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## Mosquitos Have Little Trouble Flying in the Rain186

sciencehabit writes with an interesting article about the (surprisingly not well studied) effects of rain on flying insects. From the article: "When a raindrop hits a mosquito, it's the equivalent of one of us being slammed into by a bus. And yet the bug will survive and keep flying. That's the conclusion of a team of engineers and biologists, which used a combination of real-time video and sophisticated math to demonstrate that the light insect's rugged construction allows the mosquito to shrug off the onslaught of even the largest raindrop. The findings offer little aid in controlling the pest but could help engineers improve the design of tiny flying robots." Bats, unfortunately, aren't so lucky: "...these furry fliers need about twice as much energy to power through the rain compared with dry conditions."
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## Mosquitos Have Little Trouble Flying in the Rain

• #### Impact energy not the same for small objects (Score:4, Interesting)

by Anonymous Coward on Monday June 04, 2012 @11:12PM (#40216449)
A mouse could fall off a building and walk away. People, not so much. The smaller you are, the more resistant you are to long falls. It's why many dwarves become steelworkers.
• #### Re:Impact energy not the same for small objects (Score:5, Interesting)

on Monday June 04, 2012 @11:16PM (#40216463)

You can drop a mouse down a thousand-yard mine shaft; and, on arriving at the bottom, it gets a slight shock and walks away, provided that the ground is fairly soft. A rat is killed, a man is broken, a horse splashes

On Being the Right Size J. B. S. Haldane in 1928

• #### Re:Impact energy not the same for small objects (Score:5, Informative)

on Monday June 04, 2012 @11:50PM (#40216595)
Force = dP / dt P = mass * velocity A mouse weights around ~20g , a horse around ~450kg. If we assume that both of them have the same velocity when touching the floor, the horse will experience a force that is ~22000 times higher. Easily explains the splashing... ( I could go more and calculate an approximation of the value force itself, but I think this is enough )
• #### Re: (Score:2)

If we assume that both of them have the same velocity when touching the floor, the horse will experience a force that is ~22000 times higher.

The total force, yes, but unless I'm thinking about the problem wrong, that force is spread out across a surface area that is somewhere on the order of 3 square inches versus about 12.5-15 square feet (by my very crude estimates), so operating under your assumptions, any given part of the horse's anatomy would experience a force that is only about 30-36 times the force

• #### Re: (Score:3)

If you know the Horse's density and assume he is spherical ( I don't know why this assumption makes me laugh ) you can estimate his terminal velocity, same for the mouse. Now I might be wrong on this one but I would think that roughly both have the same density. If you do a simple calculation this would give you about ~3.5 factor more in favor of the horse ( the horse's terminal velocity following these assumptions would be 3.5 times higher than the one for the mouse). Now the relative surface of two animal
• #### Re:Impact energy not the same for small objects (Score:5, Informative)

on Tuesday June 05, 2012 @01:30AM (#40216895)

(1) The terminal velocities of larger objects is larger, and the effect is significant [wikipedia.org]. The mouse hits the ground at a much lower speed than the horse.
(2) The mouse and horse are not even remotely point particles so you should be considering pressure instead of force. You'd have to divide your 22000 number by the ratio of whatever bits land on the horse at once to the same for the mouse; this would be a fairly large number.

To illustrate very approximately why larger objects have larger terminal velocities, consider two falling spheres of equal density, one of small radius and one of large radius. An object reaches terminal velocity when the energy it gains from gravity is perfectly canceled by the energy it has to give up to move air molecules out of the way. Let's compute each.

Basic physics gives the first line of the following. Constant density and the definition of velocity gives the second, and the formula for the volume of a sphere gives the third.
(energy gained from gravity)
= (gravity constant) * (mass of object) * (distance it fell in a given time)
= (different constants) * (volume of sphere) * (velocity of sphere)
= (different constants) * (cube of radius) * (velocity of sphere)

The other half is more approximate. The first line is pretty much trivial from the setup. The second line is from the formula for the surface area of a sphere and from the basic physics fact that the energy of an object is proportional to the square of its velocity. The rest is algebra.
(energy lost to moving air out of the way)
= (constants) * (amount of air moved per unit time) * (energy imparted to each molecule of air)
= (constants) * [(surface area exposed) * (distance it fell in a given time)] * (velocity of sphere squared)
= (constants) * [(radius squared) * (velocity)] * (velocity squared)
= (constants) * (radius squared) * (velocity cubed)

At terminal velocity, these two are equal. Simple algebra gives the answer from here.
(constants) * (cube of radius) * (terminal velocity) = (constants) * (square of radius) * (cube of terminal velocity)
(constants) * (radius) = (square of terminal velocity)
(terminal velocity) = (constants) * sqrt(radius)

The large sphere has large radius, so large terminal velocity. Incidentally this is the formula from the Wikipedia page I linked, though my assumptions were very, very approximate and are probably different from the ones used to derive it.

• #### Re:Impact energy not the same for small objects (Score:5, Funny)

on Tuesday June 05, 2012 @03:12AM (#40217203)

Okay, there's only one way to settle this once and for all. BRB

• #### Re: (Score:2, Insightful)

by Anonymous Coward

Simplify the experiment.
F=M*A
Given two objects of equal velocity, the more massive imparts more force.
The determining factor in the bounce vs. splash is how much energy is required to destroy the cellular bonds.
Assume both objects are spherical with the same composition and density, and no outside forces such as gravity or air resistence, etc. This also allows us to assume the same amount of force applied to a given surface area upon impact.

If the velocity is low enough, neither object will impact with enou

• #### Re:Impact energy not the same for small objects (Score:5, Funny)

on Tuesday June 05, 2012 @08:19AM (#40218455) Journal

A man, a horse, and a mouse walk into a bar...
"Here you are," the barkeep says as he gives him the beer and keys to to roof.

Then he looks at the horse and asks "Why the long face?"
The horse pondered for a moment and then replied

"Well, basic physics gives the first line of the following.
Constant density and the definition of velocity gives the second, and the formula for the volume of a sphere gives the third.
(energy gained from gravity)
= (gravity constant) * (mass of object) * (distance it fell in a given time)
= (different constants) * (volume of sphere) * (velocity of sphere)
= (different constants) * (cube of radius) * (velocity of sphere)

The other half is more approximate. The first line is pretty much trivial from the setup. The second line is from the formula for the surface area of a sphere and from the basic physics fact that the energy of an object is proportional to the square of its velocity. The rest is algebra.
(energy lost to moving air out of the way)
= (constants) * (amount of air moved per unit time) * (energy imparted to each molecule of air)
= (constants) * [(surface area exposed) * (distance it fell in a given time)] * (velocity of sphere squared)
= (constants) * [(radius squared) * (velocity)] * (velocity squared)
= (constants) * (radius squared) * (velocity cubed)

At terminal velocity, these two are equal. Simple algebra gives the answer from here.
(constants) * (cube of radius) * (terminal velocity) = (constants) * (square of radius) * (cube of terminal velocity)
(constants) * (radius) = (square of terminal velocity)
(terminal velocity) = (constants) * sqrt(radius)

The large sphere has large radius, so large terminal velocity. Incidentally this is the formula from the Wikipedia page I linked, though my assumptions were very, very approximate and are probably different from the ones used to derive it.

In summary, this asshole is going to shove me off a roof just to prove a point, physics says they'll both survive, but I'm fucked."

• #### Re:Impact energy not the same for small objects (Score:5, Funny)

on Tuesday June 05, 2012 @04:20AM (#40217413)

Force = dP / dt
P = mass * velocity
A mouse weights around ~20g , a horse around ~450kg. If we assume that both of them have the same velocity when touching the floor, the horse will experience a force that is ~22000 times higher. Easily explains the splashing... ( I could go more and calculate an approximation of the value force itself, but I think this is enough )

Yes. But the real question is: What would happen to a bag filled with 22,500 mice (weighing a total of 450kg)?
Would the mouse-bag make a splash like the horse? Or would each individual mouse walk away with a slight shock?

• #### Re:Impact energy not the same for small objects (Score:5, Interesting)

on Tuesday June 05, 2012 @04:36AM (#40217451)
That's way more complicated. You are talking about an n-body ( n= 22500 ) dynamics, if I am not mistaken this can be best handled by fluid dynamics. But even that is based on a lot of assumptions, for example will the bag hold ? if yes then it will behave like the horse. If not, then it depends on how fast will it tear, and how will it tear! Try this, take a melon and throw it out of a 10 story building, then another melon in ten plastic bags, and another in 100 plastic bags, and throw them. The result will show you what I mean.
• #### Re: (Score:2)

Not necessarily true. We are talking about a value well under Avogadro's number. Even if we had enough mice, the inter-particle interactions would be highly non-newtonian. For 22500 mice, I would still model them as solid particles (it can be done, and is not quite as hard as you might think). The effects on individual mice would be quite interesting, in my estimation. Individuals on the leading surface of the bag would be expected to bear the brunt of the impact, while his/her compatriots at the rear

• #### Re:Impact energy not the same for small objects (Score:5, Insightful)

on Tuesday June 05, 2012 @04:34AM (#40217447)
Yeah but if you assume that they touch the floor at the same speed, the amount of energy to be absorbed per body weight is the same for mouse and horse. The force per body weight is even lower for the horse since it has longer legs and therefore more time to slow down. But also the ratio of the cross section of the legs to the body weight is worse, which makhttp://science.slashdot.org/story/12/06/05/0112252/mosquitos-have-little-trouble-flying-in-the-rain#es it worse for the horse again.
• #### Re: (Score:2)

When asked about it, the horse replied, "No sir, I didn't like it."
• #### Re:Impact energy not the same for small objects (Score:4, Funny)

on Tuesday June 05, 2012 @08:21AM (#40218459)

Excellent, so I can toss mice off the top of my building all day long and not have to worry about killing them.

Suck it PETA. Throwing these mice is intrinsic to testing the catacopter.

• #### Re:Impact energy not the same for small objects (Score:5, Funny)

on Monday June 04, 2012 @11:51PM (#40216599)

Dropping a bus on a horse, a human or mouse at the bottom of a thousand-yard mine shaft will still wreck the bus. Wouldn't be good for the creatures either (probably kill the mosquito too).

• #### Re: (Score:2)

You can drop a mouse down a thousand-yard mine shaft; and, on arriving at the bottom, it gets a slight shock and walks away, provided that the ground is fairly soft. A rat is killed, a man is broken, a horse splashes

On Being the Right Size J. B. S. Haldane in 1928

Sextus Empiricus could have told us that 1750 years sooner if he had a mouse, a rat, a spare horse and a thousand-yard mine shaft.

• #### Re: (Score:2)

I know a guy who as a child "saved" his guinea pig from an incoming dog by throwing it out the balcony.

It didn't survived.

• #### Re: (Score:3)

You can drop a mouse down a thousand-yard mine shaft; and, on arriving at the bottom, it gets a slight shock and walks away, provided that the ground is fairly soft. A rat is killed, a man is broken, a horse splashes

On Being the Right Size J. B. S. Haldane in 1928

to be fair, the world has changed since 1928. These days, a man splashes.

• #### Re:Impact energy not the same for small objects (Score:4, Informative)

on Tuesday June 05, 2012 @06:09AM (#40217745)

A mouse could fall off a building and walk away. People, not so much. The smaller you are, the more resistant you are to long falls.

Close.... the lower your mass to surface volume density; the more resistance you are to long falls.

The most resistant objects to long falls are very large organisms that have very little mass, and therefore a higher ratio of surface volume to mass.

The larger the object's horizontal cross-section w.r.t the ground, the greater the air resistance, the lower the velocity while falling.

The lower the velocity towards the ground while falling, the lower the change of momentum at the point of impact.

The lower the mass of the object, the lower the change of momentum at the point of impact with the ground.

The lower the change of momentum at the point of impact with the ground, the lower the upward force that is exerted upon the object in the collission.

The difference in damage between the two objects then depends on what the two different objects were constructed from. Different materials have different strengths; a titanium skeleton will probably fair better than something made out of fired clay.

• #### Figures. (Score:5, Funny)

by Anonymous Coward on Monday June 04, 2012 @11:14PM (#40216453)

You have to work your ass off to keep the things you like alive/going (plants, cars, house, etc), yet pests like mosquitoes, bankers, and politicians you just can't get rid of no matter how hard you try.

• #### This is new? (Score:2)

I thought anyone who has ever been fishing already knew that?

Fishing in light to medium rain still ends up getting you rather bitten at dusk and dawn during mosquito season.
• #### Re: (Score:2)

Yup. Rain doesn't stop the little buggers at all. To add further insult, it washes off the insect repellent too.

• #### /. editors: Too many games, not enough reality (Score:2)

"When a raindrop hits a mosquito, it's the equivalent of one of us being slammed into by a bus."

You know that's not true. A bus is solid, a raindrop is liquid.
• #### Re: (Score:3)

Surface tension is a rather interesting study of fluids.
• #### Re:/. editors: Too many games, not enough reality (Score:5, Interesting)

on Monday June 04, 2012 @11:29PM (#40216519)
But the bus analogy is still wrong, because the entire point of the article is that the mosquito is not smashed by the raindrop. Instead the mosquito simply merges into and falls with the drop, then escapes before the raindrop hits the ground.

So, it's more like phasing through the front of an oncoming bus, landing comfortably in one of the seats, then escaping out the rear before the bus plows into a concrete wall.
• #### Re:/. editors: Too many games, not enough reality (Score:5, Funny)

on Monday June 04, 2012 @11:44PM (#40216571)

*sigh* I don't understand these bus analogies. Can someone please give me a car analogy instead?

• #### Re: (Score:3)

Just substitute bus by Ford F150 or Hummer, that's all

• #### Re:/. editors: Too many games, not enough reality (Score:5, Funny)

on Tuesday June 05, 2012 @02:44AM (#40217133)

But the bus analogy is still wrong, because the entire point of the article is that the mosquito is not smashed by the raindrop. Instead the mosquito simply merges into and falls with the drop, then escapes before the raindrop hits the ground.

So, it's more like phasing through the front of an oncoming bus, landing comfortably in one of the seats, then escaping out the rear before the bus plows into a concrete wall.

*sigh* I don't understand these bus analogies. Can someone please give me a car analogy instead?

It's like a raindrop that hits a Yugo. The raindrop merges into the Yugo. The Yugo stops because the electricity fails. You get out, a little wet because of the leaking roof, but still OK.

• #### Re: (Score:3)

Well, the mosquito would probably survive (the impact, not the drowning) when the drop it is in hits the ground, too. I often hit when I swat at flies (which are bigger and heavier than mosquitos), and they simply butt into the wall (with, relatively, quite some force), shake their head, curse at me and simply continue buzzing about.

These little things are built like tanks, I tell you.

• #### Re: (Score:2)

Depends on what they hit I guess. I'd have thought they'd be pretty screwed if they landed in a puddle, or pretty much anywhere which did not fling them free of the water at the point of impact.
• #### Re: (Score:2)

Yes, but a mosquito is solid and a human, in this scenario, is liquid.

• #### Re: (Score:3)

Physics doesn't scale by size either. Strength is related in different ways to length and to cross section, which is length (or breadth) squared. Mass is proportional to length (or breadth) cubed. That's not even remotely the same. Dropping a bug a meter is not like dropping an elephant a hundred meters.

• #### Re: (Score:2)

True, the analogy is wrong.
They should calculate how much water that would be , and what the effect would be on human beings.

One thing to take into account is the position of the body and area of impact : I have a feeling that if you put the amount of water on someone head while standing up, it would be harder to withstand than if you were crouched down , and the water is put on your back.

• #### Re: (Score:2)

Would you have preferred that they used a tanker truck instead of a bus?
• #### Why don't they? (Score:2)

Well that leads to the obvious question then, why don't they? They seem to disappear quite quickly when it starts raining.

• #### Re:Why don't they? (Score:5, Funny)

on Monday June 04, 2012 @11:48PM (#40216583)
Not where I live. When it rains, it only makes them more vicious. And the hotter/wetter it gets, the worse they are. It is unbelievable, they fly in packs of five, four lift the blanket by the edges, one sucks. Then they change.
• #### Re: (Score:2)

Because when it's raining, they're off to the puddles to make sweet, sweet love and deposit thousands upon thousands of eggs, I suspect.

Also, I may well be able to survive a good batting with a foam LART, but that doesn't mean I like it.

• #### I for one... (Score:2)

From the article:

The findings offer little aid in controlling the pest but could help engineers improve the design of tiny flying robots.

I, for one, welcome our new insect overlords.

• #### Re: (Score:2)

Finally we may beat the mosquitoes by fighting them with tiny anti-mosquito UCAVs.

• #### The Wooden Wonder (Score:5, Funny)

on Monday June 04, 2012 @11:21PM (#40216485)

Yes, Mosquitos could fly in the rain. However they would have trouble dropping their bombs accurately and obviously the recon version wouldn't get good photos.
The night fighter version would fare better with its radar, if there were any German bombers up there to intercept.

But of course sometimes they had to fly in bad weather, such as just before D-Day.

• #### Mosquito's secret weapon (Score:3)

on Monday June 04, 2012 @11:32PM (#40216537)
It's all the Scotchguard they spray themselves with.
• #### Re: (Score:2)

Just after reading the headline i half expected that they were going to say the erratic way they fly provided a bonus against ever hitting a raindrop.

Oh well, sustaining the impact is cool, too.

• #### Here's the video for it ... (Score:4, Informative)

on Tuesday June 05, 2012 @12:20AM (#40216685)
• #### Matter of chance (Score:4, Insightful)

on Tuesday June 05, 2012 @12:55AM (#40216803)
If mosquitos weren't able to deal with rain, there wouldn't be a lot of mosquito's. They need water to reproduce in so they live in predominantly wet areas. Evolution made the rain resistant mosquito's breed and the non resistant ones extinct. Horses don't often fall down steep cliffs, nor do humans, so there isn't a lot of reason for them to develop a resistance against that. Mice reach their terminal velocity rather quick, so if they survive a 2m drop, they are much more likely to survive a 200m drop, since the difference in velocity isn't that much.
• #### Re:Matter of chance (Score:5, Funny)

on Tuesday June 05, 2012 @02:58AM (#40217169) Journal
Stiiiinging in the raiiiin, I'm Stiiiinnning in the raiiiin...
• #### Re: (Score:2)

Explain the Pegasus then.

• #### Tiny Flying Robots? (Score:4, Insightful)

on Tuesday June 05, 2012 @02:20AM (#40217055) Journal

The findings offer little aid in controlling the pest but could help engineers improve the design of tiny flying robots.

Great! Because I was just thinking to myself, "we really need more tiny flying robots. If I have to wait 20 years for the CIA to solve the raindrop problem and weaponize these things, I'll die of boredom before videos of them assassinating people with them show up on YouTube."

Too heavy on the sarcasm? Fortunately I don't say stuff like this out loud.

• #### Re: (Score:2)

The findings offer little aid in controlling the pest but could help engineers improve the design of tiny flying robots.

Great! Because I was just thinking to myself, "we really need more tiny flying robots. If I have to wait 20 years for the CIA to solve the raindrop problem and weaponize these things, I'll die of boredom before videos of them assassinating people with them show up on YouTube."

Too heavy on the sarcasm? Fortunately I don't say stuff like this out loud.

FWIW (not much), it would probably be easy to weaponise actual mosquito's than to try and reproduce them as robots. Make a few billion sterile females, load them up with some form or malaria or plague that can't possibly be transmitted by regular mosquito's, and drop them on the enemy. What could possibly go wrong?[1]

[1] For the humour impaired, that's a rhetorical question. I'm well aware of what could go wrong

• #### Water Spritzer (Score:2)

So I guess my water spritzer isn't a good bug fighting weapon after all. Back to the wash cloth I guess :(
• #### Re: (Score:2)

Add a bit of soap to the water. That tends to work a lot better in my experience, the insects get wet instead of having the water slide off.
• #### Effect of Rain on Mosquito Behaviour (Score:5, Funny)

<hyades1@hotmail.com> on Tuesday June 05, 2012 @04:08AM (#40217365)

In Winnipeg, it isn't that mosquitoes can't fly in the rain, they just don't like it very much. Usually, your basic Winnipeg mosquitoes just jack a car and drive to their next victim. If the driver's lucky, the mosquitoes will let him go instead of keeping him for an en route snack. If there's a dog or cat in the car...don't ask. It won't be seen again.

• #### speed of an ant (Score:2)

If a human could cover the same number of the lengths of his body as an ant per the same amount of time, he would run at the speed about 1500 km/h (about 1000 miles/h).

There are a lot of such phenomena in the wild life world. It is one more reason to protect biodiversity, so that these species do not disappear and could be studied by engineers in the future.
• #### Re: (Score:2)

If a man were the size of an ant, he'd be able to run the same speed. The "feats" of insects aren't due to incredible adaptations, they're due to you extrapolating using the wrong function.

• #### Re: (Score:2)

There is a lizard which can hold the upright position no matter how it dropped on the floor. More than that it can hold it in the wind tunnel with artificial turbulence.

I listened to a radio show on this topic at http://itc.conversationsnetwork.org/ [conversationsnetwork.org] . It is being studied already, but engineers cannot get it how it works so far. They say this threatened lizard should be definitely preserved for studying by smarter engineers in the future.

Still my claim hold, it was: If a man could cover the same number
• #### Re: (Score:2)

There ARE incredible adaptations out there, it's just that the "if a \$YOUR_CHOICE_OF_SMALL_INSECT were the size of a man it could \$AMAZING_FEAT_HERE" stuff isn't. It's simply a meaningless linear extrapolation when the proper function is quadratic or cubic (or higher).

Yes, if a man could cover the same number of lengths of his body as an ant in the same amount of time, he might be running 1500 km/h. So? If the Empire State building could cover the same number of lengths of it's height as I can when runni

• #### Re: (Score:2)

Another interesting observation about insects is that the intelligence of their movement is imbedded, hardwired, into the mechanical structure of their body. They think very little by brain when they move with large number of legs.

And ants communicate with smells. They emit molecules which transmit meaning for them. Sometimes they even connect antennas, as if creating one organism from several ones, to discuss faster.
• #### Terrible analogy (Score:4, Insightful)

on Tuesday June 05, 2012 @06:23AM (#40217799)

When a raindrop hits a mosquito, it's the equivalent of one of us being slammed into by a bus. And yet the bug will survive and keep flying.

In other words, it's definitely not the equivalent being slammed by a bus.

• #### Seen the video (Score:2)

Still can't believe the mosquito survived without its wing being ripped off.

• #### Oh come on... (Score:2)

You mean the summary couldn't give us even a tiny hint about how the mosquito can fly through rain?

If I wanted to go read articles, I'd be reading articles right now instead of being on /. with a mouthful of bagel.

• #### Re: (Score:2)

I feel your pain, brother. This post [slashdot.org] seems to be the most comprehensive, quoting a good bus analogy by someone claiming to have RTFA. ;o)

• #### Old news. (Score:3)

on Tuesday June 05, 2012 @08:25AM (#40218497) Journal
Mosquitos can easily fly in rain, and also in fog and snowy conditions too. In fact the Mosquito was faster than all the German fighter planes chasing it. So they completely dispensed with all the defensive machine guns, improving its bomb payload. Darned good for something made of plywood and glue. Later they painted it black and used it as night bomber.
• #### The Hellstrom Chronicle (Score:2)

I'm not sure if this is buried in a comment elsewhere, but I wanted to forego modding to point out an Oscar-winning "documentary" that (sort of) examines this question: