Some butterflies may be able to travel across entire oceans with the help of the wind.
A world first study has now shown that the painted lady butterfly (Vanessa Cardui) can cross the world’s second largest ocean, the Atlantic, covering 4,200 kilometers (2,610 miles) in just five to eight days.
The journey, the researchers claim, “is among the longest documented for individual insects and potentially the first verified transatlantic crossing”.
The incredible discovery was made after more than a decade of mystery.
It all started in 2013, when a flock of exhausted butterflies landed on the beaches of French Guiana with their wings torn and torn apart. Entomologist Gerard Talavera, who found the insects resting in the sand early on an October morning, was shocked.
These were painted lady butterflies – a common species with stable populations found on every continent except Antarctica and South America.
For years, Talavera was left wondering: how did insects get to South America and where did they come from? Finally he has an answer.
By analyzing the DNA of the pollen left in the butterflies, Talavera and his colleagues at the Botanical Institute of Barcelona have shown that this lost flock may have flown in from sub-Saharan Africa after making an accidental transatlantic journey.
It appears that the adult insects were caught in a strong trade wind in 2013 and blown 4,200 kilometers off course.
Judging by the trade winds that year, the trip would have taken the butterflies about five to eight days. With nowhere to land, insects would have to use their wings sparingly.
Without the help of powerful winds, the researchers theorize that the flock would have only traveled about 480 miles (780 kilometers) before using up all their energy and dying.
“Our findings suggest that we may be underestimating transoceanic dispersal in insects and highlight the importance of the trade wind air highways connecting the continents,” Talavera and his colleagues write.
Monarch Butterfly (Danaus plexippus) is world famous for its nearly 5,000-kilometer-long migration that it makes each year from North America to Mexico, but painted lady butterflies also make long-distance journeys between Europe and Africa every year. Some studies suggest that a single herd can migrate more than 4,000 kilometers.
This would make it the butterfly with the longest lifetime migration, but unlike other animals that travel through the air, such as birds, it is much more difficult to track the global movements of small creatures such as insects.
The wings of painted lady butterflies in French Guiana were found to contain isotopes suggesting they originated in Western Europe. This means the herd may have traveled more than 7,000 kilometers in a lifetime, visiting no fewer than three continents.
“It is the first time that this combination of molecular techniques, including isotope geolocation and pollen metabarcoding, has been tested in migratory insects,” says geochemist Clément Bataille from the University of Ottawa in Canada.
“The results are very promising and transferable to many other migratory insect species. The technique should fundamentally transform our understanding of insect migration.”
While the long-distance migration from Europe to Africa or North America to Central America is certainly impressive, there are also plenty of places for butterflies to stop in between and refuel. An ocean crossing is a completely different challenge.
Painted ladies may only have wings the size of a pinky finger and a brain the size of a pinhead, but they are incredible flyers.
In fact, their small size gives them an advantage. This allows the species to glide in winds, sometimes traveling at speeds of up to 48 kilometers (30 miles) per hour.
It’s not just these lowly insects that scientists are underestimating.
Winds blowing across the Atlantic from the Sahara to the tropical Caribbean are also stronger than experts once thought, capable of carrying large dust particles up to 3,500 kilometers.
It makes sense that a small winged creature could make it glide far in these winds with minimal flapping effort.
“We usually see butterflies as symbols of the fragility of beauty, but science shows us that they can perform extraordinary feats,” says entomologist Roger Vila of CSIC-Pompeu Fabra University in Spain.
“There is still much to discover about their abilities.”
The study was published in Nature Communications.