Scientists using video cameras to track a fly's aerial maneuvers
found the insect employs astonishingly quick mid-air banked turns to
evade predators much like a fighter jet executes to elude an enemy.
Their study, published on Thursday in the journal Science, documents
aerial agility in fruit flies such as the capacity to begin to
change course in less than one one-hundredth of a second.
The fact that flies are airborne acrobats should not surprise anyone
who has ever swung a flyswatter at one, only to watch the little
insects easily escape.
The researchers at the University of Washington synchronized three
high-speed cameras operating at 7,500 frames a second to learn the
secrets of what the flies do to make themselves so elusive.
They tracked the mid-air wing and body motion of the fruit fly
species Drosophila hydei, which is about the size of a sesame seed,
inside a cylindrical flight chamber 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 upwards 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," he said.
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The fly flaps its wings about 200 times a second, and in almost a
single wing beat can reorient its body to maneuver away from the
threat and continue to accelerate, Florian Muijres, another of the
researchers, said in a statement.
"I suspect that these are very ancient reflexes," Dickinson added.
"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."
A lot of light was needed to accommodate the cameras'
extraordinarily high shutter speeds, but because a fly would be
blinded by the necessary amounts of normal light, the researchers
used very bright infrared lights. Like people, fruit flies do not
see infrared light.
"I've always been fascinated by flies. Everybody thinks that they
have a simple nervous system, but I think it's exactly the opposite.
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," Dickinson
(Reporting by Will Dunham; editing by Toni Reinhold)
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