Now, experts have found that insects “flap” their wings – and their wings have evolved perfectly for better propulsion.
Biologists at Lund University in Sweden began testing a 50-year-old theory that butterflies “flap” their wings together, pushing trapped air to create a jet and pushing 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, short, but very large wings in comparison to their small body,” Per Henningsson, associate professor of biology at Lund University, he told CNN. “This is a little complicated, because this type of wing is quite inefficient.”
Biologists studied free-flying butterflies and, in their aerodynamic analysis, found that the wings of the creatures are shaped like a shell during upward movement and “palms”, pushing the butterfly forward. Meanwhile, the downward movement helps with weight support.
They also noticed that the butterfly’s wings were behaving in an unusual way – instead of hitting each other, like two flat surfaces, the wings folded to create a “pocket shape” that would capture more air and improve propulsion.
“When the wings went up during the climb and clapped together at the end of the climb, we saw that there were just two flat surfaces,” explained Henningsson.
“Instead, they were bowing and, due to their flexibility, (were) forming a kind of pocket,” he said, adding that the team thought that in doing so, the butterflies captured more air between their wings, which improved clapping and performance boosted.
The team tested their theory using a series of triangular robotic appliques and found that the flexible wings increased the applause efficiency by 28% compared to rigid wings
Experts believe that the creatures may have evolved to favor this unusual wing shape in order to avoid predators.
“This flexibility may be one of the reasons why they have this unusual wing shape,” said Henningsson. “Butterflies take off very quickly – they do this as a safety measure, to minimize the risk of being caught,” he explained.
The research was published Wednesday in Interface magazine.