This episode was written and produced by Leila Battison.

Why do bugs make the sounds they do? And how do they make them? In this episode, we explore the un-bee-lievable world of insect sounds, including crickets who craft tools to make themselves louder, and moths who can jam the natural sonar of bats. By the time it’s over, you’ll never hear these buzzes and chirps the same way again. Featuring entomologists Natasha Mhatre and Nancy Mioreli.

MUSIC FEATURED IN THIS EPISODE

Original music by Wesley Slover.
Unknown Phenomenon by Dream Cave
Mouse by Sound of Picture
Tricks and Treats by Raymond Grouse
The Story Begins by Hampus Naeselius
Game Hens by Confectionary
Right Beside Me by Cushy
Organisms by Sound of Picture
Dunder by Potions
Find My Place by Potions
Crumpet (With a Beat) by Confectionary
Occurrence by Martin Gauffin
Consumed by Darkness by Christoffer Moe Ditlevsen
Pop Vibration by Potions
Elka Park by Kyle McEvoy

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View Transcript ▶︎

You're listening to Twenty Thousand Hertz.

[music in]

[sfx: analog TV on]

News Reader: New details on a series of bizarre attacks. Dozens of unexplained illnesses.

[sfx: analog TV off]

Back in 2016, strange reports started coming out of the US embassy in Havana, Cuba.

News Reader: US diplomats based here in Havana said they began to experience these really strange symptoms, often at night, sometimes when they were in bed, asleep. The symptoms include hearing strange sounds, headaches, nausea, vertigo, confusion and a feeling of heat or pressure.

These illnesses came to be known as Havana Syndrome. The cause was unclear, but there was one common factor in many of these reports… a high-pitched buzzing or hissing sound.

News Reader: The sound is a common experience reported by dozens of Americans stricken overseas.

[music out]

Eventually, one of these diplomats captured a recording of this sound. And a quick disclaimer that listening to it won't hurt you, but it is pretty shrill and unpleasant, so we’ve turned it down a good bit. Here it is:

[sfx: Sonic weapon recording]

Leila Battison: There were all kinds of theories about what could be making this noise.

That's producer Leila Battison.

Leila Battison: Some guessed it was interference from electronic devices. Others said it could be a Russian sonic weapon. Intelligence experts speculated about a focused beam of microwaves fired into the homes of diplomats.

[sfx: pulsing beam]

But other scientists had a different explanation.

[music in]

Natasha Mhatre: Those are crickets.

Leila Battison: That's Natasha Mhatre, an expert in insect acoustics.

Natasha Mhatre: I've seen the data. It's pretty conclusive. Those are crickets. They're nothing else. They're really annoying, but they're just crickets.

[music out]

Leila Battison: Two scientists who analyzed that recording concluded that the species was most likely the Indies short-tailed cricket. Here's what they sound like.

[sfx: Indies Short-Tailed Cricket]

Leila Battison: And here's the recording captured by the diplomat.

[sfx: Sonic weapon recording]

Now, to be clear, we're not saying that this entire phenomenon can be explained by crickets. Because there's still a lot of debate about the cause of Havana Syndrome.

Leila Battison: But the idea that someone could mistake the buzz of crickets for a Russian sonic weapon isn't as strange as it might sound. Because large groups of insects can be shockingly intense.

[sfx: Ecuadorian cicadas]

Nancy Miorelli: When you're in it, it's loud.

Leila Battison: That's Nancy Miorelli.

Nancy Miorelli: I am an entomologist, which means that I study bugs.

Leila Battison: Nancy lives in Ecuador, which is home to plenty of noisy insects, like cicadas.

[sfx: single cicada]

Nancy Miorelli: I'll grab a male cicada cuz I like to open their wings and I like to show the structure that they're making the sounds with. And I literally have to shout over it because this one little bug is so loud. So it's amazing how loud they can get.

Leila Battison: Of course, not every insect can make that kind of racket.

Nancy Miorelli: There's specific groups that tend to make a lot of noise, like the katydids, crickets, and grasshoppers.

[music in]

Leila Battison: In large part, those noises are in fact, courting songs. To help two tiny insects find each other in the big wide world.

Nancy Miorelli: It's to say: "Hey, I'm here. Come find me. I'm really cute. I'm very loud. Listen to me."

Leila Battison: Normally, it's the guys who make all the noise.

Nancy Miorelli: Many times the female can't produce sound or doesn't produce sound. And if you think about it, it's because it's really risky, right? You're out there, you're on your little branch, on your little twig, and you are like, "Hey! Come mate with me! Over here!" Which obviously attracts literally every predator and their mother to the area.

Nancy Miorelli: Females don't want that, because once they've mated, they just want to go somewhere that's safe, find a safe spot to lay their eggs, and live their best life.

Leila Battison: But for the males, getting attention is worth the risk... At least, on an evolutionary level.

Nancy Miorelli: If your strategy is, "I'm gonna be really loud and I'm going to attract all the females," you can mate with ten females in a week and you die, you are ecologically, quote unquote “more fit” than a male who maybe lived for a month, but only mated twice.

[music out]

Leila Battison: Cicadas are a perfect example of this. Once they hatch, they climb onto the nearest perch and sing as loud as they possibly can.

[sfx: cicadas]

Nancy Miorelli: Only the males can buzz, so the females will respond by snapping her wings, so it'll make like a [sfx: snaps fingers] sound.

Nancy Miorelli: There's a great clip of David Attenborough. He finds one of those male cicadas that's buzzing and then he snaps his fingers, and makes the cicada follow him.

David Attenborough: I can imitate the female's wing flip with a snap of my fingers, and that causes them to follow me anywhere because they're so determined to find a female.

Leila Battison: But he soon gets more than he bargained for, as the insect flies right onto his head.

David Attenborough: Oh, the noise is awful...ohhh, quite right!

Leila Battison: As a group, cicadas are the loudest insects on the planet.

Nancy Miorelli: There are some cicadas that can buzz up to 120 decibels, which is like a jackhammer going off next to your window.

Leila Battison: Mating calls are important, but they aren't the only sounds that insects make. And these other noises tend to be less well understood.

Nancy Miorelli: A good example are bess beetles. If you pick them up, they'll squeak.

[sfx: squeaking bess beetle]

Nancy Miorelli: We think it's to scare predators, but they also seem to squeak with each other.

Leila Battison: Some beetles even talk to their kids.

Nancy Miorelli: There's the American burying beetle, they take care of their young. When the larva hatch, both the male and the female, the mom and the dad will make a variety of squeaky noises.

[sfx: squeaking burying beetle]

Nancy Miorelli: And we think it's some sort of communication, but we don't know exactly what they're communicating, but they are quite noisy down there.

Leila Battison: Queen bees also do something called piping.

[sfx: piping queen bee]

Nancy Miorelli: It's like a high pitch buzzing, whistling, almost.

Nancy Miorelli: And that happens when the colony gets too big and it's about to split.

Leila Battison: This piping sound is a battle cry, signaling that the queen is ready to fight to the death with any other queens in the hive.

[music in]

Leila Battison: Many insects will also use sound as a defense mechanism.

Nancy Miorelli: A lot of insects will make some sort of sound to try and convince you that you definitely don't want to eat it.

Leila Battison: Unlike mating calls, these sounds are meant to be heard by creatures more like us.

Nancy Miorelli: While their mating sound may be in the ultrasonic range where we can't hear it, an alarm call may cover a broader range of wavelengths. So that way, even big stupid mammals like ourselves can hear it.

Nancy Miorelli: And that's like a kind of angry, like “Ch-ch! Leave me alone. I just made this big scary noise. I'm so scary. Please don't eat me."

Leila Battison: Here's a tiny walnut sphinx caterpillar, doing its best to sound big and tough.

[sfx: walnut sphinx caterpillar]

Leila Battison: And here's what it sounds like when someone irritates a wasp right next to a microphone.

[sfx: squeaking wasp]

Leila Battison: Tiny bullet ants also make a sound to try and scare off predators… although it does sound a bit like someone making kissy noises.

[sfx: Bullet ant squeak]

Leila Battison: Sometimes, the sounds can come from insects you'd least expect.

Nancy Miorelli: There's this weird butterfly here that's called the Cracker Butterfly and it makes a cracking sound with its wings.

[sfx: Single Cracker butterfly]

Nancy Miorelli: The first time I saw one, I was like, "Did that butterfly just crackle?" And when I looked it up later, it was like, "Yeah, it's the Cracker Butterflies and we don't really know how they make their sound, but they do crack.”

[sfx: Cracker butterflies]

Nancy Miorelli: We think it's like a territory thing, but unsure.

[sfx: Cracker butterflies]

[music out]

Leila Battison: There's a lot to learn about why certain bugs make the sounds they do. But the mechanics of how they make those sounds are usually easier to understand.

There are three main ways, and you can think of these almost like the three sections of an insect orchestra.

Nancy Miorelli: The first is called stridulation, and that is just when they rub body parts together. An example would be like a katydid or a cricket that's rubbing its wings together, [sfx: cricket stridulating] or a grasshopper that's rubbing its legs. [sfx: grasshopper stridulating]

Nancy Miorelli: When the body parts are rubbing together, there's some sort of texture, some sort of grooves or some kind of ribbing that makes kind of like a scratchy noise.

Leila Battison: It's similar to a scraper instrument, like the Güiro.

[sfx: Güiro]

The second kind of insect noise-maker is more like a drum.

[sfx: bongos]

Nancy Miorelli: So cicadas make their sound by vibrating a membrane called a timbal.

Leila Battison: The timbal is typically found on the insect's back, just under its wings. It's a thin membrane that can vibrate up to 7,000 times a second.

[sfx: Cicada buzzing]

As it vibrates, the rest of the insect's body acts as an amplifier.

Nancy Miorelli: Basically the inside of a cicada is a boom box, the tracheal system has been modified, and it's just a big hollow drum inside to be able to magnify the sound.

Leila Battison: The last component of this insect orchestra is the most rare. It's a bit like an accordion.

[sfx: accordion chord]

Nancy Miorelli: Insects don't breathe through a nose like we have. Insects breathe through little holes that line the length of the body.

Leila Battison: These breathing holes are called spiracles.

Nancy Miorelli: And some insects, like the hissing cockroaches, can actually push air through those spiracles and hiss very much like we would.

[sfx: hiss sound]

Leila Battison: Here's a Madagascan hissing cockroach doing what it does best.

[sfx: Madagascan hissing cockroach]

So you've got your scraper...

[sfx: scraper + cricket]

Leila Battison: Your drum...

[sfx: drum + cicada]

And your accordion.

[sfx: accordion + hissing cockroach]

Leila Battison: Put them all altogether...

...and you've got the ultimate insect orchestra.

[sfx: insect orchestra]

Leila Battison: These sounds might seem pretty simple. But by tuning their pitch and altering their song patterns, insects can do a lot with what they've got. And that allows each species to make itself heard - even in really loud environments.

[sfx: natural soundscape]

Nancy Miorelli: When you walk outside, you're bombarded with a bazillion different sounds, and those bazillion different sounds are coming from lots of different species from completely different groups.

Nancy Miorelli: You have frog noise and bird noise and toad noise, and just human noise when someone's playing their music too loud, right?

[music in]

Nancy Miorelli: And so that's why it's so important for some insects to call at a different frequency, or to call louder, or to call lower, to call higher to get through all of that gunk.

[sfx: mole cricket]

Nancy Miorelli: These insects need to be able to find each other and hear each other. So it's pretty amazing that they can.

[music in]

Leila Battison: The variety and volume of noises that insects make is truly remarkable. But that’s not all these creatures can do with sound. Some species are capable of mind boggling sonic feats, like crafting tools to make themselves louder, [sfx: tools] and even jamming the sonar of bats. [sfx: radar jam]

That's coming up, after the break.

[music out]

MIDROLL

[music in]

Insects are great at making noise, but the way they do it depends on their bodies. For instance, katydids rub their legs against their wings to create a chirping sound.

[sfx: katydid]

The seventeen year cicada makes its high pitched call by rapidly vibrating a membrane on its abdomen.

[sfx: 17 year cicada]

And some Hawk Moths can push air through holes in their bodies to produce a squeaking sound.

[sfx: death's head hawk moth]

Leila Battison: But all of that bug to bug communication is only possible if they can hear each other. Now when you think of insects, you might not immediately think of ears. But in the insect world, ears are actually extremely common.

Natasha Mhatre: So somebody posed the question, "How do you make a ear?"

Leila Battison: That's researcher Natasha Mhatre. She's the one who mentioned crickets as the source of that Cuban diplomat's recording. Natasha says that from an evolutionary standpoint, making an ear is actually quite simple.

Natasha Mhatre: It turns out what you need to do to make a ear is basically have a cavity inside the body. [sfx: cavity] and then you need to stretch a membrane over that cavity. [sfx: membrane]

Leila Battison: When a soundwave hits that membrane, [sfx: impact] it causes it to vibrate. [sfx: deep vibration] So the last thing you need is a neuron that allows the animal to perceive that vibration. [sfx: neural crackles]

Natasha Mhatre: If you can then hook a neuron somewhere close to that membrane or on the membrane, [sfx: plug in] you're golden. You have a ear.

[music in]

Leila Battison: Insects belong to a larger group of animals called arthropods, which is Greek for jointed legs. And all of those joints means lots of neurons to know what they’re doing, which means…

Natasha Mhatre: They have essentially spread out over all of their body, several opportunities to make a ear. Their anatomy is sort of suited to that.

Leila Battison: As a result...

Nancy Miorelli: We keep finding ears in kind of weird spots on insects.

Natasha Mhatre: Crickets have them sort of below the knee on the fore legs.

Nancy Miorelli: Praying mantises, they have a single ear in the middle of their thorax.

Natasha Mhatre: Locusts have them on the side of their abdomens.

Nancy Miorelli: In lacewings, their ears are on their first wing.

Natasha Mhatre: Butterflies have them at the base of the wing.

Nancy Miorelli: Katydids ears are on their first pair of legs, kind of right next to the elbow joints.

Natasha Mhatre: And perhaps my most favorite is the moth that hears with its mouthpart.

Leila Battison: That's right, its mouthpart. As strange as it might sound, certain species of hawkmoth have bristles right next to their tongues that can detect soundwaves. It'd be like if we could hear with our lips.

Natasha Mhatre: Yeah, it's insane.

[music out]

Leila Battison: Insects may be great listeners, but some still need an extra boost to make themselves heard. Especially if they're naturally high pitched.

Natasha Mhatre: Insects want to sing at low frequencies because low frequencies travel really far. Like a high pitch sound really decays really quickly. But a low pitch sound will go on forever.

This is why things like foghorns are so low in pitch.

[sfx: foghorn]

It’s so that sound can travel as far as possible.

Leila Battison: But if you're a tiny tree cricket, your wings just aren't big enough to produce a low sound that can travel across a big field. So you've got to get creative.

[sfx: cricket chirp]

Leila Battison: When a cricket sings, soundwaves ripple out from its wings in both directions. [sfx: rippling soundwaves] Each soundwave is like a series of peaks and valleys.

But when the peak of one soundwave hits the valley of another, they cancel each other out. This makes the overall sound quieter. It's the same principle behind noise canceling headphones.

Leila Battison: For many species, a bit of noise cancellation isn't a big problem. But others need every decibel they can get.

[music in]

Natasha Mhatre: So some insects have tried to find a way to do better. And one way that they have found to do better is to use a baffle.

A baffle is something that blocks sound from moving in a particular direction.

Natasha Mhatre: So what they do is they basically climb on a leaf [sfx: insect legs climbing], chew a hole in the leaf [sfx: chomping], a hole that's more or less, exactly the same size as their wings. It puts its head through the hole in the leaf [sfx: head squeezing through a hole] and then holds its wings absolutely flush with the hole and then sings. [sfx: tree cricket]

Natasha Mhatre: So when this wing is vibrating back and forth, the leaf makes sure that the sound that's coming out from the front of the wing doesn't interact with the sound that's coming out from the back of the wing.

Leila Battison: The result is that the sound is amplified.

Natasha Mhatre: So these insects are making a tool to make louder sounds.

[music out]

Leila Battison: As well as using tools, insects are capable of other amazing feats: like disrupting the natural sonar of bats.

[sfx: Bat echolocating]

Leila Battison: Bats hunt using echolocation, making ultrasonic clicks that bounce off everything around them.

These recordings have been slowed down to make them low enough for us homosapiens to hear.

Leila Battison: As the bats hear the echoes, they can form a mental picture of their surroundings, including any tasty prey.

[sfx: bat catches a bug]

But some tiger moths can disrupt that system.

Nancy Miorelli: When they hear the ultrasonic pulses, they will make a clicking sound, and that clicking sound jams the bat echolocation.

[sfx: bat echo + moth clicks]

Leila Battison: This messes up the bat's mental picture of where that moth is, making it much harder to catch.

[music in]

Leila Battison: Jamming bat sonar is impressive enough. But what's even more bizarre is how they do it.

Nancy Miorelli: They make a sound with their genitals. And that's what jams that bat sonar.

Uhhh, okay.

Leila Battison: Yep. And moths aren't the only insects that use these organs for sound.

Nancy Miorelli: The loudest animal by body size is actually a water boatman that lives in Europe. And it lives at the bottom of rivers.

Leila Battison: They're called water boatman because when they swim, they kind of look like a boat with oars. These creatures are less than half an inch long, but their mating call is really loud.

Nancy Miorelli: It produces a sound around 99 decibels.

That's about as loud as a blender full of ice cubes.

Nancy Miorelli: And the males make this sound, 99 decibels, by rubbing its genitals against his abdomen.

[sfx: Water Boatman]

Leila Battison: Strangely, their predators don't seem to notice this sound at all.

Nancy Miorelli: For whatever reason, there's not like a predator that is picking up on that particular cue, and so the females are probably picking males that can be the loudest. So we just see those insects get louder [sfx: water boatman] and louder and louder and louder, and they're at the bottom of rivers and you can walk next to the river and still hear them. That's how loud they are.

[music in]

Leila Battison: The fact that water boatmen can make all of that noise without attracting hungry fish is pretty unusual. Typically, adaptations by prey go hand in hand with adaptations by their predators.

Nancy Miorelli: There's this thing called the evolutionary arms race.

Leila Battison: Essentially, predators are always trying to find their prey, and the prey is always trying to avoid being found.

Nancy Miorelli: So whatever starting point you start at, your predator eats all the easy ones to find.

Leila Battison: Over time, the prey has to adapt by getting faster, by being better camouflaged, or by changing the way they sound.

At the same time, the predators might also get faster, or develop a better sense of smell, or get better at hunting in groups.

Nancy Miorelli: And then you get this evolutionary arms race of the predator being better at being able to find the prey item, and the prey item being better at avoiding the predators, whatever that case may be.

[music out]

Leila Battison: One way that prey can avoid detection is by getting quieter. For example, in Hawaii, there's an invasive wasp that preys on crickets.

[music in]

Nancy Miorelli: So this wasp will find crickets, it will lay its eggs on the crickets. The larva will hatch, it will eat the cricket alive, and then emerge from the body cavity.

Leila Battison: Gross. And also…

Nancy Miorelli: Not great for the cricket. But the wasp was using the cricket's sound to locate the crickets.

[sfx: Cricket song]

Nancy Miorelli: So in the past, like 20 years-ish, these crickets have gone silent. They don’t make sound anymore.

Natasha Mhatre: Within a few generations, the whole of the island, that species of cricket was completely silent.

Nancy Miorelli: Because there was so much pressure from those parasitic wasps that quiet crickets lived and loud crickets died.

Leila Battison: The saddest thing is, these crickets are still trying to sing. They still rub their wings together, but they've lost the grooves that make the stridulating sound.

Natasha Mhatre: They evolutionarily became silent. They just lost their singing parts.

Leila Battison: This is actually one of the fastest evolving traits that scientists have ever seen in animals.

[music in]

Leila Battison: Unfortunately, insects around the world are facing more than just invasive predators.

Natasha Mhatre: We’re also really, really changing the world in terms of just the temperatures. So we're having something of an insect apocalypse.

Leila Battison: And bad news for insects is bad news for everyone.

Nancy Miorelli: We tend to notice things are wrong when we're like, "The whale population is declining! The lion population is declining!" when really there were signs that the ecosystem was struggling way before then.

Nancy Miorelli: Insects are the base of the ecosystem, right? That's what like birds and lizards eat. But when you start losing the base of that ecosystem, by the time your lions and your whales are having problems, there's so much damage done to that ecosystem that it's hard to come back from.

In order to protect these ecosystems, we need to understand them. And that's going to require more research, and more scientists like Nancy and Natasha.

Leila Battison: But even if you don't become an entomologist, you can still step outside and enjoy the insect chorus.

[sfx: insect chorus]

Depending on where you are, or when you're listening, you might hear the chirp of a cricket…

[sfx: insect chorus]

Leila Battison: Or the scratch of a katydid...

[sfx: Katydid sound]

The hum of a grasshopper...

[sfx: Grasshopper]

Leila Battison: Or the buzz of a cicada.

[sfx: Cicada]

So the next time you hear a bug, see if you can find it, and take a closer look.

Nancy Miorelli: I hope it makes people curious about what they have in their backyard. I think when people go outside, they're like, "Oh yes, noise."

Leila Battison: But that noise can be really important. It can teach us about the creatures we share the planet with, their evolution over millions of years, and what changes we might expect in the future.

You might even find a new favorite sound, to pick out among the insect chorus.

[sfx: tree crickets]

Natasha Mhatre: I like the tree crickets singing at night. I really like them.

Leila Battison: There's even a quote about them, which Natasha loves.

Natasha Mhatre: "If moon beams could sing, this is what they would sound like."

[music out]

Twenty Thousand Hertz is produced out of the sound design studios of Defacto Sound. Hear more at Defacto Sound dot com.

Leila Battison: This episode was written, produced and reported by Leila Battison.

It was story edited by Andrew Anderson and Casey Emmerling, with help from Grace East. It was sound designed and mixed by Joel Boyter and Justin Hollis.

Thanks to our guests, Nancy Miorelli and Natasha Mhatre. Nancy has a Youtube channel called SciBugs. There, you can learn all kinds of interesting things about insects. Natasha's team does a ton of fascinating research on insect communication. For more, follow the links in the show description.

I'm Dallas Taylor. Thanks for listening.

[music out]