Spotty Mystery

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The beautiful wings of monarch butterflies are dotted with white spots, markings that have puzzled scientists for years.

Now, a research team set out to learn the role these white spots play in the insect’s flight, New Scientist reported.

Monarch butterflies are known for their impressive long-distance migrations: Despite weighing a little more than a raindrop, the alluring bug can in the fall fly nearly 2,500 miles from north to south to settle for winter hibernation.

Their black-and-orange wings are framed with a number of white spots. Some closely related species also have them, but they are not migratory and the spots are not very large.

For their paper, researcher Andy Davis and his team studied images of more than 400 monarch wings in different stages of the insect’s fall migration. They also analyzed monarch specimens from museums and compared them with six other closely related butterflies.

The findings showed that migratory monarch butterflies have bigger spots than their cousins. The team also observed that monarchs with just three percent more white markings on their wings were more successful migrants.

“We were pretty shocked at that,” said Davis.

Researchers suggested that the presence of white spots on the wings limits the absorption of sunlight and radiation. This difference in temperature between the light and dark areas of their wings could alter the airflow, reducing drag and enhancing their aerodynamics.

Still, their exact role remains a mystery and further investigation is required to confirm this hypothesis.

The authors proposed that spots appeared as the insects evolved to migrate longer distances compared with their predecessors.