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Now, experts have found that the insects “flap” their wings together – and their wings are perfectly evolved for better propulsion.
Biologists at the Swedish University of Lund set out to test a 50-year-old theory that butterflies “flap” their wings together, pushing the trapped air to create a jet and push the animal in the opposite direction.
“Butterflies are different from many other flying animals, compared to birds and bats. They have a very extreme wing shape – very large wings, short but very wide compared to their small body,” Per Henningsson, associate professor of biology at Lund University, told CNN. “It’s a bit of a puzzle because this type of wing is quite inefficient.”
Biologists have studied free-flying butterflies and, in their aerodynamic analysis, found that the creatures’ wings form a cross-sectional shape during the ascent and “snap”, pushing the butterfly forward. During this time, the downward stroke helps support the weight.
They also noticed that the butterfly’s wings behaved in an unusual way – instead of snapping together, like two flat surfaces, the wings bent to create a “pocket shape,” which would capture more air and improve propulsion.
“When the wings go up during the upstroke, and they click together at the end of the upstroke, we saw that they weren’t just two flat surfaces,” Henningsson explained.
“Instead, they curved and, due to their flexibility, (they formed) a sort of pocket shape,” he said, adding that the team believed that in doing so the butterflies captured more. of air between their wings, which improved clapperboard and improved performance.
The team tested their theory using a series of triangular robotic flaps and found that the flexible wings increased the 28% clap efficiency compared to rigid wings
Experts believe the creatures may have evolved to favor this unusual wing shape in order to evade predators.
“This flexibility could be one of the reasons they have this unusual wing shape,” Henningsson said. “Butterflies take off very quickly – they do it as a safety measure, to minimize the risk of getting caught,” he explained.
The research was published Wednesday in the journal Interface.
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