How Mosquitoes Become One with the Rain
June 5, 2012
For a tiny mosquito, being hit by a fat raindrop should be roughly equivalent to a person being slammed by a bus. However, mosquitoes are struck by raindrops all the time–and they usually survive. The secret of their success? They ride the raindrop, says mechanical engineer David Hu of the Georgia Institute of Technology in Atlanta. Why is this important? The mosquito’s low mass may explain how they are able to survive in rainy, humid climates. And it reveals why a rainstorm offers little or no protection against the pesky bloodsuckers. Engineers may also find the mosquito’s survival technique useful for designing tiny robotic flying machines that can operate under harsh weather conditions.
A female mosquito feeds from a person using her needlelike mouth parts. Her abdomen has become swollen with red blood. A female must drink blood to nourish her eggs. (© Dmitry Knorre, Dreamstime)
For their study, Hu and his team put mosquitoes in cages that vibrated so the insects wouldn’t be able to land. Then they bombarded the bugs with rainstorm-like waterdrops that were 50 times as heavy as the mosquitoes and came at them at a speed of 30 feet (9 meters) per second. High-speed videos of the blitz revealed that the flying mosquitoes simply stuck to the droplets. In the process, they absorbed only 10 percent of the force of the droplet. The maneuver is an insect version of t’ai chi ch’uan, Hu said, in which one minimizes the force of an attacking opponent by not resisting. In contrast, droplets falling on mosquitoes sitting on a twig crushed the bugs with a force equal to 10,000 times the mosquito’s weight.
The hitchhiking insects tumbled for a distance of up to about 20 times their body length before flying off. The bugs’ water-resistant hairs likely aid in their escape. But the scientists found that low-flying mosquitoes ran the risk of running out of escape room, with the raindrops becoming watery coffins.
