What do fruit flies and fighter jets have in common?

Like fighter jets, fruit flies, too, can roll their bodies sideways to escape their enemies.

F. Muijres and F. van Breugel/University of Washington/REUTERS
A fruit fly, Drosophila hydei, flaps its wings 200 times a second during normal flight and even faster when taking evasive action.

If you have ever tried swatting a fruit fly, you will know how difficult it is.

While it is known that fruit flies are agile and quick to evade their enemies, a new study published in a paper titled "Flies Evade Looming Targets by Executing Rapid Visually Directed Banked Turns" in journal Science elevates their aerial agility to a whole new level.

When alarmed, tiny fruit flies respond like fighter jets by rolling their body at an angle of ninety degrees sideways, Florian Muijres, a University of Washington postdoctoral researcher and lead author of the paper told the Monitor.

“Although they have been described as swimming through the air, tiny flies actually roll their bodies just like aircraft in a banked turn to maneuver away from impending threats," said Michael Dickinson, a professor of biology at the University of Washington and a co-author of the paper in a press release. “We discovered that fruit flies alter course in less than one one-hundredth of a second, 50 times faster than we blink our eyes, and which is faster than we ever imagined.”

Using three high-speed cameras – each one capable of capturing 7,500 frames per second – researchers captured the motion of 92 fruit flies enclosed in a cylindrical drum.

The cameras had a shutter speed of one thirty-thousandth of a second. Therefore, it was essential that the arena be flooded with enough light so that the cameras could capture the flight motion of the flies. Very bright light could blind the flies and disorient their vision, so the researchers used infrared light instead. Neither humans nor fruit flies can see infrared light.

When a fly crossed the intersection of two infrared laser beams at the center of the drum, it generated an expanding shadow, which the flies interpreted as an impending threat.

The startled flies then turned at a speed five times faster than their normal speed. Researchers also observed that their evasive maneuvers were highly directed away from the direction of the stimuli, says Dr. Muijres.

And how do flies do that?

Apparently, the brain of a fly – which is as small as a salt grain – is the one which “performs a very sophisticated calculation, in a very short amount of time, to determine where the danger lies and exactly how to bank for the best escape, doing something different if the threat is to the side, straight ahead or behind,” Dr. Dickinson said.

The researchers intend to further explore how the fly’s brain and muscles carry out such maneuvers.

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