
Zombies might seem like the stuff of horror movies, but there are lots of examples of parasites taking over bugs’ bodies and bending them to their will.
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Host/Announcer
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Bert Pinkerton
Thanks. All right, so we're going to fade up on a moonlit field. You can see tall grasses moving in the breeze, little bit of moonlight, and you can see on one of the blades of grass there's an insect with its wings spread wide.
Mindy Weisberger
This is Mindy Weisberger, a science writer.
Bert Pinkerton
It looks like it might be a bee because it seems to be striped with bands of yellow and black. But you get a little closer and you see that it is not a bee. It is in fact a fly. It is a dead fly. And the yellow bands that are striping its body are actually a fungus that has grown inside it and then burst through the seams in its exoskeleton.
Mindy Weisberger
How did this fly become the star of our real life horror movie? Well, several days ago, a spore from a fungus landed on it and the spore buried inside of the fly and then started extending little filaments throughout its body. These fungal tendrils essentially that started digesting the fly from the inside out, consuming its fat cells. Now, the fly, as this was happening, behaved pretty normally, at least at first.
Bert Pinkerton
But over the next few days, the fungus continued to grow, and it started congregating its cells, first around the fly's heart and then around what is the spinal cord in insects, and then around its brain. And then after it had pretty much consumed most of the fat reserves in this fly, it was ready for the next stage, reproduction. So this is where the fly stops behaving like a fly and starts behaving like a fungus in a fly suit. It finds a place where it can climb, and it's thought that getting to a higher position is better for the fungus because it produces these spores that are released in kind of an explosive poof. And the higher they are, the more widely they are likely to disperse. So the infected fly climbs up a blade of grass until it is literally no longer able to walk anymore. Again, stuffed with fungus. So at a certain point, it stops walking.
Mindy Weisberger
It extends its proboscis, which is a little trunk like mouthpart, and oozes out a sticky substance to basically glue it into place. And then the fly dies. Its abdomen cracks open, and the spores come spilling out, ready to land on new flies and infect them. And to increase the odds that a fly will get spored, the fungus turns into a kind of horrible fly fatale.
Bert Pinkerton
These dead fungus striped flies with their big bloated abdomens are very attractive to male flies who are looking to mate.
Mindy Weisberger
Apparently, male flies of this species find big swollen abdomens very alluring. And they also find this scent that the fungus starts to pump out, this chemical signal called uring, too, like a sexy fungal love perfume.
Bert Pinkerton
That also sends a signal to more male flies, like, hey, you know, maybe here's something that you want to, you know, you want to hit that. I'm sorry. That's.
Mindy Weisberger
All of this draws in new victims who, if everything works out, will soon be turned into their own fungal fly puppets. Now, Mindy is a word for this kind of horror story. Zombification. She calls these flies real life zombies. And the fungus that takes them over is a real life zombifier. And it turns out there are a lot of examples of zombies and zombifiers out in nature. There are so many, in fact, that Mindy wound up writing a whole book about them called Rise of the Zombie Bugs. So this is unexplainable. I'm Bert Pinkerton, and today on the show, Mindy will tell us what we know and what we don't know about zombie bugs. Okay, let's start by just defining some terms. What do we mean when we Say like zombifier or zombie. Sure.
Bert Pinkerton
So a zombifier is an organism that manipulates the behavior of its host, and a zombie is an organism that is being manipulated to behave in a way that it normally would not, and which only benefits the parasite that's manipulating it. So to a certain extent, like let's say you catch a cold, you're going to change your behavior because you're feeling sick, you feel like you need to rest more, you need to drink more water. These are all things that help you fight off the infection. So in a certain sense, that's the cold virus generating a change in behavior. But if it's a behavioral change that actually benefits you, for a zombie, the changes to its behavior are not something that benefit the host. They only benefit the parasite. That's what makes it a zombie.
Mindy Weisberger
So it'd be like if I got sick and instead of going into my room and trying to sleep it off, I went and I licked everybody that I could lick in order to spread the cold.
Bert Pinkerton
Exactly. And so there are zombifying viruses, there are zombifying fungi, there are insects that, that are able to zombify their hosts. There are worms that can zombify their hosts. So most of the organisms that they infect are arthropods.
Mindy Weisberger
So bugs, but the colloquial version of bugs.
Bert Pinkerton
Bugs, exactly. I do have to apologize to entomologists because as far as entomologists are concerned, bugs are only insects with sucking mouthparts. However, as we all know colloquially, bugs covers a much broader range. Poor entomologists.
Mindy Weisberger
Do you have personal favorite zombifiers or ones that make you squirm?
Bert Pinkerton
Let's see. So hairworms infect terrestrial insects, but hairworms reproduce in water. And let's say a cricket is infected by a hair worm. Now, the worm grows inside this cricket. It grows to the point where it is many times the length of the cricket itself. Like, to the point where if you look at a cricket that is infected, you might be able to see it moving around in the abdomen. This actually spoke to me because when I was pregnant, during the last month of my pregnancy, the fetus is getting really big at this point. So, you know, it's kind of like the movie Alien, right? Like, you can see a foot, you can see an elbow. You could. It's like, you know, there's something. There's. There's a. Something alive moving around inside your body that is actually kind of what these, these infected crickets look like. But the worm has to get out eventually. So what it does is it manipulates the cricket's behavior to get it to find water and then jump in. And once it's in the water, the worm starts to emerge. So watching a cricket trying to swim in a pool of water while this long thread like worm is slow, slowly over minutes, spooling out from its backside is something I highly recommend watching if, you know, you really want to squeak yourself out.
Mindy Weisberger
Oh, my God.
Bert Pinkerton
It's like, oh, sick. There. There are many, many videos of this on YouTube. That is so freaking nasty.
Mindy Weisberger
This is so gross.
Bert Pinkerton
Tyler's getting exchanged.
Mindy Weisberger
This is so gross. Oh, okay.
Bert Pinkerton
But.
Mindy Weisberger
So there are all these different approaches, you're telling me, that fungi and viruses and insects use to do this. Zombifying. What are the sort of biggest categories of mysteries, I guess, about how they do this?
Bert Pinkerton
Okay. Some of the biggest mysteries start with the moment that the host is infected, because obviously, a body's first response to any kind of infection is going to be an immune response. So the first thing that a zombifier needs to do is to somehow get past that. And so that's a big question is for zombifiers from viruses to wasps to. To fungi to worms, when they get inside an organism where they're not supposed to be, how exactly are they telling their host immune system, no, there's nothing to see here. You can just go. Go about your business. You don't need to. You don't need to worry about me. So that's mystery number one. Yeah, that's a big one. Then, of course, another one is once it gets to the point of manipulation, first of all, what are. What are the cues? How does it decide, okay, now is the right time to, you know, to get this house moving to a place that. Where I need to be. So the description that I gave you earlier of the fly in a moonlit field, there seems to be a circadian rhythm element to the fungus that infects flies, specifically because they start their climbing at night. Got it.
Mindy Weisberger
So mystery number two would basically be, are there things out in the environment that. That trigger a fungal takeover? And how does the zombifier kind of recognize those cues? I guess it sounds like, yeah.
Bert Pinkerton
And the third big question is obviously the nuts and bolts of how is it manipulating behavior?
Mindy Weisberger
Right.
Bert Pinkerton
The thing about this field is that there is still so much that scientists are piecing together about the precise mechanisms of how this works. Behavior is something that is just super complicated, even in insects. So when we look at, for Example, the wasp that parasitizes orb weaving spiders. Scientists have found that in the spiders that are zombified, what the wasp does, it lays an egg on the spider. The egg hatches and the wasp larva essentially piggybacks on the spider and drinks from it like it's a living juice box. And the spider just goes about its business until the larva is ready to reproduce. And then somehow the wasp larvae is manipulating the spider to think that it's time to molt so that the spider makes a different type of web than it normally does, something called a resting web. It's reinforced and it's meant to support the spider and protect the spider while it's molting. And then once that web is done, the wasp larvae drains the spider tri and the spider's empty husk of a corpse drops to the ground. And the wasp larva builds its cocoon and sets itself up in the spider's final web to hang out until it becomes an adult wasp.
Mindy Weisberger
So basically the spider is convinced by this wasp larvae in some way to build a cocoon for uses all of its final webery to like build a really nice little house for the wasp to grow up in.
Bert Pinkerton
I like final webbery. Yeah. So what scientists found is that when spiders start making that final web, their little spider brains are being flooded with ectosteroids, which is the hormone that the spider naturally releases when it's ready to build a molting web. So it's actually, it's almost like it's taking a page out of the spider's existing biochemistry. And scientists aren't sure yet if what wasp larva is doing. Is the larvae actually producing the ectosteroid. Is it somehow triggering its production in the spider through another compound? That's something that they're still figuring out, but clearly it's something that is already sort of baked into the spider's biology that this is a chemical trigger that lets it know now it's time to build this kind of web, except this time it's not going to survive the process.
Mindy Weisberger
So it is sort of a like you couldn't necessarily get the spider to do something that it wouldn't be able to do under any other circumstances, but you can like puppet it to do things that it might do otherwise.
Bert Pinkerton
That seems to be the much more common strategy among zombifiers. But exactly how they're being activated is still, is still a question.
Mindy Weisberger
Why is it important to understand sort of more about how this behavior manipulation works?
Bert Pinkerton
Yeah, that's a really good question, and.
Mindy Weisberger
It is one that we will answer after the break.
Host/Announcer
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Mindy Weisberger
Scientists still have a lot of questions about the precise mechanics of zombification. But if they could learn more about how zombifiers take over their victims, it turns out they could learn a lot that might benefit all of us.
Bert Pinkerton
This, in a lot of ways, is looking at really big questions about how behavior works, which is something that is. Scientists are still piecing this together on so many levels for all different types of organisms because there are so many factors that shape behavior. Some of them are genetics, some of them are biochemical, Some of them have to do with environment, some of them have to do with social relationships. So this is one way of trying to understand behavior writ large.
Mindy Weisberger
You mentioned that these insects suppress the immune systems of their hosts. Is there stuff that we could learn from. From that about, like, how immune systems work in general?
Bert Pinkerton
Oh, yeah. Looking at the immunosuppressive aspect of zombifiers is definitely something that is a huge area of interest because that could inform the development of immunosuppressive drugs, which is just something that would be hugely beneficial to people.
Mindy Weisberger
Right.
Bert Pinkerton
Not that this should be all about what's in it for me, but that is usually a consideration for scientific research. Could there potentially be applications for this that have medical applications? And so there is not yet a direct line between any research into how zombifiers evade their host's immune system and the development of some kind of pharmaceutical immunosuppressive. But that's definitely something that is part of the mix when scientists are following that line of investigation.
Mindy Weisberger
I think about all the insects that invade homes, some of which are beneficial, some of which are less so. Could we potentially borrow from this to, like, fight off pests?
Bert Pinkerton
Pest control is definitely one avenue that scientists have explored as a way of, okay, well, is there some way that we can take what we're seeing these zombifiers do to insects and apply it to insects that we don't like? So baculoviruses, which are these viruses that infect caterpillars and make them climb and then dissolve their bodies into goo. This is something that has been deployed as a strategy for for pest control in China and in Europe, in the US in Brazil. So these types of viruses, they're an interesting alternative to traditional insecticides because they are very targeted, they're less toxic to the environment, they're not harmful to insects that are not their host species and they're not toxic to people. But they're not as quick as I think the insecticides that people have gotten used to. And people like things to be quick and they like them to be. Absolutely. So what seems like is the best way is perhaps to incorporate this alongside insecticides and use this along with other approaches. Because there are a lot of benefits to just, you know, going, going full on zombie warfare to get rid of our agricultural pests.
Mindy Weisberger
Is there any attempt to like design our own, to be like, all right, we really want to get rid of American cockroaches.
Bert Pinkerton
Like you are describing the plot of a zombie movie right now where a team of scientists are working with their, studying zombie bugs and they're like, oh, hey, wouldn't it be great if we could manufacture an artificial version of this zombie virus and release it into the wild? What could possibly go wrong?
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Mindy Weisberger
Well, this does kind of get to a question that I have around all of this, which is maybe a silly question, but, like, could humans be zombified this way? Are we also susceptible to this?
Bert Pinkerton
Well, there are some types of pathogens that are known to manipulate behavior in mammals and indeed in humans too. So rabies, of course, has been around and has been. There have been medical cases of rabies infected humans that are thousands of years old with documentation of the heightened aggression. So there is already a virus among us that can manipulate human behavior. And recently there have been studies into Toxoplasma gondii, which is the pathogen that causes toxoplasmosis. So this is an organism that, its definitive host is cats. So it's, it's very entrenched amongst human populations and in fact many, many people, millions of people carrying Toxoplasma gondii. But it doesn't cause any symptoms. It tends to be dangerous in people that are pregnant or in immunocompromised people. Most of the people who are carrying Taxoplasma gondii have no symptoms. However, there have been studies recently in the last 10, 15 years or so that have looked at people who are carrying the parasite and have found that there does seem to be evidence of certain types of behavior, of being more risk taking, of being bolder in some groups, women being more nurturing and what's interesting about it is that, is that Toxoplasma gondii is known for manipulating behavior in rodents. And what it does is it makes them bolder and less afraid of cats because Toxoplasma gondii needs to reproduce inside cats, so it infects rodents. And then to get back into a cat, it makes the rodent less afraid of and attracted to the smell of cat pee. And that brings the rodent closer to a cat than it would normally go. And then once it's eaten, then the parasite is back inside the cat. And scientists have found that this is true for other animals, too. So hyena cubs that are infected with Toxoplasma gondii are bolder around lions and are more likely to be eaten by lions. Chimpanzees that are infected with Toxoplasma gondi lose their fear of jaguars. And some studies found that people who are infected with Toxoplasma gondii are more likely to make risky business decisions or be bolder in traffic. So there's still a lot of work to be done because obviously human behavior is its own form of complicated. But there is some evidence that seems to suggest that Toxoplasma gondi can shape human behavior, too. What? Did I just blow your mind?
Mindy Weisberger
Yes, that's. So.
Bert Pinkerton
I can send you links to the studies.
Mindy Weisberger
I think I was expecting you to be like, no. Unless you have rabies, you're definitely not.
Bert Pinkerton
Well, do you have a cat?
Mindy Weisberger
No, I don't.
Bert Pinkerton
I have two.
Mindy Weisberger
So there could literally, at this moment, be zombifiers within us, shaping us in some way.
Bert Pinkerton
It's entirely possible. But there are so many things that make us who we are that shape how we behave. There are environmental factors, there are social factors.
Mindy Weisberger
The responsible answer, sure.
Bert Pinkerton
But there might also be zombifiers in.
Host/Announcer
A world where a team of scientists they're working with, they're studying zombie bugs.
Bert Pinkerton
And they're like, oh, hey, wouldn't it be great if we could manufacture an artificial version of this zombie virus and release it into the wild? What could possibly go wrong?
Host/Announcer
Everything goes wrong.
Bert Pinkerton
Kill them. Kill the cockroaches.
Host/Announcer
You can't kill a cockroach if it's already undead. Guys, I think Gregor might have just turned into a cockroach. Coming soon, under the kitchen sink near you.
Mindy Weisberger
There are so many more weird, wonderful zombie stories in Mindy Weisberger's book, that is Rise of the Zombie Bugs. So if you want to read about zombified cicadas or fungi that will remind you of the show, the Last of Us or any number of other skin crawling mildly horrifying things. Please check it out. This episode was produced by Me, Bird Pinkerton. It was edited by Sarah K. Kramer. Meredith Hodnot runs our show. Noam Hassenfeld makes the music. Christian Ayala did the spooky sound design and the mixing on this episode. Melissa Hirsch did not enjoy all the gross bug stuff but she powered through and checked the facts anyway. Thanks Melissa. And the fact is that Julia Longoria and Jorge just are just lovely human beings. Thanks to Brian Resnick Always for co creating the show. Thanks to Jonah for helping, thanks to Charlie Harding, Claire White, Sergio Scardino and Angela Chen for their voice work. And thanks to you for listening. If you have thoughts about this episode, we are@ unexplainableox.com I love hearing from you all, so please email us if you want to support the show and help us keep making it. Please join our membership program. It is@vox.com members and you'll get ad free podcasts, unlimited access to Vox Journalism and if you tell our bosses that you signed up because you loved Unexplainable, it goes a long way. So that is@vox.com members. You can also support us by leaving a nice rating perhaps, or a review, or just by telling people in your life to listen. But Unexplainable is part of the Vox Media Podcast network and we will be back in your feed next week.
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Bert Pinkerton
Excludes Massachusetts.
Host: Bert Pinkerton (Vox)
Guest: Mindy Weisberger, science writer
Date: October 1, 2025
Theme: Exploring the extraordinary natural phenomena of zombification in insects (“zombie bugs”), how these real-life zombifiers manipulate their hosts, and what science is uncovering about these strange relationships and their broader implications.
The Unexplainable team dives into the gruesome, fascinating world of "zombie" bugs—living organisms whose behaviors are hijacked by other forms of life (such as fungi, viruses, and worms). Science writer Mindy Weisberger joins host Bert Pinkerton to discuss her book, Rise of the Zombie Bugs, and to share both the astonishing real-life horror stories and the open scientific mysteries behind them. The discussion ranges from hairworm-infested crickets to fungi that lure new victims through chemical perfumes and even touches on whether humans could ever face a similar fate.
[06:25]
[01:25 – 05:00]
A spore lands on a fly, the fungus digests the fly from the inside, then manipulates it to climb high on a blade of grass to maximize spore dispersal.
The fungus bursts through the fly’s body, releasing more spores and luring in new victims using chemical cues.
Male flies are attracted to these fungus-bloated dead females due to their appearance and a "sexy fungal love perfume."
Memorable Moment:
[08:12 – 13:17]
Hairworms in Crickets: Hairworms grow inside terrestrial insects but have to reproduce in water. They make insects find and leap into water so the worm can emerge, often grotesquely.
Parasitic Wasps and Spiders: Certain wasps manipulate spiders to spin special "resting webs" as a cocoon for the wasp larva, which eventually kills the spider.
[10:12 – 14:50]
Three key questions:
[14:50 – 21:44]
Immunosuppression Insights: Could inspire medical research into immunosuppressive drugs.
Pest Control: Using viruses or fungi that zombify agricultural pests (e.g. caterpillars) as a targeted, less-toxic alternative to pesticides.
[22:13 – 26:10]
Bert Pinkerton: "So hyena cubs that are infected with Toxoplasma gondii are bolder around lions and are more likely to be eaten by lions. Chimpanzees... lose their fear of jaguars. Some studies found that people who are infected with Toxoplasma gondii are more likely to make risky business decisions or be bolder in traffic…” ([24:00])
Mindy Weisberger: "So there could literally, at this moment, be zombifiers within us, shaping us in some way." ([25:41])
Bert Pinkerton: "It's entirely possible. But there are so many things that make us who we are that shape how we behave." ([25:49])
[21:44, 26:10]
On fungal manipulation:
"It starts behaving like a fungus in a fly suit."
— Bert Pinkerton ([02:45])
On the grossness factor:
"So watching a cricket trying to swim in a pool of water while this long thread like worm is slowly over minutes, spooling out from its backside is something I highly recommend watching if, you know, you really want to squeak yourself out."
— Mindy Weisberger ([09:19])
On what zombification teaches us:
"This, in a lot of ways, is looking at really big questions about how behavior works."
— Bert Pinkerton ([18:38])
On the dangers—and humor—of human-engineered zombifiers:
"Like you are describing the plot of a zombie movie right now... What could possibly go wrong?"
— Bert Pinkerton ([21:52])
Rise of the Zombie Bugs by Mindy Weisberger (for in-depth stories and science)
Summary prepared for listeners seeking a rich, structured understanding of cutting-edge science at the spooky intersection of entomology, behavior, and infectious disease—without any ad breaks or fluff.