Study Learns Why Flies Are So Hard To Swat

Fruit Fly In Flight

Flies are so tiny, with such eentsy-weentsy brains. So how can they, in just a few days of life experience, summon such masterful skills of elusiveness to avoid one human swatting onslaught after another?

The answer: years of evolutionary practice.

According to a study just published in Science magazine, flies employ tactical flying skills like banking, pitching and rolling that take the average aerospace engineer years of practice to become a veteran fighter pilot. Using high-speed video and intrusive winged robots dipped in mineral oil, researchers discovered that flies have genetically evolved “sensory-motor circuits that allow [them] to respond within a fraction of a second” with a banked turn to let them travel outside the range of threat.

“Based on the direction of the looming threat — whether from the back, the front or the side — the flies perform a different type of escape maneuver that is very controlled,” University of Washington researcher Florian Muijres told National Geographic.

Just by subtly changing the direction of the wings within a few flaps, flies are able to drastically change direction without altering velocity, the study found. Researchers envision this study leading to a better understanding of optimum maneuverability to allow the construction of robotic craft that can bob and weave around obstacles as astutely as our friends the flies.

Before this study, biologists believed flies avoided predatory threats by employing a yawing maneuver, which is similar to what a car’s driver feels during a turn, but high-speed video showed that flies instead relied on aerodynamic redirection instead (shown in the time-delayed video still below):

Fruit Fly Evasion in Motion

What startled scientists the most, said Oxford University professor Graham Taylor, was not the maneuver itself but the speed with which the flies performed it.

“The flies are responding to an approaching threat in half the time it takes to start blinking in response to a camera flash. And the time it then takes to accomplish the turn after that is even faster again, so they are throttling up to full power in a 50th of the time it takes you to complete that blink.”

Not only that: The study found that to survive the average swatting with this maneuver “the sensory recognition of an approaching threat (had to be) translated into evasive movement almost instantaneously.”

Fine. Now if only flies could figure out how to live longer than a month or so, under the best of conditions, they’d have us humans beat.

[Images courtesy of Florian Muijres/University of Washington]