Now, experts have found that insects “clap” their wings together – and that their wings are fully developed for better propulsion.
Biologists from Sweden’s Lund University set out to test a 50-year-old theory that butterflies “clap” their wings together, pushing trapped air out to form a jet and propel the animal in the opposite direction.
“Butterflies look different from many other flying animals, compared to birds and bats. They have a very extreme wing shape – wings that are very large and short but very wide compared to their small body,” Per Henningson, assistant professor of biology at Lund University, told CNN. “That’s kind of a puzzle, because this type of suite is not functional at all.”
Biologists studied freely flying butterflies, and in their aerodynamic analysis, they found that the creatures’ wings form a concave shape during stroke and “flutter”, which pushes the butterfly forward. Meanwhile, stroke helps support weight.
They also noticed that the butterfly’s wings were behaving in an unusual way – instead of colliding with each other, as the two surfaces were flat, the wings were bent to create a “pocket shape”, which would capture more air and improve propulsion.
“When the wings rise during the stroke, and clap together at the end of the stroke, we saw that they are not just two flat surfaces,” Henningson explained.
“Instead they were bending, and because of their flexibility, (they) were forming a kind of pocket shape,” he said, adding that the team believed that by doing this, the butterflies captured more air between their wings, which improved the clap and enhanced performance.
The team tested their theory using a series of triangular mechanical clappers, and found that the flexible wings increase Clap efficiency of 28% compared to hard wings
Experts believe the creatures have evolved to prefer this unusual wing shape in order to avoid predators.
“This flexibility may be one of the reasons why they have such an unusual shape on the wing,” Henningson said. “The butterflies take off very quickly – they do this as a safety measure to reduce the risk of being captured,” he explained.
The research was published Wednesday in the journal Interface.