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How mosquitos deal with getting hit by raindrops (nationalgeographic.com)
404 points by davi on June 25, 2015 | hide | past | web | favorite | 79 comments

Of course the video doesn't show anything interesting, the mosquito's leg is hardly even grazed. I was definitely hoping for the version where a drop smacked the insect dead on target. Fairly strange for a lab result - if that's the only video that was captured, it really doesn't seem to divulge much at all. Where's the cool video? :D

Direct hit just after the minute mark: https://youtu.be/LQ88ny09ruM?t=1m3s

Watching it several times, it looks like only the left most mozzie came out unscathed. The other two took it hard and went down... definitely didn't 'walk off the bus' :\

I was checking out that Andrew Dickerson dude's Youtube channel - https://www.youtube.com/user/andrew52987/videos - it's like a showcase for mosquito torture!

Check out this one: https://www.youtube.com/watch?v=8s1_f9fyjME

Yeah it's weird especially since you just get done reading about how they get away with getting hit between the wings and then you get told "if you want to see this for yourself, watch the video" ... lol

Still a good read with fun drawings :)

To me it looked like he linked the wrong video accidentally, since it didn't match up with the text at all.

>A study says a mosquito being hit by a raindrop is roughly the equivalent of a human being whacked by a school bus, the typical bus being about 50 times the mass of a person.

That is not a sensible comparison. When you scale something mass changes as the cube of dimension. Strength changes as the square of dimension. So small things are inherently stronger with respect to their mass.

This is slightly misleading - strength actually changes as the square of the dimension or the cube of the dimension, depending on which strength you're talking about.

Axial (tension, compression) and shear strength are derived from net area and so scale with by x^2. Flexural strength is derived from a factored second moment of inertia which happens to work out to x^3.

Thanks for the math to back up my own doubt. Fortunately, the bus analogy appears to be added by the author as a bit of sparkle and does not get brought up again.

I think it's a good analogy to have.

You don't have the same results from bus:human::raindrop:mosquito, but the size comparison is a useful measure. I didn't realize a raindrop was 50x the mass of a mosquito. I thought they were roughly the same size.

Further, it reinforces or introduces the idea (along with the conclusion of the study) that "So small things are inherently stronger with respect to their mass."

Lastly, this is National Geographic. Anecdotes and analogies are useful to communicate to the general public.

>That is not a sensible comparison.

Well yeah, since the mosquito evidently survives...

[Citation Wanted]

Very believable; how does the math work out?

Galileo. Discourses and Mathematical Demonstrations Relating to Two New Sciences. 1638.

It's known as the square-cube law.


Thanks - I hadn't realized that muscle strength was proportional purely to cross section.

> But because our mosquito is oh-so-light, the raindrop moves on, unimpeded, and hardly any force is transferred. All that happens is that our mosquito is suddenly scooped up by the raindrop and finds itself hurtling toward the ground at a velocity of roughly nine meters per second, an acceleration which can’t be very comfortable, because it puts enormous pressure on the insect’s body, up to 300 gravities worth, says professor Hu.

Interesting article, but in the span of one paragraph here we have confused velocity, acceleration, and pressure - and there are similar errors in the following one. For an article about physics, I would expect this to at least be proofread.

The Gell-Mann Amnesia effect: http://harmful.cat-v.org/journalism/

It is pretty sloppy, but if you assume that `pressure' is just meant as a synonym for `strain', which it is in normal English, it does make some sense. And velocity and acceleration aren't confused under a very charitable interpretation: they describe that the velocity changes `suddenly'. That's an acceleration.

The real problem is here:

> But because our mosquito is oh-so-light, the raindrop moves on, unimpeded, and hardly any force is transferred.

We have a transfer of momentum (force times time), but no dissipation of energy (force times path).

> We have a transfer of momentum (force times time), but no dissipation of energy (force times path).

Even the transfer of momentum is much less than it would be if the mosquito were heavier though. The droplet maintains most of its original momentum. That seems to be the point they're trying to make.

Yes. Though for the mosquito it doesn't matter: transferring momentum doesn't damage you.

An interesting human scale contrast is the following:

You have (a) a heavy metal box or (b) a light wooden box and you throw (1) a bouncy rubber ball or (2) an equally heavy piece of clay at it. What happens in all four combinations?

One observation: the rubber ball transfers more momentum, but almost no energy.

From your link:

> In any case, you read with exasperation or amusement the multiple errors in a story, and then turn the page to national or international affairs, and read as if the rest of the newspaper was somehow more accurate about Palestine than the baloney you just read. You turn the page, and forget what you know.

Which is of course intriguing, since cat-v.org hosts frothing-at-the-mouth vitriol about topics like women in tech and gay marriage in the always trustworthy and well reasoned medium of reposted reddit and slashdot comments. And presumably I'm supposed to click over to the technical stuff with a straight face.

It's telling that you'd apply a derogatory label and attack the source medium rather than say anything of substance about the content that offended you.

cat-v is chock-full of food for thought. You don't have to agree with any of it and in fact disagreement is a large part of the site.

"Other than total and complete world domination, the overriding goal is to encourage and stimulate critical and independent thinking."

Upon encountering the frothy-mouthed bits, you could return to the gell-mann-amnesia-effect node, and treat it as a disclaimer.

Better coverage of the same research can be found here [0], with no statements such as "300 Gs is a crazy amount of pressure"

[0] http://io9.com/5916251/why-can-mosquitoes-fly-in-the-rain

From an io9 article on the same research:

>> [Hu] and Dickerson constructed a flight arena consisting of a small acrylic cage covered with mesh to contain the mosquitoes but permit entry of water drops. The researchers used a water jet to simulate rain stream velocity while observing six mosquitoes flying into the stream. Amazingly, all the mosquitoes lived.

The researchers used simulated rain drops on six mosquitoes. There are more than six species of mosquitoes. They controlled for wind effects (which are part and parcel of rain). So they excluded horizontally travelling raindrops. My immediate reaction to the conclusion that mosquitoes can fly in rain was "Really? Not always". Here is a methodologically lacking and wholly unscientific anecdote: I have lived in Johannesburg my entire life, where mosquitoes are quite prevalent during the summer months. When it is raining heavily (it is usually quite windy as well), the local species of mosquito that feeds of humans do not present a problem as the number of airborne mosquitoes tends to zero.


I live in a mediterranean zone near a huge lake and during summer mosquitos are your every night companions (specially if you're working during late night hours). But when a summer storm brews the mosquitos disappear for two or three days. Why? This has been for me a recurrent question, and the answer has been always obvious: few of them survive being hit by raindrops.

You can make 1000 theories about how our tiny vampire friends deal with raindrops, but it's pretty clear that intensive rain (>3hours) wipe out mosquitos population for several days...

I can't discuss how the rain interacts with the adults, but I have read scientific research that discusses how stagnant water is required for mosquitos to lay eggs and for the larvae to breathe. If the surface of the water ceases to be stagnant, the eggs cannot be laid and the larvae will suffocate.

I retrieved a link to an article last year that discusses a device that uses solar power to aerate ponds as a mosquito preventative [1].

A reasonable conclusions for the drop in population is therefore that two generations can be severely depopulated by a heavy rainstorm, leaving only the portion living in stagnant water that is sheltered from the rain and run-off to survive and repopulate.

1. http://www.wired.co.uk/news/archive/2014-05/19/mosquito-devi...

I also agree.

> "And yet (you probably haven’t looked, but trust me), when it’s raining those little pains in the neck are happily darting about in the air, getting banged—and they don’t seem to care."

I have looked and I don't trust you. I live in Brazil where mosquitoes are present all the time, even in the city (obviously, on a smaller scale than places closer to nature). I do notice that whenever is raining there is a sharp drop in mosquitoes number flying inside our homes. They don't completely disappear, but is notorious they are in much smaller numbers. As this is common knowledge over years and years, across basically all the people, I don't consider it anecdote, but empirical observation.

I cannot answer if that is because raindrops kill them, or they just preserve themselves sheltered in their nests, or they breed less in rainy days, or whatever. But the article (not sure about the research) is based on a false premisse.

Well, no, it's not empirical until we design some experiments to test the theory, make predictions, test them, come up with potentially observable data that would falsify our hypotheses, publish our results and let them be peer reviewed, reproduced elsewhere etc... The jump from anecdotes to empiricism is a large one that is not to be undertaken lightly.

It seems likely. Mosquitoes have like 3 neurons, and can't be built to deal with macroscopic events. More likely the species uses simple statistics to survive: enough eggs laid in enough places will survive the harshest downpour. The flying guys are only there to lay eggs after all. Seen from that angle, a mosquito is an eggs way of making another egg. Dying in rainstorms is not a problem.

Surviving is not the same thing as actively seeking food.

I'm guessing it still sucks for them.

"Had the raindrop slammed into a bigger, slightly heavier animal, like a dragonfly, the raindrop would “feel” the collision and lose momentum. The raindrop might even break apart because of the impact, and force would transfer from the raindrop to the insect’s exoskeleton, rattling the animal to death."

Has anyone actually done any research on dragonflies being hit by raindrops, or is this just speculation?

The drawings in this article tend to be absurdly large, with the outcome that the document is, transferred, around 23MB, for no good reason. Sigh.

Because editors.

> In most direct hits, Hu and colleagues write, the insect is carried five to 20 body lengths downward

> If you want to see this for yourself, take a look at Hu’s video

What? Nothing like that happens in it.

The author might have had in mind some other video while writing that. This is another video from that same researcher that shows this: https://youtu.be/LQ88ny09ruM?t=1m5s

Are you confusing wing span with body length?

In the right hand panel of the video, the insect certainly moves several body lengths, and is still moving downwards at the end of the clip.

No, it says "20 body lengths downward, and then [...] gets up and “walks” to the side, then steps off into the air". In other words 20 body lengths while being in the raindrop, which doesn't happen in the video. In fact, the raindrop barely touches it.

If it wasn't for the cute child like drawings this would be a truly terrible piece of link bait. As it is it's still pretty and, and I expect better from NatGeo.

Anyone who lives in a mosquito heavy area knows that mosquitos (like almost all airborne insects) go into hiding during heavy rain and/or wind.

Does this places a reasonable selection pressure on the kinds of flying insects we can have?

Big enough to shrug off a raindrop hit, or small enough to surf along the surface tension until it can slide off?

It would appear they haven't yet evolved to deal with being hit by cars quite as gracefully.

I think this can be approached the same as the "ants can lift 50 times their own weight" bit of trivia. It doesn't translate to "if a human were as strong as an ant he'd be able to lift an elephant" because size doesn't scale that way. Ants and mosquitoes get away with larger forces relative to their mass because the skeleton and muscles needed are still within reasonable material and fuel costs. A human-sized animal that wanted to survive being hit by a car would need to spend much more energy per mass than the insect does.

I think theVirginian was commenting about mosquitoes getting smashed on a car's windshield, not about cars and humans.

Oh, right. I thought it was a reference to "the equivalent of a human being whacked by a school bus" from the article.

I just realized how making things fun and funny can help to teach anything. The drawings and the comical tone made this seem so approachable. I wish they had a series of 1000 of such lessons I could read.

Here's his old blog on NPR: http://www.npr.org/sections/krulwich/

Probably not 1000, but perhaps getting on for it.

Thank you for sharing.

Not really important but.. "nine gravities (88/m/squared)"

I don't get it, the scientificamerican blog that they are quoting has the right units, where did they come up with this?

> But because our mosquito is oh-so-light, the raindrop moves on, unimpeded, and hardly any force is transferred.

So if the mosquito's weight is insignificant compared to that of the heavier and denser water drop and that's what keeps it from having the force transferred, would this equally apply to hailstorms? (Where our mosquitoes are pelted by small hail balls the size of raindrops)

You don't really find mosquitoes where you're likely to find hailstorms.

Are you thinking of sleet? Hail is associated with severe thunderstorms,[1] which definitely occur in areas with mosquito populations.

[1] http://www.accuweather.com/en/features/trend/hail-or-sleet-h...

In Spain we definitely have mosquitos, and most Augusts we have these summery storms, sometimes bringing also hailstorms (sizze varies though between drop sized ice and golfball sized ice)

You find them in these areas. When it gets cold there tends to be far fewer of them.

And compared to the equators its nearly incomparible.

Cold isn't required for hailstorms. The ice forms at altitude. We have a lot of hailstorms in the spring and summer in Colorado, and while it isn't the mosquitoiest place I've ever lived, there are mosquitoes.

Compared with where its mosquito haven like by the Equator?

I suppose raindrop vs hailstone is a reason is one of the reason's the density issues are so different.

Yeah. Mosquitoes are densest in the tropics where hailstorms are rare, but just about everywhere on earth short of Antarctica has some mosquitoes. I'd think mosquitoes would meet hailstones occasionally, though I can't really see the mosquito surviving it.

I just returned from a vacation in Wyoming where we were hit by a number of hailstorms, not to mention more common thunderstorms (it was a VERY wet and cold May). Still had to deal with mosquitos (but not nearly as bad as in mid-late summer).

Neat plastic bubble that where you live in!

I'd like to see you compare the density of mosquitoes in colder climates to those close to the equator.

I'd like to see you not really finding mosquitoes where you're likely to find hailstorms.

The article embedded a short video. Here's longer video with explanations: https://www.youtube.com/watch?v=LQ88ny09ruM

Can't help but immediately notice: "Drawing by Robert Krulwich"

Yes, Robert Krulwich has joined the Nat Geo Phenomena blogging platform [ http://phenomena.nationalgeographic.com/blog/curiously-krulw... ]

I think the commenter meant that Krulwich actually illustrated the piece too. Who knew Krulwich could draw!

Ah, I see. My bad.

Yes, Krulwich does draw pretty well.

if you like watching slo mo videos, recommend this channel: https://www.youtube.com/user/theslowmoguys/videos

so if mosquiotos are oblivious to rain is there some way to make artificial rain with different properties that could destroy mosquitos en masse?

Yes, it's called poison and it's being done a lot.


Ah you mean different mechanical properties ;)

Anything that causes the water to stick to them rather than letting them bounce off should work. Just mixing in a little soap maybe?

Send this to Bill Gates, that guy HATES mosquitoes.

A man who thought, "When I'm a billionaire, I'm going to dedicate my life to getting rid of those nasty fuckers (mosquitoes)" and then did it.

very interesting article. It is a pity that his column has no rss feed.

A commenter on the site says that some type of mosquitoes (Texas) are used in oil drilling. I tried googling "texas mosquitoes oil drilling" and variants, but didn't find anything.

>"Why, one species even secretes an enzyme to dissolve the organic matter in blood leaving only the iron in haemoglobin. Then another enzyme causes the iron atoms to join to form biological drill pipe! These structures are known to be as much as 6 inches in diameter and to extend a mile deep."

Is there something to it or he just went to on the internet to tell lies?

That is a joke that makes more sense once you've been bitten there.

Then there's the one about the mosquito that landed at [local air force base] and the fuel truck was half-way to it before they noticed it wasn't a fighter jet.

In Texas, we'd call that a tall tale.

Up north a few winters back the weather was so cold that words froze up as you talked. People had to stand around a fire to have a conversation. When spring thaw finally came the sound of all the melting conversations was deafening.

Then there was the time that Pecos Bill lassoed and rode a twister, but that's a tale for another time.

I laughed for a good minute after reading your comment... Hope it counts!

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