Butterflies Can Make Epic Journeys Across Atlantic Ocean, Shock Scientists: ScienceAlert

Some butterflies could cross entire oceans thanks to the wind.

A world-first study has just shown that the painted lady butterfly (Vanessa Cardui) can cross the world’s second largest ocean, the Atlantic, traveling 4,200 kilometers (2,610 miles) in just five to eight days.

This journey, the researchers say, “is one of the longest ever documented for an individual insect, 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 tired butterflies landed on the beaches of French Guiana with torn and tattered wings. Entomologist Gérard Talavera, who found the insects resting on the sand one October morning, was shocked.

They were painted butterflies, a common species with stable populations found on every continent except Antarctica and South America.

For years, Talavera wondered how these insects arrived in South America and where they came from. He finally has an answer.

By analyzing the DNA of pollen left on the butterflies, Talavera and his colleagues at the Botanical Institute of Barcelona showed that this lost flock probably arrived from sub-Saharan Africa, after undertaking an accidental transatlantic journey.

The adult insects appear to have been blown away by a strong trade wind in 2013 and carried 4,200 kilometres off course.

Judging by the trade winds that year, the journey would have taken the butterflies between five and eight days. With nowhere to land, the insects would have had to use their wings sparingly.

Without the help of powerful winds, researchers believe the herd would have traveled only about 480 miles before expending all its energy and perishing.

“Our results suggest that we may be underestimating transoceanic dispersal of insects and highlight the importance of air highways connecting continents via trade winds,” Talavera and colleagues write.

The monarch butterfly (Danaus plexippus) is world-renowned for its nearly 5,000-kilometer migration from North America to Mexico each year, but painted lady butterflies also undertake long-distance journeys between Europe and Africa each year. Some studies suggest that a single generation can migrate more than 4,000 kilometers.

That would make it the butterfly with the longest 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 like insects.

Isotopes have been discovered in the wings of the French Guiana painted butterflies, suggesting they were born in Western Europe. This means the flock may have travelled more than 7,000 kilometres in their lifetime, visiting no fewer than three continents.

“This is the first time that this combination of molecular techniques including isotopic geolocation and pollen metabarcoding has been tested on migratory insects,” explains geochemist Clément Bataille of the University of Ottawa in Canada.

“The results are very promising and transferable to many other species of migratory insects. This technique should fundamentally transform our understanding of insect migration.”

While the long-distance migration from Europe to Africa or from North America to Central America is undoubtedly impressive, there are also many places where butterflies can stop and refuel. An ocean crossing is a whole other challenge.

Painted ladies may only have wings the size of a pinky finger and brains the size of a pinhead, but they are incredible fliers.

In fact, their small size gives them an advantage: it allows them to glide with the winds, sometimes reaching speeds of 48 kilometers per hour.

It’s not just these humble insects that scientists underestimate.

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 travel quite a distance gliding on 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 incredible feats,” says entomologist Roger Vila of CSIC-Pompeu Fabra University in Spain.

“There is still much to be discovered about their capabilities.”

The study was published in Nature Communications.