The real reason why mosquitoes buzz

What does the love song of a mosquito sound like? Find out as our intrepid neuroscientists explore the meaning of all that annoying buzzing in your ear.

(Mosquito buzzing)

Greg Gage: We've all heard
the annoying sound of a mosquito,

and we will stop at nothing
to make it go away.

While this sound may be maddening to us,

perhaps it's music to a mosquito's ears.

The mosquito's nervous system has almost
as many sensory auditory cells as we do.

But why would they have
so many in such a small body,

and why would they need to be
so sensitive to sounds?

The answer is love.

[DIY Neuroscience]

(Music)

As humans, we do a lot
to attract each other.

Some things are conscious --

we put on makeup
and make sure we smell nice.

And some are unconscious.

You may unconsciously point your body
or even sit closer to someone you like.

These are courtship behaviors,
and a lot of animals have them.

And mosquitoes are no different.

So Haley's been spending her summer
bravely listening to mosquitoes,

and what she observed may surprise you.

So we want to investigate
how the mosquitoes make their song.

So Haley, how do we record
their wing beats?

Haley Smith: We need to tether them.

First, we anesthetize them
in a fridge or a bed of ice.

And then I transfer them
to this petri dish of ice,

just to get them even more anesthetized.

Next, I take an insect pin,

and what I do is put a tiny little dab
of superglue on this pin.

I want to make sure that I get it
on his thorax above his wings

so that when he is suspended,
his wings are still free to move.

So here's one down.

It's really hard to catch
male mosquitoes in the wild

because females are the only mosquitoes
that are attracted to humans.

They feed on human blood.

And now, we can try to get
some recordings from them.

So this is the stand
that I use to hold them.

I like to place it
right over the microphone

so that I can get a recording
of the buzzing that you hear.

That sound is generated
by how fast they're beating their wings.

This is a male.

The males have very bushy antennae,
and they look kind of feathery.

And they are also much smaller.

GG: So he's flying at around 600 hertz.

Can we try a female mosquito?

HS: Sure, here we go.

(Mosquito buzzing, lower pitch)

GG: Wow.

HS: This is a much lower
frequency than the male.

GG: Yeah, it sounds completely different.

(Mosquito buzzing)

(Mosquito buzzing, lower pitch)

So is it because they're
two different mosquitoes,

or because they're male and female?

HS: It's because
they're male and female.

GG: Alright, let's verify that.

Can you bring in another female
and see if she sounds

like mosquito A or mosquito B?

HS: Yeah.

(Mosquito buzzing, lower pitch)

And again, she is much lower
than the male.

GG: Yeah, she sounds different.

(Mosquito buzzing, lower pitch)

Yeah, she's spot-on 400.

HS: She really is.
GG: That's really bizarre.

HS: The females are at a much
lower pitch. They were around 400 hertz.

HS: And all of the females
were around that, too.

They were much larger than the males,

so they didn't have to flap their wings
as fast to stay in free flight.

GG: So they have larger wings,
so they're flapping slower.

And you noticed that all the females
have the same frequency, roughly?

And the males do, too.
That's kind of interesting.

So that must mean something.

Well, let's see what happens when
we put the male and the female together.

(Mosquitoes buzzing; pitch varies)

HS: When I put them
into the same hearing range,

I noticed that they were kind of
changing their tones.

It was kind of more dull, almost.

(Mosquitoes buzzing)

And when I put it back in my spectrogram
to see their interaction,

they were meeting at the same tone.

GG: OK, pause.

The males and females are singing a duet,

meaning that they adjust their wings
to be able to produce a common tone.

You have the male singing up here at G,

and you have the female
singing down here at D,

and when they get together,

you're saying that they change
the frequency of their wings

such that they come together?

HS: Yeah, exactly.
GG: And they sort of sing a duet.

(Mosquitoes gradually
adjusting to identical pitch)

HS: They're communicating
to let each other know

that they've basically
found a potential mate.

GG: So in other words,

the female tends to choose
a male that best sings her duet.

And studies have found
that if she's pregnant,

she doesn't even bother.

So if we can understand
the mosquito mating behavior,

we may be able to disrupt it in the wild
and prevent diseases like malaria.

But for now, the next time
you hear a mosquito buzzing,

just pause and remember she may be in love

and she may be singing her song,

looking for her perfect match.

(Mosquito buzzing)

(Smack)