A fly buzzes past your head and lands nearby; grab a flytrap or roll up a magazine and approach cautiously – and hit!
But no matter how fast you are, the fly is almost always faster and usually manages to avoid falling and escape unscathed. (Is he trying to annoy you ?!)
Flies have many adaptations that give them increased speed, maneuverability and perception, which makes them very, very good at detecting and avoiding even the fastest floats. And new evidence shows that modified rear wings of flies play an important role in launching them in a quick takeoff ̵
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Fly houses (Housefly) belong to the order Diptera, or true flies. Diptera have modified hind wings that have become small, rod-like structures with a button at the end called halteres. Their vibrations help insects stabilize their bodies while in flight by sensing body rotations and transmitting information to the wings.
Flies in the subgroup Diptera Calyptratae, which includes houseflies, also vibrate in their halters as they walk, but scientists don’t know why. In a study published online on January 13, 2021 in the journal Proceedings of the Royal Society B: Biological Sciences, researchers examined Calyptratae flies to see if careless oscillations affected their passage in the air, directing additional sensory data to coordinate movements in the muscles of the wings and legs.
Using high-speed cameras to capture tethered and laboratory-free flies during takeoff, the scientists recorded frames at speeds of up to 3,000 frames per second. They found that Calyptratae flies fired about five times faster than other flies; their takeoffs required an average of about 0.007 seconds (7 milliseconds) and only one wing strike.
“None of the Calyptratae have a take – off duration greater than 14 milliseconds [0.014 seconds], “the researchers said. By comparison, flies’ flights outside Calyptratae lasted about 0.039 seconds (39 milliseconds) and required about four wing strikes, according to the study.
The researchers then anesthetized the flies and removed the halters that all Diptera flies have. Calyptratae flies, which lack these lumps, took much longer to get up in the air, but the take-off time was not affected in flies that were not Calyptratae without halteres. Take-off stability also suffers when the halter is removed, but only in Calyptratae flies.
For example, Calyptratae insects, known as impact flies, which try to escape when taking off without their halters, “always lead to a crash on landing,” scientists said.
“This shows that Calyptratae flies need a halter for fast and stable take-offs,” said study lead author Alexandra Jarger, a doctoral researcher at Imperial College London. Jarger studied flies with the Fox Laboratory in the Department of Biology at Case Western University in Cleveland, Ohio.
The ability to escape predation is a big plus for an animal, and Calyptratae flies are extremely successful; with approximately 18,000 species described, they make up about 12% of Diptera’s diversity, Jarger told Live Science in an email.
“There will always be a trade-off between speed and stability when making an evacuation take-off, but Calyptratae seems to have found a way to undo some of the loss of stability by using their halters,” Jarger said. “Halteres allow Calyptratae to make faster and more stable escapes than many other species of flies.”
In the blink of an eye
Halters are not the only secret weapon in the fly’s evasive arsenal; once a fly is in the air, it can perform maneuvers that a fighter pilot would envy. Fruit flies can change course in less than 1/100 of a second – about 50 times faster than the eye can blink, Previously, Live Science reported. In experiments, the perfectly outlined wings of the wings generate enough force to quickly repel flies from a predator while in the air.
“These flies roll up to 90 degrees – some almost upside down – to maximize their power and escape,” said Florian Muires, who studied flight biomechanics at the University of Washington in Seattle and is now at the University and Wageningen Netherlands, told Live Science in 2014.
Flies also have an exceptional vision that helps them plan their jumps away from threats. About 200 milliseconds before takeoff, fruit flies use a visual warning of impending danger to correct their posture and indicate the direction that will take them to safety, the researchers wrote in 2008 in the journal Modern biology.
In fact, their improved perception juggles up to six times more visual input per second than humans can, the BBC reported in 2017
Animal brains perceive elapsed time by processing images at speeds known as “flicker fusion speed,” a term that describes how many images flash in their brains per second. Roger Hardy, an honorary professor of cell neurology at the University of Cambridge, England, implanted electrodes in the photoreceptors of flies’ eyes to measure their rate of flicker fusion, calculating it to be 400 times per second; the average rate of flicker synthesis in humans is about 60, according to the BBC. This means that the movement that you perceive as “normal” moves as a slow movement towards a fly.
With all these built-in benefits, it’s no wonder that the fly you’re trying to kill can escape. However, one approach that can improve your chances is to direct your blows to where the fly is likely to go, not where it rests, Michael Dickinson of the California Institute of Technology in Pasadena told The independent in 2011.
“It’s best not to move the fly’s starting position,” Dickinson said. “Head forward a little to predict where the fly will jump.”
Then again, you can just leave the fly alone, Jarger added. “They have just as much right to survive as any other animal,” she said.
EDITOR’S NOTE: The article was updated at 11:35 a.m. January 13 to January 13 to include quotes from the lead researcher and a video of experiments.
Originally published in Live Science.