, Derry, New Hampshire

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June 6, 2012

Bad news: Raindrops don't swat down mosquitoes

Findings could aid design of tiny flying robots

A mosquito buzzes its way toward an open window, its unsuspecting victim sleeping peacefully in bed. Suddenly, a raindrop weighing about 50 times as much as the mosquito plummets straight down toward the insect. The drop should have the impact of a bus running over a human and drive the mosquito downward at a force up to 300 times that of gravity.

Sadly for the mosquito's next victim, the pest will survive this collision.

That's the conclusion of a team of engineers and biologists at the Georgia Institute of Technology in Atlanta, which used a combination of real-time video and sophisticated math to demonstrate that the light insect's rugged construction allows the mosquito to shrug off the onslaught of even the largest raindrop. The findings offer little aid in controlling the pest but could help engineers improve the design of tiny flying robots.

Aviation engineers know a lot about how rain impairs the flight of airplanes. Heavy rain increases drag, reduces lift, and increases the risk of stalling. But research on the impact of water on flying animals is sparse. One recent study on bats, led by biologist Christian Voigt of the Leibniz Institute for Zoo and Wildlife Research in Berlin, found that these furry fliers need about twice as much energy to power through the rain compared with dry conditions. Still, although some researchers have studied the dynamics of insect flight under a variety of conditions, scientists know very little about the effects of rain.

To help fill this knowledge gap, mechanical engineer David Hu and his colleagues at the Georgia Institute of Technology decided to subject Anopheles mosquitoes, the primary insect that infects people with malaria, to artificial rain conditions. Hu's team is already well-known for its studies of water-animal interactions, including the physics of how wet dogs dry themselves by shaking the water off.

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