How military might benefit from study of hard-to-kill mosquitoes

Did you ever wonder what happens to mosquitoes caught in a rainstorm? If a big, fat raindrop smashes into a delicate flying mosquito, the bug is toast, right?

Not if recent experiments by a team of engineers and biologists are any indication. The researchers found that mosquitoes are adept at surviving such collisions, and their work sheds light on why.

That’s good news for mosquitoes, and, say the researchers, it could be useful for humans.

The information could feed into designs for a new generation of tiny robotic fliers tailored for military-reconnaissance or for search-and-rescue work, says David Hu, a mechanical engineer at Georgia Tech in Atlanta who led the effort. The results appeared Monday in the journal Proceedings of the National Academy of Sciences.

Larger drones already have demonstrated their military usefulness in seeking and destroying military targets. Reconnaissance versions fly the border between the US and Mexico and are of keen interest to some big-city police departments. Insect-like robotic fliers would have the ability to go where the larger craft can't – inside buildings occupied by snipers or explosives, or flitting into gaps in debris in a collapsed building to look for survivors.

But it remains unclear how practical such tiny fliers might be.

"There's still a long way to go, even having these vehicles work for short distances," Dr. Hu says. A windy day, or even eddies in the breeze generated as moving air encounters the corner of a house, could send the micro-sentinels flitting off in the wrong direction. Or, as in Hu's query, the tiny fliers could be vulnerable to rainfall.

Previous research had focused on wind-related disturbances to a microflier's performance. But no one had focused on rain. The only moisture-related research involving mosquito-scale insects involved pesticides. Researchers found that to work, liquid pesticides would require drops so small that they penetrate between wax-coated hairs that form a dense layer on mosquitoes, allowing the bugs to ward off water droplets.

Hu's team began by collecting a genus of mosquitoes known as Anopheles. These thrive in the tropics, where rain is frequent. The new home for the insects was a container made from clear acrylic and a mesh top. The team used a high-speed video camera to record the interactions between bug and artificial rain.

Ahead of the experiment, the researchers ran some calculations comparing the size and weight of the droplets and mosquitoes to see if the numbers might shed light on what to expect.

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