WASHINGTON — Millions of Monarch butterflies migrate to Mexico for the winter, and scientists have long speculated on how the insects find their way. Turns out, their antennas are the key. Researchers painted butterfly antennas black, and the insects got lost.
Like most animals, Monarchs have a so-called circadian clock in their brain that helps them know what time it is. Knowing the time and the position of the sun allows them to orient to the south.
But Monarch butterflies have a second clock based in their antennas, which also sense light, according to the new study led by Dr. Steven M. Reppert, chairman of neurobiology at the University of Massachusetts Medical School.
“Whatever we learn about the insect . . . is going to tell us a little bit more about how our brain works,” said Reppert, who studies the clocks in the brains of animals and people.
Researchers had thought the navigation took place in the brain of the butterfly, but it turns out the brain and antenna each has a circadian clock and they work together, he said. The study appears today in the journal Science.
