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Nothing is quite so delicate and graceful as a butterfly in flight and, as new research shows, nothing is quite so aeronautically perfect.
Scientists at Oxford University in England have filmed free-flying butterflies for the first time, in a specially constructed flight tunnel, capturing the intricate, swirling patterns their wing beats make in wisps of smoke on high-speed digital photographs.
The pictures show what the wing beats of free-flying insects do to the air. Other visual studies have used tethered insects - moths, for example - glued to a lightweight rod. The red admiral butterflies, moving without restraint, show an extraordinary agility and complexity in their flight. Not only do they use many different wing strokes, they use them on successive wing beats.
"One insect uses all the known aerodynamic methods that anybody has conjectured," said Adrian Thomas, co-author of a report published on Thursday in the journal Nature.
Rather than progressing from one sort of wing stroke to another as flying speed changes - the way horses go from walk to trot to canter - the butterflies behaved more like Olympic gymnasts doing floor exercises, he said. If the average human being moved like the average red admiral, city footpaths would be filled with people progressing by hop, skip, jump, cartwheel and backflip, in no particular order.
Commenting in Nature on the research, Rafal Zbikowski from the Royal Military College of Science, in England's West Country, said the butterflies managed sophisticated manoeuvres with what is, by many standards, a minimal brain and neurological control system. "If engineers ever understand that," Dr Zbikowski wrote, "there will be a revolution in aeronautics."
The seemingly random flight patterns of red admirals, Dr Thomas said, may be intended to throw off predators. Less palatable butterflies, like monarchs, have more direct flights. Among the techniques used by the red admirals, Dr Thomas said, was a rotation of the wing at the end of a downward stroke, which creates a kind of backspin that produces lift in the same way as the movement of a sliced golf ball.
The butterflies also use what is called a clap and fling, The insect claps its wings together much like slamming a book closed, which pushes it away from the direction of the clap. Then by peeling the wings open, starting at the front, another rush of air is created that increases the force of the push.
The New York Times
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