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The Western World Swallowtail butterfly flies far and wide with its impressive migration pattern. Thousands of miles — but they often travel over land, so they can stop to rest.
Scientists have found evidence that a group of winged travelers flew more than 2,600 miles (about 4,200 kilometers) across the Atlantic Ocean without stopping. New Research The findings were published in Nature Communications on June 25th.
The discovery brings to an end a decade-long mystery that began when entomologist and study lead author Dr Gerardo Talavera came across around 10 painted lady bugs, known by the scientific name Vanessa cardui, on a beach in Florida, US. French Guiana October 2013. The insect, which is not normally found in South America, had holes, tears and tattered wings.
“They looked exhausted. They could barely fly, and seemed to be hopping rather than flying,” said Talavera, a senior researcher at the Spanish National Research Council at the Barcelona Botanical Institute. “The only explanation that came to my mind was that these were migratory birds that travel long distances.”
But crossing an entire ocean was unprecedented, even for a land-dwelling butterfly like Painted Lady, and Talavera and his colleagues had to rule out several factors before concluding that these butterflies had accomplished something previously thought impossible.
Ann Survey conducted in October 2016 A paper co-authored by Talavera found that the painted lady migrates from Europe over long distances — about 2,500 miles — to sub-Saharan Africa, overcoming obstacles like the Mediterranean Sea and the Sahara Desert. But she still stays mostly on land, “where she can stop and refuel, eat flowers, and get the energy to migrate again,” Talavera said.
A new study suggests that it takes a painted lady butterfly five to eight days to cross the Atlantic, depending on a variety of factors.
Based on an analysis of energy constraints, the researchers concluded that the butterflies could fly up to about 485 miles (780 kilometers) without stopping, but favorable wind conditions allowed the butterflies to complete longer journeys, Talavera said.
“It’s actually a record for an insect, especially a butterfly, to fly such a long distance without the possibility of stopping,” said Talavera, who also leads the Worldwide Swallowtail Migration Project, a global citizen science project that tracks insect migration routes.
Talavera said there have been other cases where experts suspect butterflies and other migratory insects have traveled longer distances than normal and appeared on ships, islands and countries where they aren’t normally seen.
The researchers think the butterflies got lost when they were blown out to sea by winds on their annual migration south from Europe, he added, and then likely rode the trade winds out to sea. It blows from east to west near the equatoruntil they reached landmass in South America.
“It’s just incredible that they can hang in the air column at just the right height to take advantage of the trade winds,” says Dr. Floyd Shockley, collections manager in the entomology department at the Smithsonian’s National Museum of Natural History in Washington, D.C., who was not involved in the new study. “It raises the question: Have they been doing this for a long time and we just haven’t documented them in South America because we just haven’t been looking for them there?”
The occasional discovery of about 10 out-of-place butterflies, plus one that appeared to have been caught in a storm, may be enough evidence that this was a planned migration for this group of insects, Shockley said.
To determine whether the out-of-place butterfly had truly crossed the ocean, the researchers took several important steps.
First, to rule out the insects’ overland migration from North America, the researchers analyzed the insects’ DNA and found it matched that of European and African populations. Then, the team used a technique called isotope tracing, which uses the composition of the butterfly’s wings to infer the types of plants they ate as caterpillars, said co-author Megan Reich, PhD, a postdoctoral researcher at the University of Ottawa in Ontario. This method allowed the scientists to conclude that the butterfly originated from either Western Europe, North Africa, or West Africa, she added.
Gerardo Talavera
Using isotope tracing techniques, which examine the composition of butterfly wings to infer the types of plants they ate as caterpillars, the scientists concluded that the butterfly originated from either Western Europe, North Africa, or West Africa.
But the real key to finding the path the butterfly took is to first Survey conducted in September 2018 Dr. Talavera and his team found that pollen on the butterfly told the story of its migratory journey among the plants it feeds on. The butterfly, discovered in October 2013, was carrying pollen from two West African plants, Guiera senegalensis and Ziziphus spina-christi. The tropical shrubs flower from August to November, according to the study, and this flowering period matches the timeline of the butterflies Dr. Talavera found in South America.
What’s more, analysis of weather data from the 48 hours before the stranded butterflies were discovered showed that the times were “highly favorable for the butterflies to disperse across the Atlantic Ocean from West Africa,” the authors note in the study.
If the insect likely migrated from its native Europe to Africa and South America, the butterfly’s journey could have spanned more than 4,350 miles (7,000 kilometers).
“A lot of people think of butterflies as really fragile creatures, and this photo really shows how strong and tenacious they are and what an incredible journey they go on. They should never be underestimated,” Reich said.
The researchers hope to use the same technique to study the migration patterns of other butterfly species, she added.
“This is just the first step in a long process of trying to understand why this happened and how it happened,” Shockley said.
If future studies show that the butterfly migration is likely to follow a regular pattern, it would be one of the longest insect migrations in the world, he added.