Mosquito feeding
Mosquito feeding
Courtesy of the CDC

It’s summer and our ankles are covered in mosquito bites. So we want to know: How and why do mosquitoes suck our blood? Why do their bites itch ALL the time? Why do some people get bitten more than others? And do these pesky and possibly dangerous insects serve any kind of useful purpose?

Listen to this episode to learn more about “the most dangerous animal on the planet.”

And check out this video for an up-close look at the blood-sucking process:

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Audio Transcript

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[MUSIC PLAYING] MOLLY BLOOM: You're listening to Brains On from MPR News in Southern California Public Radio. We're serious about being curious.


Do you hear that? Never mind. I'm Molly--


OK, wait. There's definitely a bug in here. Shoo. OK, where was I? Oh yeah. I'm Molly Bloom, and today, we're going to talk about--



MOSQUITO: Wait, don't slap!

MOLLY BLOOM: What the what? A talking mosquito?

MOSQUITO: Hey, when you hang around a recording studio long enough, you pick up a few things.


MOSQUITO: I'm a huge fan of podcasts. I've been trying to work my way in here for days.

MOLLY BLOOM: Welcome, I guess? Hey, as long as you're here, maybe you could help me answer this question that was sent to us from Provo, Utah.

COLIN: Hello. I am Colin. My question is, how do mosquitoes suck out your blood?

MOSQUITO: Great question, Colin.

MOLLY BLOOM: That's usually my line.

MOSQUITO: Well, take a look at these mouthparts here.

MOLLY BLOOM: You'll have to describe them. This as a podcast.

MOSQUITO: Oh yeah! I'm a mosquito, and I'm here to show you my mouthparts.

MOLLY BLOOM: Tell, don't show.

MOSQUITO: Oh yeah. There are six different needle looking structures here that help me get my blood meal. These two, these ones that look like little saws, they're for piercing your skin. And these two, these ones hold the skin open so that I can stick this other needle into one of your blood vessels. That's the one that sucks up the blood. And then this last one injects some of my saliva into your blood.


MOSQUITO: It's not gross, it's useful. My spit does all sorts of amazing things to your blood chemistry. It keeps your blood from clotting and also opens your blood vessels wider. This helps me eat faster so I can get out there before you--


Squish me.

MOLLY BLOOM: I see. Well, here's a thought. How about maybe just not biting me? Your chance of getting squished would go way down.

MOSQUITO: Yeah, about that. See, I need the blood, actually. Only female mosquitoes bite because we need the protein and blood to make eggs and eventually, little baby mosquitoes. They're so cute. They look like little spiky dandelions.

MOLLY BLOOM: Sounds adorable?

MOSQUITO: You know, one has ever taken the time to chat with me. Thank you so much, Molly, for having me here today.

MOLLY BLOOM: This actually worked out really well. High five, mosquito.





MOLLY BLOOM: Before we answer more of your questions about mosquitoes, it's time for the mystery sound.


AUDIO TRACK: Mystery sound.

MOLLY BLOOM: Here it is.


Any guesses?

MARC SANCHEZ: There's definitely a water element going on.

MOLLY BLOOM: Oh, hi, Marc.


SANDEN TOTTEN: I think it's like a windstorm.

MOLLY BLOOM: Well, it's nice to see you, too, Sanden. And you guys are close, but not quite right. So we're going to get to the answer to the Mystery Sound in just a little bit. But first, you guys are here to talk about something else.

SANDEN TOTTEN: Well, yeah. You know, Molly, Marc and I, we love to spar, disagree over the big questions of the universe.

MARC SANCHEZ: Yeah, like which are cooler, bridges or tunnels?

SANDEN TOTTEN: Are cats evil, or are cats good?

MARC SANCHEZ: And Molly, we're feeling feisty again, and we want another debate.

SANDEN TOTTEN: But we're having trouble coming up with the perfect pairing. So we're asking all of you listening to send in yours. What are some cool things we can pit against each other?

MARC SANCHEZ: Purple versus green?

SANDEN TOTTEN: Feet versus hands.

MARC SANCHEZ: Grapes versus oranges?

SANDEN TOTTEN: Boxers versus briefs?

MOLLY BLOOM: Boxers and briefs? Yeah, you guys definitely need some help. So I know our Brains On listeners can come up with something way better. So let us know what you want Marc and Sanden to debate next. Write us at brainson@m-- as in Minnesota--

MARC SANCHEZ: Or hit us up on Facebook or look for us on Twitter or Instagram. We are @brains_on.

SANDEN TOTTEN: We'll pick our favorite matchup and do an episode all about it. So holler at us.


MOLLY BLOOM: Speaking of, it's time now to induct the latest group of Brains On Honor Rollees. These awesome people have sent us mail, drawn us pictures, given us questions and mystery sounds, and high fives. Here they are.


AUDIO TRACK: Brains Honor Roll. High five.

MOLLY BLOOM: Let's go back to the mystery sound. Here it is again.


I could listen to that all day. Any new guesses? Here with the answer is Farah and Kayvon from Berkeley, California.

FARAH: That was the sound of waves crashing at the beach in Kauai.

KAYVON: My favorite thing to do at the beach is go bodyboarding.

FARAH: And my favorite thing to do at the beach is sit on the shore and wait for the waves to rush over me.


MOLLY BLOOM: Now, back to your mosquito questions. Here's one I'm sure we all want to know.

SOPHIA: Hi, Brains On. My name is Sophia.

WILLIAM: My name is William. And our question is, why do mosquito bites itch?

MOLLY BLOOM: Now that our mosquito guest is no longer with us, we have a human mosquito expert who's agreed to help us.

LYRIC BARTHOLOMAY: Sure. My name is Lyric Bartholomay.

MOLLY BLOOM: She's a medical entomologist from the University of Wisconsin-Madison. Remember the mosquito saliva that we heard about earlier? That's the key to the itch.

LYRIC BARTHOLOMAY: The mosquitoes spit in you, and the body needs to respond somehow. There's actually a whole series of different proteins inside mosquito spit. The proteins in the saliva are causing your immune system to just go wild. Your body's recognizing that there's something there that wasn't supposed to be there.

MOLLY BLOOM: And you get an inflammatory response, which is that familiar itchy swelling and redness. Here's another question.

AMANDA: Hi, my name's Amanda.

ANASALI: Hi, my name's Anasali.

AMANDA AND ANASALI: And we're from McAllen, Texas.

AMANDA: We want to know why mosquitoes bite some people more than others.

LYRIC BARTHOLOMAY: I wish we knew. I always tell people that the reason they get bitten more than other people is because they're really delicious. So there are certain things that mosquitoes respond to when they're looking for somebody to feed on. Smells and sights. And some of the smells that they're attracted to are things like CO2, which, of course, we breathe out. And lactic acid, which is produced when we activate our muscles.

MOLLY BLOOM: Some studies have shown that people with O blood type or stinky feet attract more mosquitoes.

LYRIC BARTHOLOMAY: It's also probably important to point out that there are more than 3,000 different kinds of mosquitoes. And every one of those mosquitoes is responding to different chemical cues in the environment to find a host to feed on. So it's really hard to generalize.

MOLLY BLOOM: So yes, some mosquitoes are more attracted to O blood type, but not all. So how do we protect ourselves from mosquitoes?

LYRIC BARTHOLOMAY: There is one thing that you can do to really make a big difference in whether or not you get bitten. And that's to use a tried and true insect repellent. And so those insect repellents that have DEET in them, for example. There's all kinds of evidence to suggest that those work really, really well.

So mosquitoes respond to smells using their antennae and different organs on their body. And one of the theories is that if you have DEET on, the different organs on a mosquito that respond to smells are confused. So they can't smell you anymore.

MOLLY BLOOM: Another way the different species of mosquitoes vary is that only some of them carry the viruses and parasites that are harmful to humans.

LYRIC BARTHOLOMAY: For example, in the state of Iowa, with 55 different kinds of mosquitoes that we see, maybe about five of them are important in terms of disease transmission.

MOLLY BLOOM: But the ones that do carry disease cannot be ignored.

LYRIC BARTHOLOMAY: The mosquito that transmits malaria parasites in Africa is the most dangerous animal on the planet. By any measure. Because of the number of people that die after having been bitten by those mosquitoes.

MOLLY BLOOM: Which leads us to this question from Brian. He's from Sydney, Australia.

BRIAN: My question is, do mosquitoes have a purpose to be on the Earth? They go around annoying everybody. They suck your blood. So what are they meant for?

MOLLY BLOOM: Lyric says that even though mosquitoes are a nuisance and potentially dangerous, they do play an important role in the ecosystem.

LYRIC BARTHOLOMAY: The environment benefits from mosquitoes being there because mosquitoes feed all kinds of animals. You can find lots of mosquitoes in the bellies of ducks and frogs and all kinds of different animals. And so, they're a really essential part of the food chain. In places where we do a really good job of controlling mosquitoes and just take all of them out of the environment, it can have an impact on things like bird reproduction.

So a bird lays an egg, and she needs proper nourishment in order to lay healthy eggs, too. And so if she doesn't have all the mosquitoes to feed on, she might have brittle eggshells. Now I've told you that, but I've also told you that there's more than 3,000 kinds of mosquito.

MOLLY BLOOM: So Lyric says that instead of getting rid of all mosquitoes, scientists are working on ways to control the small number of mosquito species that spread disease and pathogens. One strategy involves injecting mosquitoes with a bacteria called Wolbachia. This bacteria is a natural one already living in some mosquitoes, just like all the bacteria we have living in our guts.

LYRIC BARTHOLOMAY: Wolbachia is really interesting. And what we've learned is that mosquitoes that are infected with Wolbachia are also not readily infected with other things. So it's a really powerful potential tool.

MOLLY BLOOM: So mosquitoes with this Wolbachia shouldn't be able to pick up and spread other diseases, making them a pest, but not deadly.

LYRIC BARTHOLOMAY: Sure, they're dangerous animals. But I think we should appreciate how a important they are. How can we appreciate the mosquitoes and understand their diversity and how they fit in an ecosystem, but also try and control the really dangerous ones for the benefit of people's health?


MOLLY BLOOM: That's it for this episode of Brains On. Brains On is produced by Marc Sanchez, Sanden Totten, and me, Molly Bloom. Many thanks to Nancy Ng for lending her vocal talents. If you have any questions or mystery sounds or drawings to share with us, you can email them to brainson@m-- as in Minnesota-- Or you can find our mailing address on our website, Thanks for listening.

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