Leonardo would approve.

Just as da Vinci looked at birds as inspiration for his sketches of airplanes about 500 years ago, engineer David Hu of the Georgia Institute of Technology is taking a close look at mosquitoes to understand how they can withstand the pounding of heavy rainfall.

This isn't just idle curiosity: Hu's research could help improve the design of insect-sized flying robots, which he says are being designed for use in military surveillance and search-and-rescue operations.

Hu is an assistant professor of mechanical engineering and biology at Georgia Tech in Atlanta. His research findings appeared in Monday's online edition of the Proceedings of the National Academy of Sciences.

His research looked at how mosquitoes, which often thrive in rainy, windy regions — and have done so for at least 170 million years — manage to survive impacts with raindrops during flight.

"These raindrops are moving at a very high speed of about 22 mph, which is too fast for mosquitoes to dodge while in flight," he says.

Though similar in size to mosquitoes, a single raindrop can weigh more than 50 times what a mosquito does. (In fact, a mosquito has the same ratio to a raindrop as a person would while trapped under the wheel of a car.)

Hu's team at Georgia Tech used high-speed cameras to film mosquitoes flying in a cage exposed to a water jet, which simulated rainfall. The study authors found that a mosquito's strong exoskeleton and low mass render it impervious to falling drops and help them survive collisions.

"The mosquito's low mass causes raindrops to lose little momentum upon impact and so impart correspondingly low forces to the mosquitoes," the authors write in the study. How low mass? A typical mosquito weighs about one-ten-thousandth of an ounce.

"If you were to scale up the impact to human size, we would not survive," says study co-author Andrew Dickerson, a doctoral student at Georgia Tech. "It would be like standing in the road and getting hit by a car."

Likening it to the principle of Tai Chi, where the idea is to allow an opponents' force to go through or around you, Hu says the mosquito and the raindrop fall together for about 20 body lengths, then release each other.

"They ride the drop, then reduce the force," Hu says.

All the mosquitoes in the study survived the collisions.

Though there had been many studies of insect flight, he says, this is the first study that looked at how mosquitoes interact with water using high-speed video cameras.

The study was funded by the National Science Foundation.

Mosquitoes are carriers of deadly diseases such as malaria, which kills hundreds of thousands of people each year around the world, according to the World Health Organization.

Hu's lab at Georgia Tech focuses partly on how animals and insects interact with water. A previous study looked at how fire ants survive flooding by grouping together as a raft, which can float effortlessly for days. Another looked at how dogs shake off water.