Despite their diminutive size, each monarch butterfly you observe flitting through your garden possesses the remarkable ability to embark on journeys spanning up to 4,000 kilometers (2,500 miles) each autumn. Recent research indicates that the white spots on their wings may play a crucial role in facilitating this extraordinary feat.
While it has long been known that the vibrant orange color of monarch butterflies (Danaus plexippus) serves as a warning to deter predators, the impact of wing colors on their migratory prowess had not been thoroughly explored until now, according to Andy Davis, an ecologist at the University of Georgia in Athens.
Monarch butterflies originate in Canada and the United States, where they breed, before embarking on a southward migration to spend the winter in either California or Mexico. Davis’s research team conducted an analysis of the wing colors of butterflies at the start of their migration and those that successfully completed the journey.
Contrary to their initial hypothesis, the researchers discovered that butterflies with less black on their wings were more successful migrants. Previous studies have revealed that black sections on animals, such as birds, aid in soaring. These black areas absorb light and heat the air above, reducing air resistance as the wing passes through.
However, Davis explains, “It turns out that we were wrong. It was the monarchs that had less black that actually were more successful at making it to the winter colonies.” These butterflies also had a greater proportion of white on their wings.
To further validate their findings, the team compared the wing colors of monarchs to those of related butterflies that do not migrate. The results revealed that monarchs possessed more white wing area, suggesting that the process of migration has driven the evolution of larger white spots. These findings were shared on June 21 in the journal PLoS ONE.
The precise mechanisms by which white wing spots enhance the monarchs’ ability to glide remain unclear. Areas of white on the wings absorb less sunlight and generate less heat in the air above them compared to darker areas. When these white and dark areas are adjacent, variations in air temperature can create swirling air currents. These currents may aid the butterflies in gliding, according to Davis.
To gain a deeper understanding of how wing colors influence butterfly motion, experiments conducted in wind tunnels may provide valuable insights. Additionally, this research could have practical applications in engineering. Davis suggests that by applying different colors, it might be possible to enhance the flight efficiency of drone technology.