WASHINGTON – The fact that flies are airborne acrobats should not surprise anyone who has ever swung a flyswatter at one, but scientists using video cameras to track a fly’s aerial maneuvers found they employ astonishingly quick midair banked turns to evade predators much like a fighter jet executes to elude an enemy.
Their study, published Thursday in the journal Science, documents aerial agility in fruit flies such as the capacity to begin to change course in less than a hundredth of a second.
The researchers at the University of Washington synchronized three high-speed cameras operating at 7,500 frames per second to learn how the flies make themselves so elusive. They tracked the midair wing and body motions of the fruit fly species Drosophila hydei, which is about the size of a sesame seed, after the insects were shown an image that suggested an approaching predator.
The flies produced impressive escape responses, almost instantaneously rolling their bodies like a military jet in a banked turn to steer away. While executing the turn, the flies showed that they could roll on their sides by upward of 90 degrees, sometimes flying almost upside down.
“They generate a rather precise banked turn, just like an aircraft pilot would, to roll the body and generate a force to take them away from the threat,” said University of Washington biology professor Michael Dickinson, who led the study. “That happens very quickly. And it’s generated with remarkably subtle changes in wing motion. We were pretty astonished by how little they have to do with their wing motion to generate these very precise maneuvers.”
The fly flaps its wings about 200 times a second, and in almost a single wing beat can reorient its body to escape the threat and continue to accelerate, said Florian Muijres, another of the researchers.
“I suspect that these are very ancient reflexes,” Dickinson explained. “Very shortly after insects evolved flight, other insects evolved flight to eat them. Circuits for detecting predators are very, very ancient. But this one is just being implemented in a high-performance flight machine.
“Everybody thinks that they (flies) have a simple nervous system, but I think it’s exactly the opposite,” he added, “they just have a really tiny one. But it’s incredibly compact. They do so much with just this brain the size of a salt grain.”
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