Scientists have long wondered how exactly the butterfly moves through the air the way it does.
It has long been believed that butterflies ‘flap’ their large wings to push forward, but scientists in Sweden have now determined that the movement is much more complex than previously thought.
Rather than just slaying them, they bend their colorful wings to create a ‘bag’ that traps more air and provides more propulsion.
That extra speed boost on takeoff can help the majestic lepidopterans avoid predators.
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Scientists in Sweden analyzed slow-motion video of a silver-washed mother of pearl in flight and found that the butterfly is not just flapping its wings. It forms a ‘pocket’ when they come together, which aids in propulsion
Butterflies are a tasty meal for a variety of animals, including frogs, spiders, lizards, and birds.
“If you are a butterfly that can take off faster than the others, you have a distinct advantage,” Per Henningsson, a biologist at Lund University, told the BBC.
“So it’s a strong selection pressure because it’s a matter of life and death,” he added.
In an analysis published in the journal Interface, Henningsson and fellow biologist Cristoffer Johansson showed that a butterfly’s “blow” propels a jet of air.
Researchers believe the extra thrust on takeoff could help butterflies avoid predators such as frogs and birds
They also found that it executes this movement “ in a much more sophisticated way than we ever realized, ” Henningsson told AFP.
The moment the wings slammed together, “it wasn’t just two flat planes slamming together.”
Instead, they form a ‘bag’ shape that traps more air.
Henningsson said it was not clear whether butterflies use the pocket technique in free flight, “but they certainly do a lot in the take-off phase.”
After watching a slow-motion video of the common silver-washed fritillary in flight, Henningsson and Johansson created two pairs of simple mechanical wings.
One set was rigid, the other flexible like real butterfly wings.
Mechanical wings as flexible as those of a butterfly were 28 percent more efficient and 22 percent better at generating power than rigid wings
The researchers found that the flexible wings were 28 percent more energy efficient – a “dramatic improvement” – and 22 percent better at generating power.
“While conventionally considered aerodynamically inefficient,” butterfly wings may be ideally suited to form the pocket shape, Henningsson said.
Their findings could be helpful in creating drones that use flapping wing propulsion, he added.
Last year, Cosmos reported that engineers at the University of South Australia have unveiled an ‘ornithopter’ the size of a bird, a flying machine that flaps its wings to generate forward thrust.
‘The people working on these designs … should be looking at this cup-shaped behavior since there [is] there is a lot of efficiency and effectiveness to be gained, ” Henningsson told the BBC.
The report could also help underline the importance of researching these wonderful bugs, which are seriously declining.
A new report from Butterflies Conservation Europe found that the UK’s butterfly population has fallen by half since 1976, with nearly one in ten British butterfly species extinct due to habitat destruction.
In California, the number of western monarch butterflies has plummeted to fewer than 2,000 butterflies from the tens of thousands counted in recent years and the millions reported in the 1980s.
Sarina Jepsen of the Xerces Society, which holds annual censuses of the California monarchs, told the AP “their absence this year was heartbreaking.”