Came upon this a few days ago. Researchers at the Georgia Institute of Technology have been studying how mosquitoes, who thrive in humid, rainy climates, are able to fly in the rain. Naturally, when one think of insects and rain, images of cartoon bugs being trapped in raindrops or wings that are too wet to fly are conjured up. Thankfully for the mosquitoes (not so much for those who want a break from the biting) they have more than a few adaptations and physics on their side.
The folks at GT subjected mosquitoes to raindrop attacks while under the watchful eye of a high speed camera. What they saw were two major factors at play. First, insects are naturally hydrophobic. This doesn’t mean that they run away from water, but rather they repel water. They accomplish this by having tiny hairs all over their body, which increase their suface area, and combined with surface tension, cause the water to bead rather than spread. This has been called the “Lotus Effect” because of the similarly hydrophobic properties of lotus leaves. You’ve no doubt seen the effect before:
Mosquitoes are tiny, and raindrops can weigh as much as 2 to 50 times their weight, but this actually works in the little bloodsuckers’ favor. The researchers discovered that due to their small mass, raindrops impart very little force on the mosquito. In anything other than a direct hit, the little insect just rolls out of the way and keeps going. When a direct hit does occur, the mosquito finds itself suddenly accelerating at the same rate as the raindrop. That change in momentum comes out to as high as 300 G forces in 1 milisecond. To put it in perspective, humans can only handle 12 G for about 1.2 seconds before permanent damage occurs.
Alright, so I lied before, at this point the mosquito is trapped in the raindrop, falling rapidly towards the Earth (which unlike the mosquito, does a great job of having momentum imparted upon it). Enter the mosquito’s long legs and wings: As far as wind resistance is concerned, the mosquito is a tiny kite, and it is quickly pulled out of the droplet before it hits the ground. Saved!
So while the trip is bumpy, the average mosquito has no problem navigating its rainy habitat. The research done by the Georgia Institute of Technology will have particularly useful application in nanotechnology and tiny flying robots. You can read their journal article here, and watch the video (slow motion mosquito kung-fu and all) below.
Speaking of watching stuff. As you can see, I am back from a rigorous Festival season, and I come bearing gifts. You can watch replays of many of this year’s Festival programs for free online. If you don’t have 90 minutes to kill, the first batch of clips should be going out sometime next week. Exciting!