Short Wave - This common garden plant summons wasps as bodyguards

Episode Date: June 3, 2026

In our latest science news roundup: how nature adapts, for better or worse. When faced with pests, plants may not be able to run away – but that doesn’t mean they’re defenseless. Some have thorns or spines, others have poisonous leaves or berries, and still others have…elaborate chemical defense alarm systems? In a recent study, researchers discovered that the common bean plant, P. vulgaris, has a particularly innovative response to hungry caterpillars: a compound in the caterpillar's spit causes the plants to release a chemical signal that attracts wasps. Those wasps then eat the caterpillars or lay eggs in their bodies, effectively removing the threat. Today on the show, we’re diving into plant science and a round of other new scientific studies with All Things Considered host Sacha Pfeiffer.If you're interested in the fibermaxxing episode Han mentioned, check it out here.Listen to every episode of Short Wave sponsor-free and support our work at NPR by signing up for Short Wave+ at plus.npr.org/shortwave.See pcm.adswizz.com for information about our collection and use of personal data for sponsorship and to manage your podcast sponsorship preferences.NPR Privacy Policy

You're listening to Shortwave from NPR. Hey, shortwavers, Regina Barbara here. And Hannah Chin with our bi-weekly science news roundup. And we're lucky enough to have Sasha Pfeiffer back on the show third time in a row. Hi, Regina. Hi, Hannah. Fun to be back with you. All right, Sasha, our first topic is about beans and bean plants, surprising chemical counterattack against caterpillars, which are a common garden pest. Ah, you know, given that fiber has become such a wellness trend with everybody fiber maxing,

I'll be very interested to hear about this one. I mean, we also have an episode about fiber maxing. It just came out. Yeah. Great. Then we're going to talk about another pest. We're going to be talking about how best to teach mice. And lastly, we've got one more story about pests.

This time it's how the bug repellent deed could have a major Achilles heel. You know, Han, I think today's episode is actually about nature adapting. It's true. Today on the show, adaptation for better and for worse. You're listening to Shortwave, the science podcast from NPR. Okay, Sasha, we have so much to get through, but you talked about fiber maxing, so let's start with beans. Let's do that. The more fiber for the world, the better. Yeah, so this story is an amazing example of plant versus animal warfare.

And it might make you think a little differently about how crafty plants can be in defending themselves. And it all centers around the common bean plant. So this is the one I feel like a lot of grade schoolers grow in classrooms. It's a garden staple, the bush bean or pole bean. and it turns out it has an elaborate chemical defense mechanism. Ah, and what's it defending itself against? I assume some pest or some blight or something? In this case, it's caterpillars.

So, Sasha, in a study out this week in the journal Science advances, researchers described how when caterpillars munch on bean plants, a compound in the caterpillar spit causes the bean plants to release a chemical signal into the air. Think about it as a kind of distress flare that calls in a fleet of wasp, bodyguards. The types of chemicals we were able to measure were known to be attractants to predatory wasps, parasitoid wasps that lay eggs in caterpillars. So this is Adam Steinbrenner. He's a plant biologist at the University of Washington, and he's one of the authors on the study. He says some of the wasps eat the caterpillars. Others lay eggs inside the caterpillars' bodies so their babies

can eat them, really effectively removing the threat to the bean plants. And Sasha, this kind of chemical signal isn't rare. Plants release them all the time. Like, cut grass smells a specific way. That's the plant's chemical response to being wounded. Oh, interesting. The cut grass smelling a specific way reminds me of flowers smelling sweet because they're trying to attract bees. Yeah. Yeah. And these are both chemical responses, right? But the specific compound that attracts wasps is really only triggered via caterpillar spit. So the bean plant doesn't call wasps in if, say, you cut a leaf or if you damage the plant in a different way. And Sasha, this is just one of multiple ways that plants have really

evolved to defend themselves. If you think about the thorns of a rose or the spines of a cactus or bitter, poisonous leaves, or I guess in this case, this strategy, right? Calling in some aerial reinforcements from the insect world. It's like calling in the drones. Yes, exactly. All right, you also mentioned for your second topic, new ways to speed up learning in mice. Tell us about that one. Yeah, so I brought you a study just published in the journal Science. In lab experiments, researchers typically give mice little rewards to help them learn tasks. But, in this study, they found that giving them bigger rewards less frequently actually helped the mice learn a lot faster. Here's Josh Dudman, one of the authors of the study.

We discovered that we had been substantially underestimating how efficiently animals can learn. We could essentially take some of the slowest learners and move them all the way up to the fastest learners. I really want to know what the rewards were. I'm thinking about cheese or peanut butter we put in a mousetrap. What did they use as rewards for these mice? So in this case, the reward was artificially sweetened water, which for what it's worth is also something that humans appreciate. And what sort of things were the mice trying to learn? Well, one was the classic Pavlovian cue.

They were learning that certain sounds meant a reward was coming. And they also had to learn harder things like pulling a joystick or turning a tiny steering wheel right or left to get a reward. So I'm interested in this idea that a bigger amount of reward given less frequently resulted in faster, learning rather than smaller, more frequent rewards. Tell us more about why that worked better. Yeah. Well, we don't know the whole picture, but Josh and his colleagues think it has something to do with dopamine and engagement, right? Dopamine is a chemical that makes you feel good, and then your brain is like, oh, I want to do that again. And when the mice got these big rewards, they got a bigger burst of dopamine. And the scientists say that lasted longer and kept them more

engaged than these little rewards. They also pointed out there might be other factors at play, not just dopamine. Since this is just a mouse study, what does it tell us potentially about human learning? Yeah, so these experiments give insight into what keeps the brain engaged, which might be helpful for future animal experiments. We aren't quite at the point of comparing these experiments to human learning, but it's a step in the right direction. All right. So topic three, we move on to another type of pest in some people's eyes, and that is how our strongest mosquito repellent may have a weakness we didn't know about before? What repellent and what weakness? Yeah, so many people know Diet is an important chemical in many mosquito repellents, but it may have an Achilles heel. Mosquitoes can learn to associate its

smell with dinner. Which is a pretty big deal, right? Because having an effective mosquito repellent isn't just good for avoiding a cheap bite. It also save lives. Mosquitoes can spread really deadly diseases like malaria. Yeah, so tell us more about this, because of course, the reason we wear Diet is to keep mosquitoes away. Yep. So remind us, what is it that Diet does that repels mosquitoes? Yeah, so that's the part that's wild to me. We still don't fully know how exactly Diet works because... It is not as easy as one might think to ask mosquitoes, you know, how does it feel?

How do you smell or taste that? So this is Clement Vidongier. He's a neuroethologist at Virginia Tech who worked on the study, which was published recently in the Journal of Experimental Biology. He says the reason Diet generally works is because it repels mosquitoes. We just know they don't like it for some reason or another. Here's the thing. Previous research shows that repeatedly exposing mosquitoes to D.T.

Made them less repelled by it. And Clement and his colleagues wanted to take it a step further and find out if mosquitoes could learn to actually be attracted to D. This all seems so counterintuitive. So how do you teach a mosquito? Like one of the experiments in my study about rewards, these researchers went back to Pavlov. You know, that study where you ring a bell, you make the dead.

dogs salivate because they think they're going to get fed. And the researchers use the same concept, but instead of a bell, they use the smell of Diet and as a reward, they used a bag of blood or sugar that the mosquitoes could bite and feed on. And the training worked. They found that in a little over half of the trials, mosquitoes actually began to associate Diet with feeding time. And they would actively approach it, even if the reward wasn't there. And when they tested with actual humans, they found that trained mosquitoes would also gravitate

towards a person's hand sprayed with deed, more than their other hand without the repellent. All right, so I feel like I'm confused by this. You put deed on and it's going to attract a mosquito, even though we want Diet to repel mosquitoes. So what does this tell us about Diet's use and effectiveness in the real world? This study shows it's possible for mosquitoes to learn to be attracted to Deat. And that surprised Aliafifi. He's an entomologist and a neuroscientist at Drexel University. He wasn't involved in this study.

But he pointed out that it's unclear whether this sort of thing could happen in the wild. because remember, this required a lot of training mosquitoes. And usually wild, untrained mosquitoes will fly away from deed. Because mosquitoes are not attracted to Diet in real life, so it's very difficult for mosquitoes to experience Diet while blood feeding. So for now, the researchers say, please don't stop using Diet. They emphasize that it's still a very effective repellent in real world situations.

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So, Sasha, did you enjoy our pest control adaptation episode? I did. Makes you think differently about beans, I think. Everybody needs more fiber, right? Does anybody get enough? Not in America. Yeah, over 90% of us are not getting enough. Not good.

Well, come back anytime, Sasha. Thank you so much. Thank you. This episode was produced by Mallory U and Aruneyer. It was edited by Christopher and Taliatta. Tyler Jones checked the facts. David Greenberg and Tiffany Veracastro were the audio engineers. I'm Regina Barber.

And I'm Hannah Shin. Thanks for listening to Shortwave, the science podcast from NPR.