“When the wings go up during the upstroke, and they clap together at the end of the upstroke, we saw that they were not just two flat surfaces,” Henningsson explained.
“Instead they were bending, and due to their flexibility, (they were) forming a sort of pocket shape,” he said, adding that the team thought that in doing so, butterflies captured more air between their wings, which improved the clap and boosted performance.
The team tested the theory using a series of triangular robotic clappers and found that flexible wings increased the efficiency of the clap by 28% compared with rigid wings.
Experts think the creatures may have evolved to favor this unusual wing shape in order to evade predators.
“This flexibility might be one of the reasons they have this unusual wing shape,” Henningsson said. “Butterflies take off very quickly. They do this as a safety measure, to minimize risk of getting caught.”
The research was published Wednesday in the journal Interface.
Photos: The monarch butterfly
A monarch butterfly flies to Joe Pye weed, Wednesday, Aug. 28, 2019, in Freeport, Maine. The populations of both insect species have struggled in recent years. Rapid development and climate change are escalating the rates of species loss, according to a May United Nations report. (AP Photo/Robert F. Bukaty)
A monarch butterfly is buzzed by a bumblebee as it sips nectar on a Joe Pye weed, Wednesday, Aug. 28, 2019, in Freeport, Maine. The populations of both insect species have declined sharply in recent years. Rapid development and climate change are escalating the rates of species loss, according to a May United Nations report. (AP Photo/Robert F. Bukaty)
A fresh monarch butterfly wing is seen soon after it emerged in Washington, Sunday, June 2, 2019. Farming and other human development have eradicated state-size swaths of its native milkweed habitat, cutting the butterfly’s numbers by 90% over the last two decades. It is now under considered for listing under the Endangered Species Act. (AP Photo/Carolyn Kaster)
A fresh monarch butterfly wing is seen soon after it emerged in Washington, Sunday, June 2, 2019. Farming and other human development have eradicated state-size swaths of its native milkweed habitat, cutting the butterfly’s numbers by 90% over the last two decades. It is now under considered for listing under the Endangered Species Act. (AP Photo/Carolyn Kaster)
The monarch butterfly wing pattern is seen though its transparent chrysalis in Washington, Sunday, June 2, 2019. (AP Photo/Carolyn Kaster)
Laura Moore displays a newly emerged monarch butterfly on her finger in her Greenbelt, Md., yard, Friday, May 31, 2019. Despite efforts by Moore and countless other volunteers and organizations across the United States to grow milkweed, nurture caterpillars, and tag and count monarchs on the insects’ annual migrations up and down America, the butterfly is in trouble. (AP Photo/Carolyn Kaster)
This photo shows a monarch butterfly after it emerged in Washington, Sunday, June 2, 2019. (AP Photo/Carolyn Kaster)
A Monarch butterfly eats nectar from a swamp milkweed on the shore of Rock Lake in Pequot Lakes, Minn., Sunday, July 22, 2012. (AP Photo/Ann Heisenfelt)
A couple of Monarch butterflies mate at the Monarch Butterfly Biosphere Reserve, near the town of Chincua, Mexico, Thursday, Feb. 26, 2009. The Monarchs are not endangered, but scientists say deforestation could threaten its existence. (AP Photo / Marco Ugarte)
In this Jan. 4, 2015 photo, a swarm of Monarch butterflies fly between trees, in the Piedra Herrada sanctuary, near Valle de Bravo, Mexico. The population of the butterfly, that migrates thousands of miles each year from winter nesting grounds in Mexico, has been shrinking partly because farmers are growing more herbicide-resistant crops that have stripped millions of acres of milkweed they depend on to nourish them along their route. (AP Photo/Rebecca Blackwell)
Monarch butterflies fly in the Amanalco de Becerra sanctuary, on the mountains near the extinct Nevado de Toluca volcano, in Mexico, Thursday, Feb. 14, 2019. The Monarch butterflies arrive in central Mexico usually around the first week of November, after their yearly 4000-kilometer (some 2500 miles) migration from Canada and the United States, and begin their return around March. (AP Photo/ Marco Ugarte)
FILE – In this Feb. 14, 2019 file photo, a monarch butterfly rests on a man’s forehead at the Amanalco de Becerra sanctuary, in the mountains near the extinct Nevado de Toluca volcano in Mexico. Tree loss in the wintering grounds of the monarch butterfly in central Mexico is down by about 25% in 2019 compared to last year as a sharp drop in Illegal logging more than made up from an increase in tree deaths due to lack of water or disease, experts said Monday, Oct. 28, 2019. (AP Photo /Marco Ugarte, File)
Monarch butterflies cling to branches in their winter nesting grounds in El Rosario Sanctuary, near Ocampo, Michoacan state, Mexico, Friday, Jan. 31, 2020. (AP Photo/Rebecca Blackwell)
FILE – In this July 1, 2019, file photo, a monarch butterfly lands on a penta plant in the front yard of Tom Carroll and Hermine Ricketts in Miami Shores, Fla. Homeowners can attract butterflies to their gardens with a multitude of plants that include fennel, dill, and milkweed. (AP Photo/Wilfredo Lee, File)
A Monarch butterfly pauses in a field of Goldenrod at the Flight 93 National Memorial in Shanksville, Pa., Friday, Sept. 11, 2020. (AP Photo/Gene J. Puskar)
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