[RADIOLAB INTRO]

MOLLY WEBSTER: Hey, I'm Molly Webster. This is Radiolab. So one of my first pieces at the show, like actually, kind of my very first "Molly" piece, was this episode called "Goo and You." It was about what happens inside a chrysalis when a caterpillar crawls in and a butterfly or moth crawls out. Like, what happens in that middle space. And it's one of my favorite pieces because it feels like, I don't know, it's got, like, science and poetry and philosophy. And it's also just this meditation on what it means to change. And though it was my first piece, which—[coughs]—happened over 10 years ago, it is still actually the piece that I get the most feedback about. Like, I still get emails about it, people want me to do workshops on it. It inspired some famous person's, like, wedding. And then a month ago it popped up again when one of my editors was like, "Yo Molly, this fabulous young radio reporter basically made a 'Goo and You' sequel." I listened to it; it's great. It's a story that revisits the scientist, drags her whole family in to this kind of international tale, and then it becomes a meditation not just about change in an individual, but across generations. And so what we want to do for you is play an excerpt of this piece. It's called "Caterpillar Roadshow." It's from this audio magazine called Signal Hill, and the reporter is Annie Rosenthal. So here's Annie.

ANNIE ROSENTHAL: In the spring of 2022, my mom went into the mailroom at the university where she works in DC. In her box, there was a big, flat envelope addressed to her, Martha Weiss. She didn't recognize the sender: Jo Nagai. J-O, no E. Inside, there was a handwritten letter, four pages long.

MARTHA WEISS: So shall I read you part of the letter?

ANNIE ROSENTHAL: Please!

MARTHA WEISS: "To Martha Weiss. Hello. Nice to meet you. My name is Jo Nagai. I'm from Japan. I live in Kobe, Japan. I'm in the second grade at Ibuki Elementary School. When I found your research on the internet, I was so delighted!!"

ANNIE ROSENTHAL: Two exclamation points!

MARTHA WEISS: Two bold exclamation points.

ANNIE ROSENTHAL: My mom is an entomologist—she studies insects. And she gets letters from strangers pretty often. They're mostly about this one study she worked on. She and her student were studying moths, and they figured out that an adult moth could remember something it learned as a caterpillar. Even after metamorphosis, the memory carried through. It made kind of a splash.

[ARCHIVE CLIP, Molly Webster: What's your—what's your feeling, like, coming out of this?]

[ARCHIVE CLIP, Martha Weiss: My feeling is "Wow!"]

ANNIE ROSENTHAL: This is my mom on Radiolab.

[ARCHIVE CLIP, Martha Weiss: I think it's amazing that a caterpillar can have an experience, go into its chrysalis, five weeks pass, emerge as a seemingly different organism, and that it still can recall experiences that happened to it when it was a caterpillar.]

[ARCHIVE CLIP, Jad Abumrad: Freaking cool, I gotta say.]

ANNIE ROSENTHAL: There were a lot of interviews like that. And a lot of emails. But the letter my mom picked up that day at work was different from any of the fan mail she'd gotten before. For starters, the author was a kid in second grade, writing from the other side of the world. But more importantly, he was writing to tell her that he was an insect scientist himself. In the letter, Jo described his discoveries.

MARTHA WEISS: "I've studied swallowtail butterflies for three years."

ANNIE ROSENTHAL: In kindergarten, he'd investigated how long a swallowtail butterfly could stay alive if it got stuck in the chrysalis. In first grade, he'd found caterpillars that molt more often than usual. But now, Jo said, he was hoping to try something a lot more complicated.

MARTHA WEISS: "I've always thought that my butterflies could remember me even after their metamorphosis, because they always flutter around me whenever I try to let them go into nature. But sadly, some say that's impossible and ridiculous. I have some questions to you. Have you ever experimented in swallowtail butterflies? I want to try to find if a swallowtail butterfly could remember what it learned as a caterpillar."

ANNIE ROSENTHAL: Jo, an eight year old, wanted to replicate my mom's groundbreaking experiment because he wanted to know if his butterflies could remember him.

MARTHA WEISS: I came home and said to Dad, "Look what I got in the mail." You know, this is the most fun letter I ever got.

JOSH ROSENTHAL: Yeah, I was there when the package came.

ANNIE ROSENTHAL: That's my dad, Josh.

JOSH ROSENTHAL: Full-size sheets of paper with his handwritten letters, photos of himself.

MARTHA WEISS: A very cute kid with glasses.

JOSH ROSENTHAL: And his butterflies.

MARTHA WEISS: He's looking through a magnifying glass. And then there are two pages of data figures.

JOSH ROSENTHAL: I mean, she was laughing and reading with her mouth wide open. [laughs] I thought it was wonderful.

ANNIE ROSENTHAL: Jo had no idea what a perfect correspondent he'd found, because the only audience my mom respects more than her entomological peers is small children.

MARTHA WEISS: They are curious about stuff, and they haven't figured out that it's boring to look at plants or bugs.

ANNIE ROSENTHAL: She's diagnosed elementary school as the last chance to intervene before the veil of indifference descends.

MARTHA WEISS: Seventh grade, eighth grade, "Is it gonna be on the test? Do we have to know that?" Second grade, third grade? Bingo.

ANNIE ROSENTHAL: And something horrible must happen in fifth and sixth grade.

MARTHA WEISS: Puberty. Everybody becomes more interested in each other than the bugs, which is good because it helps our species persist.

ANNIE ROSENTHAL: Outside her academic work, my mom has spent decades weaseling her way into children's classrooms to make the case for the humble arthropod. She brought poop-shooting caterpillars to my kindergarten. She organized cricket races at my sister's 10th birthday party. Every year, she and her colleagues crawl around the woods collecting caterpillars to show off at schools around the city. They call it the Caterpillar Roadshow. So with Jo Nagai, my mom wasted zero time in writing him back.

MARTHA WEISS: "Dear, Jo Nagai. I was so excited to get your packet in the mail. It was such a fun and interesting letter. I loved reading about your experiments and your discoveries, and I'm so happy to have a new friend in Japan who loves caterpillars and butterflies as much as I do."

ANNIE ROSENTHAL: To be clear, she didn't actually think Jo could recreate her experiment. The way she and her grad student, Doug Blackiston, had done their study, was by training caterpillars to hate a specific smell, and then testing whether, once those caterpillars became moths, they still hated the smell. They did the training with this elaborate lab set-up where they'd release the chemical smell, then give the caterpillar an electric shock, so it would associate the smell with pain. Not totally a kid-level project. So in that first letter, my mom suggested Jo try something simpler like teaching butterflies to learn colors.

MARTHA WEISS: "I could help you test this with your swallowtails, which might be a great research project for third grade."

ANNIE ROSENTHAL: So here you're giving him the old, "Why don't you try colors before memory through metamorphosis?"

MARTHA WEISS: Exactly. "I could write so much more, but want to send this off now so you will know how happy I am to have heard from you. Your friend, Martha Weiss." And then I included some pictures—a zebra swallowtail butterfly and an eastern tiger swallowtail, just to show that we both are swallowtail aficionados.

ANNIE ROSENTHAL: A few weeks later, she got a response.

MARTHA WEISS: "Dear Professor Martha Weiss, thank you very much for your reply. I was so happy and surprised to have a reply from you. I couldn't believe at first. Thank you very much."

ANNIE ROSENTHAL: Jo politely expressed interest in her color-learning experiment and thanked her for the butterfly photos.

MARTHA WEISS: "Their blue is so beautiful and like deep ocean."

ANNIE ROSENTHAL: But he stuck to his guns on the memory stuff.

MARTHA WEISS: "I really want to prove it's possible that my butterflies can remember what they learned as a caterpillar. I don't want to give up now. I really need your help."

ANNIE ROSENTHAL: And Jo wasn't waiting for her approval. He told her he'd already started adapting her protocols for his own at-home lab.

MARTHA WEISS: "But I don't have any devices in my house. I can't make electronic shocks."

ANNIE ROSENTHAL: This wasn't what my mom had expected. The letter was so serious—Jo was so serious. So that summer, they became regular pen pals. In his emails, Jo kept her up to date on his work. And he was confident. Like, he wasn't afraid to question my mom's research methods. Why, for example, she'd chosen the chemical she'd used to train the caterpillars.

MARTHA WEISS: "I have no idea why you picked ethyl acetate for the experiment of Manduca sexta." I felt a little bit defensive about my use of ethyl acetate.

ANNIE ROSENTHAL: Still, in every email, Jo thanked my mom for her time and attention.

MARTHA WEISS: "I know you're so busy, but I'm so happy when you write me back."

ANNIE ROSENTHAL: In the fall, he wrote to say his study was done. It was 33 pages in Japanese, but he'd helpfully translated the basics. He said he'd done essentially the same study as my mom—trained caterpillars to hate a smell, tested whether they'd avoid it as butterflies. He'd used a little muscle therapy device to give the shocks, and lavender oil instead of that toxic chemical for the smell. So the caterpillars learned to hate the lavender. And, according to Jo, when those caterpillars became butterflies, 80 percent of them still avoided the smell. If what Jo said was true, not only had he replicated my mom and Doug's groundbreaking experiment at home over summer vacation, but he'd found their same results in a whole new species. They'd studied moths, but he was the first person in the world to show that memories could persist through metamorphosis in butterflies.

ANNIE ROSENTHAL: And what did you think when you got that email?

MARTHA WEISS: I was flabbergasted and delighted. And in this letter I thought, "Holy cow, he's a real scientist, and he's figuring out new stuff."

ANNIE ROSENTHAL: As the months went on, my whole family became obsessed with Jo. We talked about him all the time.

JOSH ROSENTHAL: You just don't expect to see or hear that level of sophistication out of anybody without a PhD.

ANNIE ROSENTHAL: My dad again.

JOSH ROSENTHAL: Definitely not someone in elementary school. [laughs]

ISABEL ROSENTHAL: We'd go to see friends or family or something and we're like, "You gotta know, here's the latest updates on Jo Nagai."

ANNIE ROSENTHAL: My sister, Isabel.

ISABEL ROSENTHAL: What's the new tea? What's he up to these days? What has he discovered? What kind of, you know, like, advances has he made?

HARRISON SMITH: Every time I talked to your parents, I get the parents' update and I get the Jo Nagai update.

ANNIE ROSENTHAL: My boyfriend, Harrison.

HARRISON SMITH: And there's always something exciting.

ANNIE ROSENTHAL: For example, in September 2022, Jo presented his research to scientists at Shinshu University, then at Tsukuba University and Saga University. He also graduated from second grade. And then in the spring of 2023, Jo wrote to my mom rather casually that he had a whole new research question. He wrote, "By the way, I'd like to study if memories can be inherited to the next generation this summer." Jo wanted to study if caterpillar children could remember things that had happened to their parents. "I know that most people generally think memories can't be inherited from ancestors," Jo wrote. But he'd found a recent study that suggested it might be possible in nematodes, these tiny, freaky worms. If they could do it, he thought, why not swallowtails?

MARTHA WEISS: It had never occurred to me to even ask that question.

ANNIE ROSENTHAL: Jo's first study was advanced, but this was a whole other realm—epigenetics—the ways environment and experience can change how our genes are expressed, even across generations. It's a field of biology my mom calls "the new frontier." And it's not exactly her area of expertise.

MARTHA WEISS: I don't live on the frontier. I live in the heartland. And so when he said, "I read the nematode paper," I had to go scramble and find the nematode paper. I was too embarrassed to ask Jo which nematode paper, because I didn't want him to be too much ahead of me on the up-to-the-minute research.

ANNIE ROSENTHAL: The inheritance of memory has only been studied in a few species: those worms, some mice. My mom wrote back to Jo, "This is a controversial topic, but that doesn't mean that it doesn't happen. We can learn more by doing more studies." Jo forged ahead. He did his experiment again, but tested a second generation too, to see if they avoided the same smell he'd trained their parents to hate. And a few months later, he wrote to my mom that the results were clear. His butterflies had passed their memories on to their children.

ANNIE ROSENTHAL: When I was growing up, bugs were a central feature of our household. They were just always around. My mom raised silkworms in a box in the dining room, and she kept cicada exoskeletons in a jar in the kitchen, which my teenage friends found horrifying. She was waging the pro-bug campaign on the home front. And for a while, it worked.

MARTHA WEISS: You don't squish bugs, and you don't scream when you find a spider in the bathtub. I consider that a victory.

ANNIE ROSENTHAL: But I guess at some point, that dreaded veil of indifference fell over me, too—or maybe it was just puberty. By the time I was in high school, I was less interested in bugs and more interested in people. These days, my extracurricular reading is about stuff like historical memory, how experience moves down through time. That's what I'm always trying to report on, although my editors tend to steer me towards the news. But now, my mom's tiny genius pen pal was saying he had proof that in this one species, what happens in a parent's early life can show up in their kid: the inheritance of traumatic memory. The caterpillar body keeps the score. My mom is always warning me against anthropomorphism, but in a way, it seemed like Jo was asking the same question I often am: how we get to be who we are.

MARTHA WEISS: "How to say butterfly in Japanese." Cho! Oh, I know that. I knew that because Madame Butterfly.

ANNIE ROSENTHAL: A while back, my mom got this note from Jo.

MARTHA WEISS: He said, "Dear Professor Martha Weiss, hello, how are you? Blah, blah, blah. Is it getting colder in your town, too? How do your caterpillars and butterflies spend during cold winter? Well, do you know the International Congress of Entomology—ICE 2024? The website is as follows," with the URL. "It will be held in Kyoto, Japan in 2024. Are you going to come and attend it? If you come there, I'd like to see you and can show you around Kyoto, Osaka, and Kobe, my town."

ANNIE ROSENTHAL: My mom did, in fact, know the International Congress of Entomology. It's one of the biggest conferences in the field. It was happening in August. She hadn't been planning on going this year, but a personal invite from Jo changed the equation. And once she'd decided to go, there was no question. Actually, all of us would come to Japan. My entire family plus my boyfriend bought plane tickets. In the months leading up to the trip, my mom helped Jo with his application to present a poster at the conference. She thought he had basically a dissertation's worth of research. She, on the other hand, was bringing a plan for an experiment she hadn't actually started yet.

ANNIE ROSENTHAL: Maybe he can lend you one paper.

MARTHA WEISS: Yeah. Just—just come on.

ANNIE ROSENTHAL: [laughs]

ANNIE ROSENTHAL: I loved the story of Jo, this child prodigy, showing up my mom, esteemed entomologist. And I was telling everyone I knew about his big finding. But now we were about to actually meet him, and part of me had started to worry. Over two full years of correspondence, my mom and Jo had never actually spoken. In fact, she wasn't even writing him directly.

ANNIE ROSENTHAL: You're emailing his mom's email.

MARTHA WEISS: Because he doesn't have his own email. So his mother is the invisible portal through whom we communicate. So his mother is named Sarry. And so I get an email from Sarry, and it says, "Hi, this is Jo." And then I write to Sarry and say, "Hi, Jo." Although two times ago I wrote and said, "Hi, Sarry, this is Martha Weiss. Jo invited us to come visit him in Kobe, and so I just wanted to check in with you." And have I heard from Sarry? No. But I did hear from Jo what hotel he and his mother, Sarry, will be staying in in Kyoto, so I made reservations at that hotel too.

ANNIE ROSENTHAL: Which I'm interested in this dynamic. Like, do you feel like you need to talk to his mom?

MARTHA WEISS: I kind of do.

ANNIE ROSENTHAL: Because you're sort of emailing a child all the time?

MARTHA WEISS: Well, I feel the science is between me and Jo. But when he says, "Come visit me at my home in Kobe," that then I need to check with his mom.

ANNIE ROSENTHAL: Have you ever thought about, like, Zooming him?

MARTHA WEISS: I guess I did initially, but I don't know, there's something sort of nice about writing.

ANNIE ROSENTHAL: It's sort of Jane Austen of you guys.

MARTHA WEISS: Yeah, it's a little more Jane Austen, exactly. I think he feels that way too.

ANNIE ROSENTHAL: I mean, do you like the mystery? Like, do you like that we just, like—I mean, Jo Nagai is like a national hero in our house.

MARTHA WEISS: [laughs] Yes, I do like the mystery. I think that's part of it. And to be honest, I'm a tiny bit nervous about meeting him in person.

ANNIE ROSENTHAL: What are you nervous about?

MARTHA WEISS: I don't know. I mean, I guess our correspondence is—it's all about science and butterflies, and there's nothing else in it. Like, what if he's, like, a mean kid who has temper tantrums and, you know, kicks and screams and bites his baby sister, or—you know?

ANNIE ROSENTHAL: I can't imagine that Jo is a biter. [laughs] But are you at all worried that he's a catfish?

MARTHA WEISS: Well, let me just say that I only recently learned the term "catfish." And some people have said to me, "Is this kid for real? Do you think that this is an elaborate ploy?"

ANNIE ROSENTHAL: You're sort of a trusting correspondent.

MARTHA WEISS: I'm a trusting correspondent.

MOLLY: Hey, this is Molly again. We are gonna take a quick break. But when we get back, we will find out: kid or catfish, when Martha and her entire family go to Japan. That's coming up after break.

MOLLY: Hey, this is Radiolab. I'm Molly Webster. And today we are playing a super special story for you called "Caterpillar Roadshow." It is about a bug scientist and a young boy in Japan who strike up a long distance email correspondence because they're both really excited about the scientific work of caterpillars, butterflies, moths. Up until this point, though, they have never met in person, but that is about to change. Let's listen in.

FLIGHT ATTENDANT: Welcome to Tokyo. The local time is 2:55 in the afternoon on August 15. Please stay comfortably seated until the seatbelt sign has been turned off.

ANNIE ROSENTHAL: When we got to Japan, Jo still had a few days of school before the conference, so we had to find ways to distract ourselves. Which wasn't hard—we were surrounded by amazing and surprising things, like the public toilets that automatically make the sound of a waterfall and birds chirping to cover up any embarrassing pee noise. And the beautiful glowing vending machines on every other block. At any time of day or night, you can pop in a couple hundred yen and get a whiskey highball, or a sippy cup of apple juice, or a perfect sports drink called Pocari Sweat. But the most amazing and surprising thing? Bugs were everywhere. In the trees outside temples, restaurants, but also, on t-shirts, book covers, street signs. On the subway, we saw a poster for an insect show at the Tokyo Museum of Nature and Science. Inside, the hall was packed with hundreds of people—more excited than I've ever seen anybody in a museum, honestly. And they weren't just stopping at the iridescent butterfly wings, they were reading about the way a spider disguises itself to mimic an ant, structural color, parasitic wasps.

AKIKO KAWAHARA: Yeah, you see that a lot in Japan. You know, you go to just a public park in the center of Tokyo, and you'll see a parent with a butterfly net with their child carrying a little insect cage.

ANNIE ROSENTHAL: This is Akito Kawahara. He's a big deal in bug science, the director of a center for butterfly and moth biodiversity in Florida. And he grew up in Tokyo. I called him to ask, basically, is this a thing? Or was I just on high alert for bug stuff, like the bug-shaped toys we saw all over the city?

AKIKO KAWAHARA: So, gacha gachas, so what it is, is essentially it's a gumball machine where you put some money, a dollar or two, into a machine ...

MARTHA WEISS: One. Two. Three.

AKIKO KAWAHARA: And a ball comes out.

MARTHA WEISS: Ready?

ANNIE ROSENTHAL: Yep.

AKIKO KAWAHARA: And inside the ball there's a toy.

ANNIE ROSENTHAL: It's a big boy!

AKIKO KAWAHARA: And there's a whole bunch of insect ones. And some of these insect ones are extremely realistic.

ANNIE ROSENTHAL: Yeah, look how much you can make it move around.

MARTHA WEISS: That's a deal for an articulating beetle.

ANNIE ROSENTHAL: A steal. And then, look, we should get another one, so they can fight!

ANNIE ROSENTHAL: Japanese pop culture isn't just full of bugs, it's full of youth insect enthusiasts. Akito told me about a popular video game where you play a kid helping a scientist collect and identify escaped bugs. And the guy who created Pokémon? He started out wanting to be an entomologist. The game came straight out of the years he spent scouring the wilderness for bugs. People here have been insect fans for a long time. More than a thousand years ago, Japanese nobles kept crickets in cages to listen to their chirps. In the late 1800s, kids' magazines aggressively advertised bug collecting to patriotic and masculine boys. By the 1930s, insect hobbyist societies had hundreds of members who'd go on collecting trips, tromping around the forest and posing with their butterfly nets like big game hunters. Beetles in particular became kind of a status symbol. An exotic pet.

AKIKO KAWAHARA: It got to the point where, you know, people were trying to grow the biggest beetles, and then they would sell them. And in one case, one of the beetles sold for an incredible $90,000.

ANNIE ROSENTHAL: One of Akito's closest friends actually raises beetles.

AKIKO KAWAHARA: Every time I go back to Japan, he's driving a different colored Ferrari. And oftentimes I joke that I might've made the wrong decision in my career to become a scientist, and maybe I should have just reared beetles and had a life that was different from what I'm doing now.

ANNIE ROSENTHAL: Papilio xuthus, is that right?

MARTHA WEISS: That's his butterfly.

ANNIE ROSENTHAL: At the museum, I thought about Jo. From the distance of my mom's kitchen in DC, his passion had seemed totally unique and mysterious. Here, it suddenly seemed a lot less random. We found an exhibit about swallowtails, and my mom texted Sarry, Jo's mom, a picture. Sarry sent back an emoji of a rabbit with exploding heart eyes. They'd finally made direct adult-to-adult contact. She and Jo and his brother were coming to meet us in two days. We're on the train, finally on our way to meet Jo.

MARTHA WEISS: I can't go through with it. I'm getting off at the next station and going back in the other direction.

ANNIE ROSENTHAL: Too late.

ANNOUNCER: Next station, Himeji.

ANNIE ROSENTHAL: We pull into the station, get off the train, and there they are, just on the other side of the turnstile.

SARRY NAGAI: Hi, hello!

MARTHA WEISS: Nice to meet you.

ANNIE ROSENTHAL: I'm trying to be present for the meeting, and also fumbling to get my recorder rolling.

SARRY NAGAI: Hello, how are you?

MARTHA WEISS: This is my daughter, Annie.

ANNIE ROSENTHAL: Sarry, in her late 30s, has a ponytail, a white blouse, a parasol for the sun. And then there are the two boys.

JOSH ROSENTHAL: You must be Harry?

ANNIE ROSENTHAL: Hayato—or Harry—age 13. Mid-eighth grade growth spurt, in a huge t-shirt and baseball cap. And next to him, the man himself.

JOSH ROSENTHAL: Jo?

JO NAGAI: Yeah, I'm Jo.

JOSH ROSENTHAL: A real pleasure. I'm Josh.

ANNIE ROSENTHAL: He's a pretty small guy, with very discrete bangs, like the tines of a feathery fork. Big Harry Potter glasses and a round little face that makes him look younger than 10. He's wearing a traditional jinbei—a matching wrap-around shirt and shorts—and carrying a backpack about half his height.

MARTHA WEISS: And you have your butterfly net!

JO NAGAI: Yes. I have it.

ANNIE ROSENTHAL: He and my mom are both smiling big, but a little awkward with each other, like meeting somebody for a first date after you've bared your soul to them over a text. For the next few hours, Jo takes the reins. As we walk around the city, he makes the most of opportunities for viewing wildlife. For example, a pigeon we pass.

JO NAGAI: We can't touch it. But it is very cute.

ANNIE ROSENTHAL: We visit Himeji Castle, Jo's favorite castle, and he points out big, gulping fish swimming in the moat.

JO NAGAI: Oh! It is beautiful.

MARTHA WEISS: Oh yeah, they're blue! Flashing blue.

JO NAGAI: Yeah. Beautiful. Wonderful.

ANNIE ROSENTHAL: And he helps us work on our manners.

JO NAGAI: If you eat food, first you say "Itadakimasu."

ANNIE ROSENTHAL: Itadakimasu?

MARTHA WEISS: Itadakimasu. What does that mean?

JO NAGAI: We eat the birds and fish and a lot of creatures.

MARTHA WEISS: Mm-hmm?

JO NAGAI: So we have to thank ...

MARTHA WEISS: To say thank you.

JO NAGAI: Thank you.

ANNIE ROSENTHAL: To say thank you to the creatures?

JO NAGAI: Creatures, yes.

ANNIE ROSENTHAL: And can you say it again?

ANNIE ROSENTHAL: Jo seems to be amazed by basically every living thing we see around us. He's sweet and solicitous, and also, a totally normal kid. Impatient in the heat, hungry for junk food, constantly proposing a game.

MARTHA WEISS: What do you do?

JO NAGAI: Pull.

ANNIE ROSENTHAL: Like, who has the stronger pine needle.

MARTHA WEISS: Okay.

ANNIE ROSENTHAL: So Jo's is stronger?

JOSH ROSENTHAL: Jo's is stronger.

MARTHA WEISS: Are you stronger than me?

JO NAGAI: Yeah.

ANNIE ROSENTHAL: At lunch, Sarry tells us that Jo has been invited to present his research to the crown prince of Japan in a private meeting at the beginning of the conference. He seems unfazed—he says he's just a little nervous. But he's star-struck by my mom. When we finish eating, she presents Jo with a hand lens, a little magnifying glass attached to a ribbon, just like the one she wears around her neck. He makes very direct eye contact and says, "I love this so much. I want it."

[singing]

ANNIE ROSENTHAL: Outside the restaurant, a woman is performing a Japanese version of "Part of Your World," from The Little Mermaid. And somehow it feels exactly right. It's a million degrees out and we're soaked in sweat. All awkwardness gone, everyone is giddy. It feels like a fairy tale—castles and princes, a sage advisor, a young apprentice. We take a bus to the edge of the city and ride a glass gondola high up into the mountains. At the top, we climb out into a cool, sweet-smelling forest. And a symphony of bugs.

ANNIE ROSENTHAL: Ooh, what's that?

JO NAGAI: It is a beetle. Martha, it is a beetle!

MARTHA WEISS: You found a beetle?

JO NAGAI: Beetle. Yeah. Do you need a case? I have a case.

MARTHA WEISS: Yes, please. Yes, please. I made a mistake to not bring my cases with me.

ANNIE ROSENTHAL: Yeah, Jo came prepared.

JO NAGAI: I will give you.

MARTHA WEISS: Thank you very much.

ANNIE ROSENTHAL: At the top of the mountain, Jo sees something. He leaps forward, his net zigzagging back and forth like a banner. And then ...

JO NAGAI: Martha, I did it!

MARTHA WEISS: You got it?

JO NAGAI: Whoa! I take it.

JOSH ROSENTHAL: Wow.

MARTHA WEISS: Oh, that's the one you showed me!

JO NAGAI: Yeah.

MARTHA WEISS: Oh, that is beautiful! Jo showed me a picture of this and said that we might find these.

ANNIE ROSENTHAL: It's an East Asian tiger beetle. Maybe the most flamboyant bug I've ever seen, with a bright green head, long antennae, blue and rust-colored splotches all over its back.

MARTHA WEISS: Oh my goodness. Look at that—look at that color!

SARRY NAGAI: Yes. So shiny, and metal color.

ANNIE ROSENTHAL: Sarry convinces Jo to let it go.

JO NAGAI: I will release it.

MARTHA WEISS: Can I hold it for one second? The wings are—whoop! Goodbye! Good luck!

JO NAGAI: He's very powerful.

MARTHA WEISS: Yeah, he's a strong flyer.

ANNIE ROSENTHAL: The moon is rising over the city. We catch the last gondola down in the pink light. After dinner, my family boards the train back to our hotel. Hayato and Jo wave from the platform for a full minute, and once our train starts moving, Jo runs after it.

MARTHA WEISS: Outside the window of the train, we just saw him speeding along and keeping up with us until our bullet train pulled away and we left him behind. And I just felt like it was the best day ever.

ANNIE ROSENTHAL: When I was six, a brood of periodical cicadas emerged in DC—billions of bugs that spend their whole lives underground and tunnel up to the surface just once, after seventeen years. For a few chaotic weeks, the city is completely overtaken by their whine. As you might imagine, while most people saw the cicadas as a menace, my mom was basically hysterical with excitement. Late at night, the bugs would climb up trees around the neighborhood to molt. And one night, she let me and Isabel stay up until midnight to watch. We walked down the block with flashlights, stopping at a tree. Just above my head, these bright white cicadas with ruby-red eyes were stretching backwards out of their old shells, so new to the world they were still damp. It felt like I'd been let in on a huge secret, catching them in this private moment in the dark.

ANNIE ROSENTHAL: I was reminded of that night walking into the conference center. Here, I was an interloper again, surrounded by thousands of entomologists, the international denizens of my mom's world. They weren't the most visually intimidating group—lots of cargo shorts and T-shirts with bug puns on them. But this was their turf. They were keepers of bug knowledge not yet released to the larger world. I was unprepared for the scene in the poster hall. Alongside the adults, there was an army of young scientists.

GIRL: Hello, we are from Takatsuki Senior High School. And today we would like to talk about turn alternation of pill bugs.

ANNIE ROSENTHAL: These were Jo's peers. At 10 years old, he wasn't even the youngest presenter.

TAKERU INAGAKI: I'm Takeru Inagaki. I'm in the fourth grade of elementary school. I've been collecting butterflies since I was six years old.

ANNIE ROSENTHAL: Takeru was approximately three feet tall.

TAKERU INAGAKI: Thank you for listening to my presentation.

ANNIE ROSENTHAL: Arigato gozaimasu!

SHUSEI: My research is about leaf-rolling weevils. So do you know leaf-rolling weevils?

ANNIE ROSENTHAL: Um, no, I don't know them.

SHUSEI: Okay, so let me explain.

ANNIE ROSENTHAL: Thank you.

ANNIE ROSENTHAL: Shusei is 14.

ANNIE ROSENTHAL: It's a very impressive presentation.

SHUSEI: Yes, thank you very much.

ANNIE ROSENTHAL: Are there many students your age who are doing entomological research?

SHUSEI: Yes. Many kids, students, are doing some kind of research about the insects. But this one is really amazing.

ANNIE ROSENTHAL: Yeah. [laughs]

ANNIE ROSENTHAL: He was looking over at Jo, whose poster was right next door.

ANNIE ROSENTHAL: Has he—did he explain it to you already?

SHUSEI: Actually, he's my friend. Our house is really close that we can meet each other often.

ANNIE ROSENTHAL: And do you guys discuss your research together?

SHUSEI: Yes, yes. He is four years younger than I. But the things that he is doing is more level high.

ANNIE ROSENTHAL: Jo was in full networking mode, suit and tie, handing out his business card.

JO NAGAI: I'm Jo Nagai. Nice to meet you.

ENTOMOLOGIST: It's so nice to meet you. So can we take a picture with you and the poster?

JO NAGAI: Oh, yes.

ENTOMOLOGIST: You have a bright future in front of you. No doubt about that.

ANNIE ROSENTHAL: Hanging around Jo's poster, I met Masato Ono, the conference chair.

MASATO ONO: President of organizing committee.

ANNIE ROSENTHAL: Oh, okay. Wow, okay. Very nice to meet you.

ANNIE ROSENTHAL: And Akito Kawahara, the big-name butterfly expert from earlier.

AKIKO KAWAHARA: He's just incredible. Like, you know, everything that he's done is just, like, incredible. Like, I want him in my lab. I'm secretly like, maybe, like, he wants to do some research in America.

ANNIE ROSENTHAL: We stood there watching Jo together.

JO NAGAI: In the parent's generation, I give the electric shock and the lavender odor. I waited until they became butterflies. And they avoided the lavender odor, so I know they can remember what they learned as caterpillars. In the child's generation, they also avoided lavender odor, so the memories can persist to the next generation.

ANNIE ROSENTHAL: All day, Jo and his poster were swamped. I could barely see him behind his crowd of admirers.

JO NAGAI: [Speaking in Japanese.]

ANNIE ROSENTHAL: That night, back at the Comfort Inn Kyoto, Jo went straight to the hot tub for a triumphant soak. Conventional scientific wisdom says it's easier to remember a painful experience than a positive one, that's why, in their original experiment, my mom and Doug decided to teach their caterpillars to hate a smell—shocking them every time they smelled it.

MARTHA WEISS: And it was clear from the caterpillar's behavior that they were receiving the shock. And I'll just leave it at that.

ANNIE ROSENTHAL: Can you just say what that means?

MARTHA WEISS: [laughs] No.

ANNIE ROSENTHAL: When my mom or her student pushed the button, the caterpillar would start to convulse, and sometimes vomit. When Jo replicated the experiment, he'd taken a different approach. Instead of high-voltage lab equipment, he'd used that little physical therapy device—a pad that emits small amounts of electricity to treat muscle pain. Jo already had one at home to help with pain in his own shoulders.

JO NAGAI: I put the pad on my arms. And inside of the pad there is a caterpillar.

ANNIE ROSENTHAL: So the caterpillar would be sitting literally on Jo's arm, right between the pad and the softest part of his wrist.

ANNIE ROSENTHAL: And so—so did you also feel the shock when they felt it?

JO NAGAI: Yes. Yes.

ANNIE ROSENTHAL: And was it painful to you? Or what did it feel like to you?

JO NAGAI: The first was very good for me, but if I did it every day my arm will be red, pink or red. So I was very—I have pain.

ANNIE ROSENTHAL: The machine has a bunch of different power levels, from one to fifteen. Jo had stopped at level four.

ANNIE ROSENTHAL: And what was your thinking about why—why to use that level of shock and not more shock?

JO NAGAI: Because they—in the level four, they pop out their osmeterium.

ANNIE ROSENTHAL: Osmeteria. Little orange horns that pop out of the caterpillar's head when it gets scared.

JO NAGAI: So I think it was enough for the caterpillar.

ANNIE ROSENTHAL: And so you didn't want to hurt them more than you needed to?

JO NAGAI: Yes.

ANNIE ROSENTHAL: Yes, okay.

ANNIE ROSENTHAL: In the breakfast room at the hotel, Jo got the machine out of his backpack for a demonstration, sans caterpillar.

ANNIE ROSENTHAL: Okay, where do you put it? On my ...

JO NAGAI: Here.

ANNIE ROSENTHAL: He strapped the little pad onto my forearm and pressed the button.

JO NAGAI: Is it coming?

ANNIE ROSENTHAL: I don't—I don't feel it yet. Is it—oh, now I feel it a little bit. Number two. Okay, another one. Three. Oh! I feel it! Oh!

ANNIE ROSENTHAL: It was a crazy feeling, a huge shudder that made my hand jump.

MARTHA WEISS: Did you see Annie's osmeteria come out? [laughs]

ANNIE ROSENTHAL: The science isn't clear on whether bugs feel pain. And as my mom has explained to me, there aren't a lot of rules around how you should treat them as a researcher.

MARTHA WEISS: So, if you're gonna do something with a vertebrate, you have to put in a whole animal protocol. It has to be taken care of in an approved animal care and use facility. There's committees that monitor everything. Invertebrates, nobody cares one iota about.

ANNIE ROSENTHAL: That means it's up to each individual scientist to set their own standards.

ANNIE ROSENTHAL: Well, so what's your personal standard for your approach?

MARTHA WEISS: Compassionate, and treat them as if they feel pain. And try to minimize any pain or suffering while getting our science done.

ANNIE ROSENTHAL: Jo seemed to have different priorities.

MARTHA WEISS: He could have said, "Boy, I really want to make sure that they get it," and crank it up to nine. But he didn't do that.

ANNIE ROSENTHAL: You're thinking of the caterpillars almost as friends, maybe?

JO NAGAI: I think it's a friend.

ANNIE ROSENTHAL: You think it's a friend?

JO NAGAI: But I give the electric shock, so from the caterpillar, I am a bad friend.

ANNIE ROSENTHAL: I talked to Jo for a long time about this. He told me he doesn't actually want to be an entomologist when he grows up. He wants to be a veterinarian.

ANNIE ROSENTHAL: What kind of vet do you wanna be?

JO NAGAI: I can fix caterpillars and insects both.

ANNIE ROSENTHAL: Do you know of—are there other insect veterinarians now?

JO NAGAI: There are no insect vets now.

ANNIE ROSENTHAL: So you might be the first insect vet.

JO NAGAI: Yes!

ANNIE ROSENTHAL: Way back in that first letter to my mom, Jo had told her he wanted to study insect memory because he thought his butterflies remembered him. Jo had a relationship with the bugs he worked with, and that relationship had shaped his questions, his methodology. So many scientists see anthropomorphizing as a cardinal sin, but for Jo, I realized, interspecies empathy was kind of a sleeper strength. All this work had come out of his willingness to wonder what a bug might know or feel. On the last morning of the conference, my mom said there was something we needed to do. All this time, she'd been an advisor to Jo. She'd checked his methods, helped him write his abstract, but she still hadn't seen his actual data—the raw numbers themselves. She didn't know for sure if we could conclude with statistical certainty that his findings were true. When I stopped to think about it, it seemed crazy that we'd made it through the whole trip without looking at this. But when I said that to my mom, she surprised me.

MARTHA WEISS: Is it gonna hold up if we do a statistical test? Are we going to see a significant result? In some ways, it doesn't really matter because a ton of other stuff has happened.

ANNIE ROSENTHAL: And then I surprised myself, because I sort of disagreed. I was still thinking about the science. This thing about memory and generations, I wanted it to be true.

ANNIE ROSENTHAL: This is kinda what I'm trying to understand, like, does this finding matter?

MARTHA WEISS: Does this finding matter? I mean, does—does what I do matter? You know, at some level, yes. At some level, no. Am I curing cancer? No. Am I stopping climate change? No. Am I helping myself and other people understand how organisms work and how they interact with their environment? Yes. And will that help us maybe understand our environments and our planets better, and maybe help us have a little bit more empathy for some of the organisms that we live with? I hope so. But the other reason that it matters is because I care about Jo.

ANNIE ROSENTHAL: Jo. Who'd spent five of his ten years of life on these studies, and reached out to a scientist across the world to help him find answers. This was important to him, and he was important to us. And so we needed to know.

MARTHA WEISS: Three, four, five, six, seven, eight, nine, ten, eleven, twelve, thirteen, fourteen, fifteen, sixteen, seventeen, eighteen.

ANNIE ROSENTHAL: Jo and Sarry brought his research binder to my mom's hotel room.

MARTHA WEISS: ... lavender. How many butterflies?

ANNIE ROSENTHAL: Together, we went through it, page by page.

JO NAGAI: Nine of them went to the sugar water.

ANNIE ROSENTHAL: My mom asked about his controls, and they double checked his counts.

MARTHA WEISS: Three, four, five, six, seven.

ANNIE ROSENTHAL: And then she said they needed to do a test.

MARTHA WEISS: It's a test of probability. And it's how likely something is to happen by chance. If we take our 10-yen coin and we flip it in the air, how many times are we going to get the castle, and how many times are we gonna get the 10?

ANNIE ROSENTHAL: Jo looked at her for a second, a little confused.

MARTHA WEISS: Why don't you do it for me 10 times and tell me each time what you get? Just quickly. Okay, so you've got a 10.

ANNIE ROSENTHAL: Jo and my mom sat at the table.

JO NAGAI: Ten.

ANNIE ROSENTHAL: Sarry and I on twin beds, watching them flip the coin.

JO NAGAI: Palace.

ANNIE ROSENTHAL: In my head, I was cataloguing all the little happenings that got us here.

JO NAGAI: Ten.

MARTHA WEISS: Okay.

ANNIE ROSENTHAL: That Jo found my mom's research, and could understand it. That he had a mom who could and would help him do his own research.

JO NAGAI: Ten.

ANNIE ROSENTHAL: That my mom would be so willing to get on board.

JO NAGAI: Palace.

ANNIE ROSENTHAL: And to rope the rest of us in, too.

JO NAGAI: Ten. Palace.

MARTHA WEISS: Stop.

ANNIE ROSENTHAL: Five tens, five palaces.

MARTHA WEISS: And that is pretty much what you would expect, because they're the same. And half the time it's gonna be one, and half the time it's gonna be the other, right? What if you did that and you got a 10, 10 times in a row? What would you think?

JO NAGAI: The 10 is very heavy.

MARTHA WEISS: That there's something a little weird going on with that coin, right? What we do first when we're doing this test is we figure out what our expectation is, okay? And so for our first generation, we had 44 caterpillars made choices, right?

JO NAGAI: Yes.

MARTHA WEISS: We would expect—if they hadn't learned anything, we would expect that 22 of them, half of them, would go to sugar, Pocari Sweat, and that 22 of them would go to lavender, right?

ANNIE ROSENTHAL: And having just said how valuable the details of the science turn out to be, you don't really need to know how to do statistical analysis to understand what comes next.

MARTHA WEISS: So we're just going to go times two equals 6.07. Okay? Is 6.07 smaller or larger than 3.841?

JO NAGAI: Larger.

MARTHA WEISS: Larger. So that means that this result is very unlikely to happen just by chance. This means that something happened to those butterflies to make them make that choice. So that is what we call a statistically significant result.

ANNIE ROSENTHAL: In the months since we got back from Japan, my mom and Jo have been drafting a paper on his findings together. They're gonna send it to the Journal of the Lepidopterists' Society to tell them, "We think this is really true. Butterflies can remember something they learned as caterpillars—and their kids can inherit that memory, too." In DC, my mom's been reading up on epigenetics. She told me she's been thinking about our conversations, remembering things from her own childhood, and from when she was pregnant with me. She spent a long time in the hospital in the months before I was born, and a student had brought her a bunch of caterpillars to keep her company, next to her bed in a little plastic shoebox. And as her stomach ballooned, with fetus me inside, the caterpillars crawled out of their box and into different corners of the room to pupate.

MARTHA WEISS: As we know, lots of things are going on inside that chrysalis. So they were changing in the same way that you were changing. And then they emerged as butterflies, and you emerged as a little red frog with a weak chin.

ANNIE ROSENTHAL: Oh my God! [laughs]

ANNIE ROSENTHAL: Jo, meanwhile, is finessing his study on butterfly grandchild memory. He's about to finish fifth grade. A Japanese TV station recently aired an episode about him. When he opens the door to the camera crew, MTV Cribs-style, he's wearing the hand lens my mom gave him on a ribbon around his neck.

MOLLY: That was an excerpt of "Caterpillar Roadshow," produced and reported by Annie Rosenthal. That story first premiered on the audio magazine Signal Hill. You can listen to the entire piece, along with a bunch of other great stories from Signal Hill, and you can get that wherever you get podcasts. That's Signal Hill. So this story had sound design and editing by Liza Yeager and Jackson Roach, who I'm proud to say are former Radiolab interns—we miss you guys. They had help on the piece from Leo Wong and Omar Etman. It was fact-checked by Alan Dean. Special thanks to Carlos Morales, John Lill, Marfa Public Radio, the Nagai family, the Rosenthal family and Emma Garschagen for tipping us off to the story in the first place. And that's it. We will be back soon with a brand new full episode of Radiolab. I am Molly Webster. I got to listen this time! [laughs] It was so fun listening with you.

[LISTENER: Hi, I'm Dylan. I'm calling from the St. Lawrence River in upstate New York. And here are the staff credits. Radiolab was created by Jad Abumrad and is edited by Soren Wheeler. Lulu Miller and Latif Nasser are our co-hosts. Dylan Keefe is our director of sound design. Our staff includes: Simon Adler, Jeremy Bloom, Becca Bressler, W. Harry Fortuna, David Gebel, Maria Paz Gutiérrez, Sindhu Gnanasambandan, Matt Kielty, Annie McEwen, Alex Neason, Sarah Qari, Sarah Sandbach, Anisa Vietze, Arianne Wack, Pat Walters and Molly Webster. Our fact-checkers are Diane Kelly, Emily Krieger and Natalie Middleton.]

[LISTENER: Hi, I'm Rafael, calling from Brazil. Leadership support for Radiolab's science programming is provided by the Gordon and Betty Moore Foundation, Science Sandbox, a Simons Foundation initiative, and the John Templeton Foundation. Foundational support for Radiolab was provided by the Alfred P. Sloan Foundation.]

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