August 17, 2010 • 24 mins
Why do mosquitoes love biting certain people (and ignore others)? In this podcast, Robert and Allison take a closer look at the science behind mosquito bait. Tune in and learn why insects love -- or loathe -- biting you.
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Speaker 1 (00:01):
Welcome to Stuff from the Science Lab from how stuff
Works dot com. Hey guys, welcome to the podcast. This
is Alice and I don't know like the science editor
how stuff works dot com. And this is Robert Lamb,
science writer's how stuff Works dot com. And we are
(00:23):
podcasting to you from the Georgia summer means and mosquito. Yes,
lots of mosquitoes, So let's talk about the obvious question
out there. Do you mosquitoes flocked towards you? That seems
to be like, like, anytime I'm in an outdoor event
like that and someone gets bit in my mosquito, that's
like the instant conversation topic because someone's always like, I'm
(00:44):
mosky debate or they'll be like, normally I get bitten
by mosquitoes and my husband doesn't, or you know, it's
vice versa. I mean, it's something we all have some
experience with. I don't think any of us have necessarily
figured it out. So I had my Emma staying with
us a few weeks ago, and my mother in law
happens to be one of the people who she says,
(01:04):
mosquitoes flack to and she gets a lot of bites
and no kidding. She went up to um sort of
this loft spare room area that we have a whole
bunch of our stuff in and also our lovely guests
get to stand. And actually, no, that's the point. I mean,
nothing's really, nobody's really ever up there. You know, we
never go up there. There's a fan going, you know,
(01:25):
so maybe the fan would deflect mosquitoes. But she went
up there and within minutes she was bitten five times.
I felt bad, I felt terrible. I felt like she lived,
you know, she thought we lived in some you know,
mosquito ridden hobble. But I think they really do like her. Wow.
And and that comes down to the interesting question do
mosquitoes really like some people more than others or is
(01:47):
this just kind of um, you know barbecue hearsay, Well,
you can you can count on science to get to
the bottom of some of these mysteries. So we did
a little digging, and as it turns out, they really
do exhibit a preference for certain folks. So there was
a In Chee thousand one, a guy by the name
of David W. Kelly published a paper in Trends in Parasitology,
and it was called, appropriately enough, why are some people
(02:10):
bitten more than others the scientists and their titles. That
was a pretty good one. Um. In this case, Kelly
says humans will get bitten by blood sucking insects, and
frequently all of us are going to get a bite, right,
nobody's immune to it, but a special subset of that
population will be quote unquote heavily attacked. Okay, so let's
(02:30):
quantify the numbers that that Kelly starts stirring around in
this paper. So put ten people in a room with
say some anopolies mosquitoes, and those are the notorious specters
for the malarial parasite plasmodium, and or two of those
people in that room are going to be responsible for
passing on eight of the disease. Okay, so let's let's
talk about it again. Two people are going to pass
(02:52):
on eight of the disease according to a Woolhouse at all.
So if that's pretty crazy and so, I mean, that
does seem to point or the idea that, yes, in fact,
mosquitoes do exhibit a preference from a public health perspective.
Imagine if you could really home in on that and
figure out what makes them so attractive. I mean, not
only would you know mosquitoes or companies interested in mosquito
(03:15):
control will be hugely interested in this, but the rest
of us would want to hang out with them, like
their mosquitoes everywhere. Call up, Charlie, I want him standing
next to me, right and you know, mosquito bits are
annoying and we're kind of kidding at it, but you know,
when you think about all those people dying from malaria
or other mosquito born diseases, really stinks. Well, this is interesting, um.
(03:37):
And this is a slight tangent here, but I ran
across a really cool argument for mosquitoes, because mosquitoes are
one of the things you're frequently here, like why do
we have mosquitoes? Like if you know, if if there's
a god in heaven wanted he create mosquitoes, that kind
of thing. Um. But one one interesting argument for them
is that mosquitoes and their malaria have kept humans out
(04:01):
of certain areas of the world for long periods of time,
or at least kept them from expanding into those areas
in large numbers. So the argument is that if you're
you know, um, an environmentalist or you know a tree
hugger or whatever, UM, then you really kind of have
to thank mosquitoes for sort of protecting these areas up
until modern times. That's definitely an interesting perspective. I definitely
(04:25):
wouldn't advocate getting rid of mosquitoes, nor could we ever
know and reasonably hope to do it. But I do
advocate you know, effective public health definitely, because especially when
we're creating situations through overpopulation or pour water, um you know,
storage management, etcetera, that encourages massive quantities and mosquitoes. So
(04:45):
let's talk about some of the likes and dislikes. What's
going on here? Who the people are getting all the bites. Yeah, well,
it's kind of like, you know, you're walking down the street,
you know, looking trying to figure out which restaurant you're
gonna hit. You know, it's like they're different cues that
are gonna stand out to you and and you may
help you make up your mind about where you gonna eat.
And it's similar to mosquitoes. Uh. The big one, of
(05:06):
course is c O two. Yeah, you know, which we're
constantly exciting and bigger people give off more c O two. Right,
This is not rocket science. Yeah, so they're going to
be drawn, they're going to be drawn into the larger people,
and a lot of times that generally breaks down to
two men as well. Um, you know, right, social preference
for an adult over child's or a man over women. Um.
(05:30):
I was reading an article about this that Anna Hunt
and I had O'Connor in the New York Times had
had posted, and he was saying that, yeah, um, it
had been positive that women were sweeter because of estrogen,
and thus mosquito's favorite them more. But the bigger size
and thus all that heat and c O two I
really get mosquitoes excited and you know, just biting. Yeah,
(05:51):
they there's they also think that that pregnant ladies may
also attract them more. And but it comes down of
the CEO two again, heavier breathing, right, And doubtless we're
gonna get a couple of listeners, small listeners out there
who swear that they're you know, the ones who attract
all the mosquitoes. And so size isn't the the end
all to be all nors c O two, A couple
(06:12):
other things factor in ship and and nobody knows the
exact formula for attracting that mosquito, like we can stress,
but we do know a couple of the factors, so
C two and and and again with CEO two. It's
like if you're if you're really active, maybe you really active,
little person. You know, you're out there jumping around. I
don't know you're you know, you're playing volleyball, shooting hoops.
(06:33):
You're active because they're just gonna notice you because you're
a small person talking with your hands, et cetera. Then
then yeah, you're you're producing more CEO two, and you're
you're likely to attract like, like, it's amazing how far
away they can they can sense you. They can they
can smell a meal like a hundred and sixty five
ft away. I'm not sure I could smell a meal
(06:53):
hundred sixty five ft away unless it was like barbecue,
you know, off a truck. You know, I was, I
was down the wind of it. Maybe, but right, And
when you think about they can cover up to a
mile or a mile and a half in an hour,
you know, they can cover some serious ground to get
to you if they want. And then okay, so let's
talk about smell. Yeah, are we wearing perfume? I assume
(07:13):
you're not read when they think it sounds like I
stink in here. No, no, I'm not saying that you stink.
But I did read one article that was talking, well
comment to an article, and this woman was swearing that
mosquitoes love Shalomar. What it's It's a ladies perfume. It's
kind of old school, but so are you wearing perfume?
(07:34):
This could attract it, and then less good smelling things
attract mosquitoes. But what's the perfect stinky combo? Um? Well,
it's sounding like from from what we've covered so far,
if you were a large, out of breath person who
moved your hands moves their hands, and then you're you're
probably pretty attract And if you really want to tip
the scales, start drinking a bunch of beer, because that's that.
(07:57):
That's because there's there are a lot of like weird
myths out there. I was actually at a thing last
night where there are a lot of mosquitoes around and
people I was asking people, It's like, hey, well, you
know we're doing this podcast tomorrow. What have you heard,
um actually like attract mosquitoes And like I heard bananas, Um,
if you bananas will attract mosquitoes. Um. See what were
some of the others um, garlic, garlic floats around there, yea,
(08:21):
the vitamin B twelve. Um, yeah, well so I was.
I was researching some of these because you brought these
to my attention, and I went on the American Mosquito
Control Association site. And so bear in mind the source,
the American Mosquito Control Association, They're bound to have some
industry interest. But um, they said that no, garlic, vitamin
(08:42):
B twelve, all those other systemics don't in fact prevent
the mosquitoes from biting, and the bananas don't necessarily attract
them either. My favorite fact from this particular website was
they mentioned that Limburger cheese has also been found to
be attractive to mosquitoes, and they took it one step farther.
They said that perhaps that attraction to limburger cheese was
(09:03):
because they resembled it resembled the smell of human feet. Okay,
so big person out of breath, talking with your hands,
drinking beer and then maybe eating limburger cheese or just
having really stinky feet. Also not sitting under a fan,
because if you're hanging out under a fan, uh, then
that's going to disperse like the CEO two, like you're
(09:23):
not just gonna be setting in like this big bubble
of CEO two funk. Yeah, and I have you know
often they say, you know, have a fan going because
they keeps them away from you know, the meal area,
you know, if you're having a picnic or whatever. So
so I guess it it works in that regard to stirs.
It stirs up the CEO two, keeps it from settling
in and just being a big bat signal for mosquitoes.
(09:47):
So let's get into uh an experiment that checked out
one of these factors, and uh it was alcohol in fact,
and it was. It was according to a paper published
in Plus one Pila p l Os one and back
in March two, I had a most excellent title. It's
aid beer consumption increases human attractiveness to malaria mosquitoes. Yeah,
(10:09):
so you can look at the paper if you guys want,
if you're so inclined. It reminds me of something that
might be in the what if the ignoble prizes. What's
that journal? Um improbable research? Yeah, this seems like a
title that could appear in probable research, But no, it
was not improbable. In fact, it was probable and it
was carried out in Burkina Faso, an area of Africa
that's caesar fair amount of malaria. So let's check out
(10:31):
what what happened with this experiment. Okay, Like most of
you guys listening, researchers noticed that malaria and alcohol consumption
represents some pretty big public health problems. So they decided
to investigate the links between the two. It seems like
a good idea, right, So here's what they did. And
it didn't involve getting a bunch of participants drunk and
(10:52):
letting them hang out with a bunch of bl blood
their sea mosquitoes. Yeah, because that's what I thought it
was going to be, you know, really cruel, kind of
like some of these other periments we've we've encountered where
like a scientists one bites some people over and they
think it's a cocktail party, but it's really a psychological experiment. No.
There there's a whole section in the paper devoted to ethics.
So these researchers took the ethical steps. So what they
(11:14):
did was they got forty three adult males between ages
twenty and forty three, and they're from of course, Burkina
Faso to participate in their study, so they randomly assigned
their their beer drinking participants too. This is the big
disappointment for somebody signed up to the beer group or
the water group, right, because you have to have a
control group. And the beer in question was a local
(11:37):
beer called Dolo and it's pretty lower, low content and
three percent alcohol content, and it's the most popular drink
in the region, so it makes sense to to test
it out with the most popular drink in the region.
And not just the beer, not just the participants. They
had to get some mosquitoes, right, and so they rounded
up some Naphilis Gambia mosquitoes that were present in the
(11:58):
villages for experiment and they read them in a lab
and they made sure that the females they are going
to use, because you guys know that females are the
mosquitoes that are biting, not the males. Yeah, that's that's
my thing. I don't really have any problem with the
male mosquitoes. It's the ladies that are awful. Here's the
ladies that are awful. And uh, I mean, why do
they why do they need the blood male? They got
babies to feed, right, Yeah, they got eggs to nourish too, yeah,
(12:22):
so so. So they got their female mosquitoes, they got
them good and hungry. And since they're not going to
be counting the mosquitoes on their participants, they had to
rely on something called an old factometer smell ascope kind
of a thing, a little bit. Uh, it's it's a
device that labs may use to disperse an odor precisely. Okay,
(12:42):
so not a smell. It's like a like a stink gun,
if you will, the smell gun and odor distributor. Is
there such thing as a stint gun? Are you just
totally making that up here? And I'm just trying to
like picture in my head. It's it shoots an odor, right,
it directs, it's directs an oder. So here's what they did.
(13:03):
They got their participants, the beer drinking ones and the
water drinking ones. They sat him in a tent. They
pointed a fan at the at the participants, and the
fan directed the body order towards the old factometer, and
they measured the attractiveness before giving them water a beer.
How are you going to measure somebody's attractiveness? It's not
Hey he's cute, Hey he's not. Oh that guy really
(13:23):
needs to do something with his eyebrows because you're trying
to appeal to a mosquito. And that just hasn't been
a lot of like the advertising industry hasn't really been
going after that demographic. They really really haven't. So they
measured attractiveness with the help of the old factometer. So
you have a bunch of mosquitoes sitting at the box
at the base of this Y shaped old factometer. So
(13:45):
do you have that kind of in your head. It's
at the the base of the tail of the y.
There's a box there, okay, and then you're gonna have
the stem of the y coming up and then it's
going to branch off into the two arms of the y. Okay,
see that? Okay. So at first they had these mosquitoes
kind of just sitting at this base box at the
tail of the y, and they defined attractiveness by how
(14:06):
many mosquitoes you induced to fly towards the yummy bottle
or smell so to fly toward the arms of the y. Right,
So they call that activating, how many mosquitoes you activated,
And they measured this um so they would blow the
odor of a beer drinking personal water drinking person how
many mosquitoes are any making fly toward the arms of
the way. It's kind of like a little like a
(14:27):
it's like a maze kind of right, I mean, not
really a maze, but it just the old road that
forks two ways. Which road are they going to take? Yeah,
the beer road or the water road? Right? It looks
like something out of the wasp factory. It's really really cool.
I think I saw a picture of it. It is
pretty neat. I didn't know such things existed. And it
seems like a pretty simple operation once you once you
(14:48):
think about it. So it wasn't just how many mosquitoes
you induced to fly. They had to pick the right
road that you were just talking about. So are they
going to orient toward the water one or the beer one?
And sure enough they found the researcher found that the
mosquitoes oriented towards the beer one. In fact, sixty percent
of them um flew upwind and chose the arm with
(15:08):
the beery odor. So mosquitoes like beer. No surprise there.
So so what's the big deal here? You're only gonna
be able to fight malaria or or other insect born
diseases if you know who who's at risk in Verkina Faso,
the dolo drinking ones. Maybe so if you have knowledge
of this risk factor and then you can help public
health officials devise effective interventions. Yea. The thing that really
(15:32):
interested me about all this is that you kind of
had this or at least that kind of I find
myself having this sort of mindset works like mosquitoes are
just gonna bite everybody, and there's not really any rhyme
or reason to it, unless unless you're wearing you know,
some sort of off or something on you, or you know,
or head to toe in garments. But but it's really
kind of it's more like a like a predator, like
(15:53):
in like in the Serengetti, like prowling. You know that
you see me to see any of the like anytime
you watch like a planet or their life, and you
see like a cheetah stalking something, It's like, like, what
did the predators always go after? That always go after
like the animal that can catch something weak, something something
you know, maybe it's a wounded animal, an old one,
the one that's not going to run it's fast, So
(16:14):
you're a mosquito. You're kind of doing the same thing.
You want to go after that the large because you
want a good meal out of it, like the large,
slow drunk guy exactly. Yeah, that that like that short
person who hasn't had anything to drink. Like, that's the
short person who's like smashing the you know what are
(16:36):
those things on the badminton that shuttle cocks. I don't
know who's you know, doing the outdoor sports and he's
moving all around, well around, they might get winded, and
then you've got a winded person. They're not gonna so
so it's that it's that I think it's that that small,
still person who hasn't had anything to drink and doesn't
(16:59):
smell funny. It's like going next to them and trying
to get a meal off of that neck. You're gonna
get squatted, right right. Yeah, So all these cues correlate
on an evolutionary level with how well a host is
able to defend itself and the people that are less
able to defend themselves. Yeah, mosquitoes are going off to them.
And unfortunately that means if you're large, or pregnant or
some other combination of those factors. It brings to mind,
(17:21):
you know, as people are always throwing outdoor events and
you want you want to prevent you know, mosquitoes from
coming after people. What if like some entrepreneur out there
started hiring themselves out as a mosquito bait like they're
they're they're all duals, Like, look, I will show up
at your party and I will drink a lot of
beer and run around in circles and and the mosquitoes
are gonna come after me, and you guys can just
(17:42):
do what you want, carry on, have a good time
and just you know, ignore me. Right. It would be
like cit chanella, but way more effective and entertaining. Exactly. Yeah,
so we'd like to hear how you guys we add
on the scale? Are you do mosquitoes love you? Do
they stay away from me? Like the plague? Do you
let us know? Send us Aknee mel A's science stuff
at host works dot com And we sure do get
(18:03):
email at science stuff at how stuff rooks dot com.
In fact, that so you got two in your hand
right now? Do you want to read this? I'm sorry,
I was just waiting for the listener and mail sound
effect to give an ample space. That's a pretty cool
effect that we gotta like it. Yeah, okay, I think
that was a good enough foss um. So we got
(18:24):
some email from momm and it looks like, well, no,
that's her email name. Her real name is Gretchen gretchen N,
and Gretchen N used to work for the City of
Chicago's Department of Environment and she worked on it while
the rooftop garden was being planned and built on the
City Hall. So that's pretty cool. So she really had
some inside scoop on the Chicago green roof stop that
(18:46):
we were talking about that podcast. Gretchen, however, proposed an
interesting idea, and she was saying that if you can't
put a green roof on your house, there are other alternatives.
She writes, When my husband and I rehapped our house,
we need that we wanted a greener roof, so we
chose a standing same metal roof, being metal and naturally
reflects solar energy back into space, and we included a
special coating to increase the albedo. The color of the
(19:09):
roof is champagne. Doesn't that sound nice? Is the champagne
colored roof? A champagne colored metal roof has the reflectivity
of a point four five and an emissivity of point
seven eight, And of course She's found that her A
C cost have dropped significantly and the upstairs is far
more comfortable. That's cool. Yeah, pretty cool, Aggrettion. And she
also wrote that the biggest problem she had when she
(19:32):
was getting the green roof together was finding builders to
take her seriously. She hadn't been insistent about wanting this
roof and educating the builder, she probably would have wound
up with asphalts shingles. So go, Gretchen, sticking to your
green guns. Yeah. We also heard it from a couple
of you guys on our smart grid podcast, and uh
one was from Sean, who goes by the nickname Speedy.
I love that. And Sean ran in to tell us
(19:55):
that he in fact works in the electric utility field
for a company that develops outage man aagement and smartcarde software.
So this is the guy to go to with questions. Sean,
where were you when we're developing this podcast? And uh,
I was wondering during the podcast, I don't know if
you guys remember if businesses would be okay with electricity
demand pricing. Remember we were talking about that, speculating, you know,
(20:16):
about whether we drive up costs and teleworking and different measures.
Um so he Sean writes that, yeah, I can confirm
that today companies will shift their operations to different times
or turn off various systems to save money. In exchange,
they get a discounted rate for all the power usage
from the utilities. And he also writes that which utilities
(20:37):
find is that when consumers are given the choice and information,
they will better use power. Excellent. This kind of ties
into a blog post I want to do about persuasive technology. Well,
it's it's also reminds me of you know that the
little UH displays they put up on the side of
the road to tell you what speed you're going, and
it starts flashing at you if you're a little over this,
if you're at or over the speed limit, and they
(20:58):
say those actually are pretty effective, you know, because it's
kind of it gives you the information and you just
kind of like sometimes I think, just subconsciously start regulating it.
But if you had you know, an actual dollar sign
tied up in it, you know even more so. Um.
And then we had I heard from a guy named
John who written with some smart code comments and Seohn
specifically had an idea for fighting vampire energy. What he
(21:20):
wants to do is he wants to make an app
on the iPhone that can control the electric switches in
the house while connected to your WiFi, and so the
WiFi is constantly on. And the big selling point of
the application, he writes, is instead of just a master switches,
that software is programmable, so you could program certain switches,
start off with the command on the phone, and you
know program and no one is home this way, so
(21:42):
you know, you wouldn't wind up cutting the power to
your alarm clock because you gotta have your alarm clock
on all the time, right. Yeah, So that's pretty cool
as long as I could figure out the iPhone app. Yeah,
some of them are designed a little weird. Yeah, and
I guess I would have to have an iPhone too, Yeah,
and allow smunt. Just Bram from Canada writes he lives
(22:04):
in Manitoba, Canada, and he was saying he was struck
by a comment made about why the energy utilities are
encouraging efficiency and reduced consumption of electricity at the consumer level.
Uh So, he he lives in Manitoba and it's a
net exporter of electricity. So those guys make extensive use
of hydro electric power to generate electricity and with a
relatively small population, we're able to sell electricity to neighboring
(22:25):
provinces and states. Right, so the incentive there is built
in for for bram and as a fellow folks in Manitoba.
So it's pretty interesting. I did like hearing a lot
about how people are experiencing you know, smart good and
smarket technology, just because it is sort of a new concept. Yeah.
The great thing about especially the feedback is the smart
god is something that's happened, that's in the process of happening,
(22:49):
and it's happening at various levels, you know, from again
from the user level to the power generation level and
every step in between. And so we got to hear
from you know, a few different people, um, you know,
along that that long line of distribution. Yeah, so again,
we always love to hear from you. So send us
an email at scien Stuff at how stuff first dot
com or you can go to the site too. Yeah,
(23:10):
check out, check us out. We're on Facebook, uh stuff
in the Science Lab and we're on Twitter as lab stuff,
and we'll keep that updated, uh, you know, pretty much
daily with our latest articles, latest blog post and the
latest podcast topics. All right, thanks for listening. For more
(23:34):
on this and thousands of other topics because it how
stuff works dot Com. Want more how stuff works, check
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home page
Welcome to Stuff from the Science Lab from how stuff
Works dot com. Hey guys, welcome to the podcast. This
is Alice and I don't know like the science editor
how stuff works dot com. And this is Robert Lamb,
science writer's how stuff Works dot com. And we are
(00:23):
podcasting to you from the Georgia summer means and mosquito. Yes,
lots of mosquitoes, So let's talk about the obvious question
out there. Do you mosquitoes flocked towards you? That seems
to be like, like, anytime I'm in an outdoor event
like that and someone gets bit in my mosquito, that's
like the instant conversation topic because someone's always like, I'm
(00:44):
mosky debate or they'll be like, normally I get bitten
by mosquitoes and my husband doesn't, or you know, it's
vice versa. I mean, it's something we all have some
experience with. I don't think any of us have necessarily
figured it out. So I had my Emma staying with
us a few weeks ago, and my mother in law
happens to be one of the people who she says,
(01:04):
mosquitoes flack to and she gets a lot of bites
and no kidding. She went up to um sort of
this loft spare room area that we have a whole
bunch of our stuff in and also our lovely guests
get to stand. And actually, no, that's the point. I mean,
nothing's really, nobody's really ever up there. You know, we
never go up there. There's a fan going, you know,
(01:25):
so maybe the fan would deflect mosquitoes. But she went
up there and within minutes she was bitten five times.
I felt bad, I felt terrible. I felt like she lived,
you know, she thought we lived in some you know,
mosquito ridden hobble. But I think they really do like her. Wow.
And and that comes down to the interesting question do
mosquitoes really like some people more than others or is
(01:47):
this just kind of um, you know barbecue hearsay, Well,
you can you can count on science to get to
the bottom of some of these mysteries. So we did
a little digging, and as it turns out, they really
do exhibit a preference for certain folks. So there was
a In Chee thousand one, a guy by the name
of David W. Kelly published a paper in Trends in Parasitology,
and it was called, appropriately enough, why are some people
(02:10):
bitten more than others the scientists and their titles. That
was a pretty good one. Um. In this case, Kelly
says humans will get bitten by blood sucking insects, and
frequently all of us are going to get a bite, right,
nobody's immune to it, but a special subset of that
population will be quote unquote heavily attacked. Okay, so let's
(02:30):
quantify the numbers that that Kelly starts stirring around in
this paper. So put ten people in a room with
say some anopolies mosquitoes, and those are the notorious specters
for the malarial parasite plasmodium, and or two of those
people in that room are going to be responsible for
passing on eight of the disease. Okay, so let's let's
talk about it again. Two people are going to pass
(02:52):
on eight of the disease according to a Woolhouse at all.
So if that's pretty crazy and so, I mean, that
does seem to point or the idea that, yes, in fact,
mosquitoes do exhibit a preference from a public health perspective.
Imagine if you could really home in on that and
figure out what makes them so attractive. I mean, not
only would you know mosquitoes or companies interested in mosquito
(03:15):
control will be hugely interested in this, but the rest
of us would want to hang out with them, like
their mosquitoes everywhere. Call up, Charlie, I want him standing
next to me, right and you know, mosquito bits are
annoying and we're kind of kidding at it, but you know,
when you think about all those people dying from malaria
or other mosquito born diseases, really stinks. Well, this is interesting, um.
(03:37):
And this is a slight tangent here, but I ran
across a really cool argument for mosquitoes, because mosquitoes are
one of the things you're frequently here, like why do
we have mosquitoes? Like if you know, if if there's
a god in heaven wanted he create mosquitoes, that kind
of thing. Um. But one one interesting argument for them
is that mosquitoes and their malaria have kept humans out
(04:01):
of certain areas of the world for long periods of time,
or at least kept them from expanding into those areas
in large numbers. So the argument is that if you're
you know, um, an environmentalist or you know a tree
hugger or whatever, UM, then you really kind of have
to thank mosquitoes for sort of protecting these areas up
until modern times. That's definitely an interesting perspective. I definitely
(04:25):
wouldn't advocate getting rid of mosquitoes, nor could we ever
know and reasonably hope to do it. But I do
advocate you know, effective public health definitely, because especially when
we're creating situations through overpopulation or pour water, um you know,
storage management, etcetera, that encourages massive quantities and mosquitoes. So
(04:45):
let's talk about some of the likes and dislikes. What's
going on here? Who the people are getting all the bites. Yeah, well,
it's kind of like, you know, you're walking down the street,
you know, looking trying to figure out which restaurant you're
gonna hit. You know, it's like they're different cues that
are gonna stand out to you and and you may
help you make up your mind about where you gonna eat.
And it's similar to mosquitoes. Uh. The big one, of
(05:06):
course is c O two. Yeah, you know, which we're
constantly exciting and bigger people give off more c O two. Right,
This is not rocket science. Yeah, so they're going to
be drawn, they're going to be drawn into the larger people,
and a lot of times that generally breaks down to
two men as well. Um, you know, right, social preference
for an adult over child's or a man over women. Um.
(05:30):
I was reading an article about this that Anna Hunt
and I had O'Connor in the New York Times had
had posted, and he was saying that, yeah, um, it
had been positive that women were sweeter because of estrogen,
and thus mosquito's favorite them more. But the bigger size
and thus all that heat and c O two I
really get mosquitoes excited and you know, just biting. Yeah,
(05:51):
they there's they also think that that pregnant ladies may
also attract them more. And but it comes down of
the CEO two again, heavier breathing, right, And doubtless we're
gonna get a couple of listeners, small listeners out there
who swear that they're you know, the ones who attract
all the mosquitoes. And so size isn't the the end
all to be all nors c O two, A couple
(06:12):
other things factor in ship and and nobody knows the
exact formula for attracting that mosquito, like we can stress,
but we do know a couple of the factors, so
C two and and and again with CEO two. It's
like if you're if you're really active, maybe you really active,
little person. You know, you're out there jumping around. I
don't know you're you know, you're playing volleyball, shooting hoops.
(06:33):
You're active because they're just gonna notice you because you're
a small person talking with your hands, et cetera. Then
then yeah, you're you're producing more CEO two, and you're
you're likely to attract like, like, it's amazing how far
away they can they can sense you. They can they
can smell a meal like a hundred and sixty five
ft away. I'm not sure I could smell a meal
(06:53):
hundred sixty five ft away unless it was like barbecue,
you know, off a truck. You know, I was, I
was down the wind of it. Maybe, but right, And
when you think about they can cover up to a
mile or a mile and a half in an hour,
you know, they can cover some serious ground to get
to you if they want. And then okay, so let's
talk about smell. Yeah, are we wearing perfume? I assume
(07:13):
you're not read when they think it sounds like I
stink in here. No, no, I'm not saying that you stink.
But I did read one article that was talking, well
comment to an article, and this woman was swearing that
mosquitoes love Shalomar. What it's It's a ladies perfume. It's
kind of old school, but so are you wearing perfume?
(07:34):
This could attract it, and then less good smelling things
attract mosquitoes. But what's the perfect stinky combo? Um? Well,
it's sounding like from from what we've covered so far,
if you were a large, out of breath person who
moved your hands moves their hands, and then you're you're
probably pretty attract And if you really want to tip
the scales, start drinking a bunch of beer, because that's that.
(07:57):
That's because there's there are a lot of like weird
myths out there. I was actually at a thing last
night where there are a lot of mosquitoes around and
people I was asking people, It's like, hey, well, you
know we're doing this podcast tomorrow. What have you heard,
um actually like attract mosquitoes And like I heard bananas, Um,
if you bananas will attract mosquitoes. Um. See what were
some of the others um, garlic, garlic floats around there, yea,
(08:21):
the vitamin B twelve. Um, yeah, well so I was.
I was researching some of these because you brought these
to my attention, and I went on the American Mosquito
Control Association site. And so bear in mind the source,
the American Mosquito Control Association, They're bound to have some
industry interest. But um, they said that no, garlic, vitamin
(08:42):
B twelve, all those other systemics don't in fact prevent
the mosquitoes from biting, and the bananas don't necessarily attract
them either. My favorite fact from this particular website was
they mentioned that Limburger cheese has also been found to
be attractive to mosquitoes, and they took it one step farther.
They said that perhaps that attraction to limburger cheese was
(09:03):
because they resembled it resembled the smell of human feet. Okay,
so big person out of breath, talking with your hands,
drinking beer and then maybe eating limburger cheese or just
having really stinky feet. Also not sitting under a fan,
because if you're hanging out under a fan, uh, then
that's going to disperse like the CEO two, like you're
(09:23):
not just gonna be setting in like this big bubble
of CEO two funk. Yeah, and I have you know
often they say, you know, have a fan going because
they keeps them away from you know, the meal area,
you know, if you're having a picnic or whatever. So
so I guess it it works in that regard to stirs.
It stirs up the CEO two, keeps it from settling
in and just being a big bat signal for mosquitoes.
(09:47):
So let's get into uh an experiment that checked out
one of these factors, and uh it was alcohol in fact,
and it was. It was according to a paper published
in Plus one Pila p l Os one and back
in March two, I had a most excellent title. It's
aid beer consumption increases human attractiveness to malaria mosquitoes. Yeah,
(10:09):
so you can look at the paper if you guys want,
if you're so inclined. It reminds me of something that
might be in the what if the ignoble prizes. What's
that journal? Um improbable research? Yeah, this seems like a
title that could appear in probable research, But no, it
was not improbable. In fact, it was probable and it
was carried out in Burkina Faso, an area of Africa
that's caesar fair amount of malaria. So let's check out
(10:31):
what what happened with this experiment. Okay, Like most of
you guys listening, researchers noticed that malaria and alcohol consumption
represents some pretty big public health problems. So they decided
to investigate the links between the two. It seems like
a good idea, right, So here's what they did. And
it didn't involve getting a bunch of participants drunk and
(10:52):
letting them hang out with a bunch of bl blood
their sea mosquitoes. Yeah, because that's what I thought it
was going to be, you know, really cruel, kind of
like some of these other periments we've we've encountered where
like a scientists one bites some people over and they
think it's a cocktail party, but it's really a psychological experiment. No.
There there's a whole section in the paper devoted to ethics.
So these researchers took the ethical steps. So what they
(11:14):
did was they got forty three adult males between ages
twenty and forty three, and they're from of course, Burkina
Faso to participate in their study, so they randomly assigned
their their beer drinking participants too. This is the big
disappointment for somebody signed up to the beer group or
the water group, right, because you have to have a
control group. And the beer in question was a local
(11:37):
beer called Dolo and it's pretty lower, low content and
three percent alcohol content, and it's the most popular drink
in the region, so it makes sense to to test
it out with the most popular drink in the region.
And not just the beer, not just the participants. They
had to get some mosquitoes, right, and so they rounded
up some Naphilis Gambia mosquitoes that were present in the
(11:58):
villages for experiment and they read them in a lab
and they made sure that the females they are going
to use, because you guys know that females are the
mosquitoes that are biting, not the males. Yeah, that's that's
my thing. I don't really have any problem with the
male mosquitoes. It's the ladies that are awful. Here's the
ladies that are awful. And uh, I mean, why do
they why do they need the blood male? They got
babies to feed, right, Yeah, they got eggs to nourish too, yeah,
(12:22):
so so. So they got their female mosquitoes, they got
them good and hungry. And since they're not going to
be counting the mosquitoes on their participants, they had to
rely on something called an old factometer smell ascope kind
of a thing, a little bit. Uh, it's it's a
device that labs may use to disperse an odor precisely. Okay,
(12:42):
so not a smell. It's like a like a stink gun,
if you will, the smell gun and odor distributor. Is
there such thing as a stint gun? Are you just
totally making that up here? And I'm just trying to
like picture in my head. It's it shoots an odor, right,
it directs, it's directs an oder. So here's what they did.
(13:03):
They got their participants, the beer drinking ones and the
water drinking ones. They sat him in a tent. They
pointed a fan at the at the participants, and the
fan directed the body order towards the old factometer, and
they measured the attractiveness before giving them water a beer.
How are you going to measure somebody's attractiveness? It's not
Hey he's cute, Hey he's not. Oh that guy really
(13:23):
needs to do something with his eyebrows because you're trying
to appeal to a mosquito. And that just hasn't been
a lot of like the advertising industry hasn't really been
going after that demographic. They really really haven't. So they
measured attractiveness with the help of the old factometer. So
you have a bunch of mosquitoes sitting at the box
at the base of this Y shaped old factometer. So
(13:45):
do you have that kind of in your head. It's
at the the base of the tail of the y.
There's a box there, okay, and then you're gonna have
the stem of the y coming up and then it's
going to branch off into the two arms of the y. Okay,
see that? Okay. So at first they had these mosquitoes
kind of just sitting at this base box at the
tail of the y, and they defined attractiveness by how
(14:06):
many mosquitoes you induced to fly towards the yummy bottle
or smell so to fly toward the arms of the y. Right,
So they call that activating, how many mosquitoes you activated,
And they measured this um so they would blow the
odor of a beer drinking personal water drinking person how
many mosquitoes are any making fly toward the arms of
the way. It's kind of like a little like a
(14:27):
it's like a maze kind of right, I mean, not
really a maze, but it just the old road that
forks two ways. Which road are they going to take? Yeah,
the beer road or the water road? Right? It looks
like something out of the wasp factory. It's really really cool.
I think I saw a picture of it. It is
pretty neat. I didn't know such things existed. And it
seems like a pretty simple operation once you once you
(14:48):
think about it. So it wasn't just how many mosquitoes
you induced to fly. They had to pick the right
road that you were just talking about. So are they
going to orient toward the water one or the beer one?
And sure enough they found the researcher found that the
mosquitoes oriented towards the beer one. In fact, sixty percent
of them um flew upwind and chose the arm with
(15:08):
the beery odor. So mosquitoes like beer. No surprise there.
So so what's the big deal here? You're only gonna
be able to fight malaria or or other insect born
diseases if you know who who's at risk in Verkina Faso,
the dolo drinking ones. Maybe so if you have knowledge
of this risk factor and then you can help public
health officials devise effective interventions. Yea. The thing that really
(15:32):
interested me about all this is that you kind of
had this or at least that kind of I find
myself having this sort of mindset works like mosquitoes are
just gonna bite everybody, and there's not really any rhyme
or reason to it, unless unless you're wearing you know,
some sort of off or something on you, or you know,
or head to toe in garments. But but it's really
kind of it's more like a like a predator, like
(15:53):
in like in the Serengetti, like prowling. You know that
you see me to see any of the like anytime
you watch like a planet or their life, and you
see like a cheetah stalking something, It's like, like, what
did the predators always go after? That always go after
like the animal that can catch something weak, something something
you know, maybe it's a wounded animal, an old one,
the one that's not going to run it's fast, So
(16:14):
you're a mosquito. You're kind of doing the same thing.
You want to go after that the large because you
want a good meal out of it, like the large,
slow drunk guy exactly. Yeah, that that like that short
person who hasn't had anything to drink. Like, that's the
short person who's like smashing the you know what are
(16:36):
those things on the badminton that shuttle cocks. I don't
know who's you know, doing the outdoor sports and he's
moving all around, well around, they might get winded, and
then you've got a winded person. They're not gonna so
so it's that it's that I think it's that that small,
still person who hasn't had anything to drink and doesn't
(16:59):
smell funny. It's like going next to them and trying
to get a meal off of that neck. You're gonna
get squatted, right right. Yeah, So all these cues correlate
on an evolutionary level with how well a host is
able to defend itself and the people that are less
able to defend themselves. Yeah, mosquitoes are going off to them.
And unfortunately that means if you're large, or pregnant or
some other combination of those factors. It brings to mind,
(17:21):
you know, as people are always throwing outdoor events and
you want you want to prevent you know, mosquitoes from
coming after people. What if like some entrepreneur out there
started hiring themselves out as a mosquito bait like they're
they're they're all duals, Like, look, I will show up
at your party and I will drink a lot of
beer and run around in circles and and the mosquitoes
are gonna come after me, and you guys can just
(17:42):
do what you want, carry on, have a good time
and just you know, ignore me. Right. It would be
like cit chanella, but way more effective and entertaining. Exactly. Yeah,
so we'd like to hear how you guys we add
on the scale? Are you do mosquitoes love you? Do
they stay away from me? Like the plague? Do you
let us know? Send us Aknee mel A's science stuff
at host works dot com And we sure do get
(18:03):
email at science stuff at how stuff rooks dot com.
In fact, that so you got two in your hand
right now? Do you want to read this? I'm sorry,
I was just waiting for the listener and mail sound
effect to give an ample space. That's a pretty cool
effect that we gotta like it. Yeah, okay, I think
that was a good enough foss um. So we got
(18:24):
some email from momm and it looks like, well, no,
that's her email name. Her real name is Gretchen gretchen N,
and Gretchen N used to work for the City of
Chicago's Department of Environment and she worked on it while
the rooftop garden was being planned and built on the
City Hall. So that's pretty cool. So she really had
some inside scoop on the Chicago green roof stop that
(18:46):
we were talking about that podcast. Gretchen, however, proposed an
interesting idea, and she was saying that if you can't
put a green roof on your house, there are other alternatives.
She writes, When my husband and I rehapped our house,
we need that we wanted a greener roof, so we
chose a standing same metal roof, being metal and naturally
reflects solar energy back into space, and we included a
special coating to increase the albedo. The color of the
(19:09):
roof is champagne. Doesn't that sound nice? Is the champagne
colored roof? A champagne colored metal roof has the reflectivity
of a point four five and an emissivity of point
seven eight, And of course She's found that her A
C cost have dropped significantly and the upstairs is far
more comfortable. That's cool. Yeah, pretty cool, Aggrettion. And she
also wrote that the biggest problem she had when she
(19:32):
was getting the green roof together was finding builders to
take her seriously. She hadn't been insistent about wanting this
roof and educating the builder, she probably would have wound
up with asphalts shingles. So go, Gretchen, sticking to your
green guns. Yeah. We also heard it from a couple
of you guys on our smart grid podcast, and uh
one was from Sean, who goes by the nickname Speedy.
I love that. And Sean ran in to tell us
(19:55):
that he in fact works in the electric utility field
for a company that develops outage man aagement and smartcarde software.
So this is the guy to go to with questions. Sean,
where were you when we're developing this podcast? And uh,
I was wondering during the podcast, I don't know if
you guys remember if businesses would be okay with electricity
demand pricing. Remember we were talking about that, speculating, you know,
(20:16):
about whether we drive up costs and teleworking and different measures.
Um so he Sean writes that, yeah, I can confirm
that today companies will shift their operations to different times
or turn off various systems to save money. In exchange,
they get a discounted rate for all the power usage
from the utilities. And he also writes that which utilities
(20:37):
find is that when consumers are given the choice and information,
they will better use power. Excellent. This kind of ties
into a blog post I want to do about persuasive technology. Well,
it's it's also reminds me of you know that the
little UH displays they put up on the side of
the road to tell you what speed you're going, and
it starts flashing at you if you're a little over this,
if you're at or over the speed limit, and they
(20:58):
say those actually are pretty effective, you know, because it's
kind of it gives you the information and you just
kind of like sometimes I think, just subconsciously start regulating it.
But if you had you know, an actual dollar sign
tied up in it, you know even more so. Um.
And then we had I heard from a guy named
John who written with some smart code comments and Seohn
specifically had an idea for fighting vampire energy. What he
(21:20):
wants to do is he wants to make an app
on the iPhone that can control the electric switches in
the house while connected to your WiFi, and so the
WiFi is constantly on. And the big selling point of
the application, he writes, is instead of just a master switches,
that software is programmable, so you could program certain switches,
start off with the command on the phone, and you
know program and no one is home this way, so
(21:42):
you know, you wouldn't wind up cutting the power to
your alarm clock because you gotta have your alarm clock
on all the time, right. Yeah, So that's pretty cool
as long as I could figure out the iPhone app. Yeah,
some of them are designed a little weird. Yeah, and
I guess I would have to have an iPhone too, Yeah,
and allow smunt. Just Bram from Canada writes he lives
(22:04):
in Manitoba, Canada, and he was saying he was struck
by a comment made about why the energy utilities are
encouraging efficiency and reduced consumption of electricity at the consumer level.
Uh So, he he lives in Manitoba and it's a
net exporter of electricity. So those guys make extensive use
of hydro electric power to generate electricity and with a
relatively small population, we're able to sell electricity to neighboring
(22:25):
provinces and states. Right, so the incentive there is built
in for for bram and as a fellow folks in Manitoba.
So it's pretty interesting. I did like hearing a lot
about how people are experiencing you know, smart good and
smarket technology, just because it is sort of a new concept. Yeah.
The great thing about especially the feedback is the smart
god is something that's happened, that's in the process of happening,
(22:49):
and it's happening at various levels, you know, from again
from the user level to the power generation level and
every step in between. And so we got to hear
from you know, a few different people, um, you know,
along that that long line of distribution. Yeah, so again,
we always love to hear from you. So send us
an email at scien Stuff at how stuff first dot
com or you can go to the site too. Yeah,
(23:10):
check out, check us out. We're on Facebook, uh stuff
in the Science Lab and we're on Twitter as lab stuff,
and we'll keep that updated, uh, you know, pretty much
daily with our latest articles, latest blog post and the
latest podcast topics. All right, thanks for listening. For more
(23:34):
on this and thousands of other topics because it how
stuff works dot Com. Want more how stuff works, check
out our blogs on the house stuff works dot Com
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