas, had no trouble navigating.

"Whatever we learn about the insect...is going to tell us a little bit more about how our brain works," said Steven M. Reppert, who led the study.

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