Even though a single raindrop can weigh 50 times more than a mosquito, the insect can still fly in the rain.
They found the mosquito's strong exoskeleton and low mass render it impervious to falling raindrops.
The research team, led by Assistant Professor of Mechanical Engineering David Hu and his doctoral student Andrew Dickerson, found that mosquitoes receive low impact forces from raindrops because the mass of mosquitoes causes raindrops to lose little momentum upon impact. To study how mosquitoes fly in the rain, the research team constructed a flight arena consisting of a small acrylic cage covered with mesh to contain the mosquitoes but permit entry of water drops.
They used a water jet to simulate rain stream velocity and observed six mosquitoes flying into the stream. All the mosquitoes survived the collision.
“The collision force must equal the resistance applied by the insect. Mosquitoes don't resist at all, but simply go with the flow,” Hu said. The team also filmed free-flying mosquitoes that were subjected to rain drops. They found that upon impact the mosquito is adhered to the front of the drop for up to 20 body lengths. “To survive, the mosquito must eventually separate from the front of the drop. The mosquito accomplishes this by using its long legs and wings, whose drag forces act to rotate the mosquito off the point of contact. This is necessary, otherwise the mosquito will be thrown into the ground at the speed of a falling raindrop,” Hu said.
The results of the research will appear in the latest issue of the Proceedings of the National Academy of Sciences.
