Having a fruit fly buzzing around your head is fairly annoying, and ending up in a rage-induced swat-fest isn’t that unusual. Unfortunately, the fly always seems to be a few steps ahead of you and the swatting isn’t as successful as you’d like it to be. How do they manage to do it? According to a new study from researchers at the University of Washington led by Michael Dickinson, the flies have evasive maneuvers similar to a fighter jet. The results of the study were published in Science.
Fruit flies are incredibly fast. The species studied by the team, Drosophila hydei, are able to flap their wings at about 200 beats per second. Under ordinary circumstances, the fly just changes its heading in order to change direction. But when it is frightened, it is able to execute banked turns five times faster than it normally moves.
In order to study the fruit flies’ movements, 50 of them were put inside a drum and recorded with camera that captured them at 7500 frames per second (this means that the camera’s shutter opened and closed every thirty-thousandth of a second). Visible light bright enough to allow the camera to work would have blinded the flies, so the team had to use infrared, which the flies are unable to register.
Two laser lights were criss-crossed in the drum so when the fly flew through that light, it produced a dark shadow on the interior wall near it. The sudden appearance of the shadow startled the fly, causing it to go into a panicked hairpin U-turn.
In order to study the turn itself, the researchers reduced the film’s playback speed by 300x. A 3D computer model was created to allow the scientists to see additional details of the fly’s body positioning as it recognizes and responds to the stimulus. “We discovered that fruit flies alter course in less than one one-hundredth of a second, 50 times faster than we blink our eyes,” Dickinson explained in a press release, “which is faster than we ever imagined.”
“How can such a small brain generate so many remarkable behaviors? A fly with a brain the size of a salt grain has the behavioral repertoire nearly as complex as a much larger animal such as a mouse,” Dickinson continued. “That’s a super interesting problem from an engineering perspective.” The next step in this research will be to determine which parts of the brain control the muscles in order to execute this life-saving maneuver so quickly.
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