How minuscule mosquitoes survive blows with huge raindrops
Mosquitoes are drawn to humid climates, as anyone who lives near a creek or swamp knows, but scientists have long wondered how the tiny critters avoid what should be deadly collisions with raindrops 50 times their weight.
During a rainstorm, it's likely that mosquitoes get hit about every 25 seconds, reports Ars Technica, and they don't weave in and out of raindrops. So how do they survive?
Researchers have found that a mosquito's low body weight (and size) and hard exoskeleton help it take on the impact of a raindrops mid-flight without much harm.
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In this video, David Hu, a Georgia Tech biologist, and his colleagues set up an acrylic cage and high-speed cameras to film exactly how mosquitoes get around in stormy weather. To simulate raindrops, which move at a rate of 9 yards per second, they tried dripping water off the third floor of a building into the cage at ground level. But, he told Science News, "It's the worst game of darts you can imagine. You have no hope of hitting them." So they began spraying water from a jet.
Most of a mosquito is made up of legs and wings, which can take small hits from a water droplet without changing the bug's flight path much. As you can see, when the mosquitoes are hit by a falling raindrop, their flight is only interrupted slightly as they turn or spin to avoid the collision.
But if the water hits the bug's body, it will take on the speed of the water droplet. This acceleration in the rate of flight happens extremely quickly, and is now the fastest known acceleration done by any insect. Their bodies are so small, in fact, that the water droplet doesn't break over them, but glances off the bug's back without much force transferred to the insect.
"There's something special about being very lightweight," Hu said.
A mathematical model supported the notion that the lighter the object, the less force a water droplet exerted on it: an airborne mosquito struck by a raindrop feels a force equivalent to the weight of a feather, reports Discovery Magazine. But a bug on the ground would most certainly take a harder hit.
If the drops hit the body of the bug while it's mid-flight, they engulfed the mosquitoes, who tumbled head over wings toward the floor with the water. But after the drop has traveled about 13 body lengths, the hairs on the mosquito's body and legs allow it to break free and fly toward the wall, showing no signs of harm.
"The drop comes at the speed of a comet, and instead of the mosquito resisting the force applied by the drop, it basically gets adhered to the drop like a stowaway," Hu told LiveScience.
The team said the insects survive because their hardened exoskeletons allow them to carry heavy loads. Though, if they're near the ground when they get hit, they'll definitely go splat before they can escape the drop's pull.
"It's well known that these insects are robust. They basically can survive any kind of wind and most weather conditions," Hu said. "We want to understand what body adaptations do they have to survive these kinds of things and how can that be used for engineering?"
With more and more drones being created the size of insects, this kind of knowledge could come in handy for robotics engineers creating micro-airborne vehicles.
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