Inside The Race To Save Honeybees From Parasitic Mites

KATHLEEN DAVIS: This is Science Friday. I’m Kathleen Davis. If you’re a beekeeper, you know this time of year can be really stressful as you try to make sure your honeybee colonies are happy and healthy and ready for a busy season of pollination. And there’s one thing you really don’t want to see in your hives, a tiny parasitic mite. SciFri producer, Rasha Aridi, is here with more. Hi, Rasha.

RASHA ARIDI: Hi, Kathleen. Yeah, as you said, there’s a teeny, tiny mite that is absolutely wreaking havoc on honeybee populations, which is really scary because these bees are not doing too well. A few months ago, I went out to Colorado AND I met Dr. Sammy Ramsey, an entomologist at CU Boulder and his team of bee experts. They’re working on studying this mite so they hopefully one day can take it down. I met them in this beautiful field nestled among Boulder’s rolling hills right off the main road. There are around 15 beehives all lined up next to each other and we were going parasite hunting.

SAMMY RAMSEY: The name for this parasite is a very transformative sounding name but it’s actually called Varroa destructor. So these Varroa destructor mites have earned this name. It’s not melodramatic by any means. They are incredibly destructive organisms. We lose between 1/3 and 1/2 of our bee colonies, like, nationally every year.

RASHA ARIDI: Because of these mites?

SAMMY RAMSEY: The primary driving factor is Varroa destructor. There are other things that are going on and I don’t want to make it seem like there is a single problem. It’s multifactorial. But what we do know is that these parasites are at the center of the web of problems. Because pesticides are one issue, but because the parasite literally feeds on the tissue that breaks down pesticides, pesticides are a lot more deadly when they are around. In addition to that, poor nutrition is a big issue for bees, but it becomes a huger issue when they feed on the tissue that stores excess nutrition and allows them to get through these dearths in their nutritional context.

RASHA ARIDI: So the mites eat the bees’ stomach like a smoothie, a bee smoothie?

SAMMY RAMSEY: It is actually a bee smoothie in a lot of ways. So it’s referred to as the fat body. And the fat body does the job of the liver of the bee. It’s a part of their, like, endocrine system. It regulates their hormones. It regulates their immune system and it also stores nutrients and regulates their metabolism. In addition to all of that, you can’t eat normal stuff because if there’s any toxic component to it, you can’t break it down.

RASHA ARIDI: So it wouldn’t kill the bees as much as make their lives miserable.

SAMMY RAMSEY: It makes their lives miserable enough that oftentimes, they die as a result, especially from viruses that they come in contact with. The tough part now is that when colonies start collapsing, the bees that lived inside of those colonies that no longer have a place to live will begin to drift to any nearby colonies that they can go to. And the worst part about that is the mites that you get under those circumstances are likely to be a lot more virulent.

Just like there are different strains of COVID-19 that can cause all kinds of issues, there are more virulent strains of Varroa. The ones that kill a colony and then their bees fly over to yours and then deposit their mites there, those are typically more virulent mites.

RASHA ARIDI: Oh, no.

SAMMY RAMSEY: Yeah.

RASHA ARIDI: These mites are too good.

SAMMY RAMSEY: They are. And I mean, honestly, it’s not just that the mites are too good, it’s that the bees have never dealt with something like this before.

RASHA ARIDI: Our honey bee is not native to the US. It evolved in Europe and colonists brought the species over with them. The Varroa mites, on the other hand, evolved in Southeast Asia. The bees over there can deal with the mites pretty well but the European honeybees can’t. They didn’t evolve to, which makes them very susceptible to infestations.

What about the native bees? They also wouldn’t have encountered these evil little mites, right?

SAMMY RAMSEY: The good thing about these evil little mites, if I can say that there’s a good thing about them, these mites are very species-specific. They have attuned themselves to the life cycle of the bees, to the exact timeline of the bees, to the endocrine system of the bees, the different levels of hormones and things. And so they can’t just offload themselves into a bumblebee colony and expect that they’re going to be successful.

We have never seen them reproducing in bumblebees and wasps, even though sometimes they’ll accidentally end up in one of those colonies. They just can’t seem to make it work.

RASHA ARIDI: Ah, so those other bees just kind of lucked out.

SAMMY RAMSEY: They did luck out. The problem is, there’s another parasite currently spreading around the world that is related to Varroa destructor but its populations grow much more quickly and it is the least species-specific.

RASHA ARIDI: No.

SAMMY RAMSEY: Yes, it’s called the Tropi mite. My research is divided between Varroa mites in the US, and then I go to Asia for about three months every year and study the Tropi mites there, because my goal is to make sure we don’t take our eye off the ball.

RASHA ARIDI: Now that I know exactly what we’re dealing with, we’re ready to open up a hive.

SAMMY RAMSEY: During the height of the summer, there’s thousands upon thousands of these little hexagonal cells in the colony that have a developing baby bee inside. The queen lays an egg. In a matter of days, that egg hatches, turns into a larva. That larva spends a few days developing into a pupa. And it’s at this stage right before it turns into a pupa where the parasite jumps inside.

Now the bees try to put a layer of wax over the cell to stop parasites from getting in there. And the parasites have learned what the larva smells like right before it’s about to get capped. So they have totally outsmarted the bees and learned to jump in. And instead of the cap protecting the larva from the parasite, it protects the parasite from the bees and from our pesticides.

RASHA ARIDI: Inside the hive that Sammy wanted to crack open, there were around 20,000 bees, which is a fairly small colony. And for the bees to let us in, we had to distract them.

SAMMY RAMSEY: All right, ladies. When we pump this smoke at them, they start sticking their heads inside of the cells and consuming honey because it mimics the experience of there being a forest fire in the area. The behavior that they then have under that set of circumstances is, we should probably consume as much of the honey as we can, store it in our honey stomachs because we’re going to have to fly off with it if this fire gets too close to us. And so it gives them something else to worry about as top priority instead of you.

All right, ladies. Let’s see what’s happening with your babies. Let me see if I can get a nice little frame out here for you.

RASHA ARIDI: And then it was time to shake off the bees, shoo them away so that we could take a closer look at the cells and try to find some with baby honeybees that could be carrying the Varroa mites.

SAMMY RAMSEY: So I’ve taken to counting to three in random languages when I do this.

RASHA ARIDI: Nice. What language are we getting today?

SAMMY RAMSEY: Uh, Japanese. Ichi, ni, san.

[BUZZING]

SAMMY RAMSEY: Right? Oh, wow, this frame might be the one.

RASHA ARIDI: By the one, Sammy means a hive full of Varroa mites.

SAMMY RAMSEY: There’s a Varroa mite sitting right on the body of this bee right there, that red bump that’s on the back of the bee.

RASHA ARIDI: It looks like a little bug pimple.

SAMMY RAMSEY: It does look like a little bug pimple. This little bug pimple is unfortunately mobile. And if it were a pimple, proportionally, it’d be the size of your hand.

RASHA ARIDI: What?

SAMMY RAMSEY: Yes.

RASHA ARIDI: [GASPS]

SAMMY RAMSEY: It’s one of the largest external parasite body ratios that we see in the scientific world.

RASHA ARIDI: So at this point, right in front of us is a tray that looks like a giant sheet of honeycomb. There are bees ducking in and out of the tiny, sticky, hexagonal cells.

SAMMY RAMSEY: Some of these cells, like the rim of the cell, is just a little bit higher up than it is on the others. And those are cells where the larva has finally reached the age where they are teenagers, and so they’ve reached a point where they are about to be capped and the parasites know this.

RASHA ARIDI: The cells that are capped or covered with wax kind look like someone shoved a yellow crayon through them. We can’t see inside so we have no idea if there’s any unlucky baby bees with Varroa mites chewing on them.

SAMMY RAMSEY: And so we are going to grab some of them, we’re going to take them to the lab, and we are going to hope that if there are parasites inside this cell, we can transfer them into our imaging system. Normally, what goes on under these cell cappings is not quite a mystery to us, but it’s very hard for us to actually discern because it’s pitch black inside of the colony. So you can’t see anything and it’s too small to get a camera inside.

We’ve created these artificial cells in the lab that are made of beeswax, but two of the walls of the hexagon is replaced with high optical clarity glass. So you can actually position them in an incubator that I’ve designed to have a microscope and a camera over it. And then you can watch what the parasites are doing inside of the cell instead of what we used to do, where we would just open the cell at random intervals and say, OK. That’s what they were doing at two hours in, at five hours in, at three days in, at 10 days in. Now we get to watch the entire process start to finish.

So if you want to see the next part of this process, we’re going to head back to the lab at CU Boulder, the Boulder bee lab.

RASHA ARIDI: Let’s do it.

SAMMY RAMSEY: Let’s do it.

RASHA ARIDI: I’m excited. Sammy and his team packed up a couple frames from the beehives into a carrier. It looked like a briefcase full of honeycomb. We drove over to Sammy’s lab to get a close-up view to see how exactly he can spy on baby bees, and what he can learn from doing so.

SAMMY RAMSEY: So we have just arrived in the Boulder bee lab. And now the hands-on part of actually moving the mites into these cells gets to be conducted.

RASHA ARIDI: Sammy and his team started by taking out one of the frames that we brought with us in the bee briefcase. They propped it up on a stand so that they could see every little cell and they opened up each capped cell very tediously, one by one by one, to see if any of the babies nestled inside of them had mites feeding on their guts.

SAMMY RAMSEY: So we’re going to lift the bee up, look for the mite, and then if that bee has a mite, we’re going to transfer the mite, the brood food, and the bee into one of our artificial cells.

RASHA ARIDI: Dr. Madison Sankovitz, a postdoc in Sammy’s lab, showed me how to do this.

MADISON SANKOVITZ: So I’m going to use these short forceps to open up one of these cells so I can kind of cut around the wax capping.

RASHA ARIDI: It looks like earwax.

MADISON SANKOVITZ: Oh, yeah. It is essentially earwax. So close, so close. There’s this little baby bee I’m pulling out of here.

RASHA ARIDI: It looks like a little grub or, to be frank, like a booger.

MADISON SANKOVITZ: Totally, yes. Grub/booger, both are acceptable. And then, there’s a Varroa mite in the cell. We hit the jackpot.

SAMMY RAMSEY: This particular bee is going to become an experiment. She’s going to survive, but unfortunately, the parasite that was already inside of this cell with her is just going to continue doing what it would have done otherwise under our watchful eyes. So no bees will be murdered in the making of this cell unless the mite murders them, and then that will unfortunately be a data point.

RASHA ARIDI: That boogery bee will get packed into a little glass chamber. It kind of looks like the very top of a mechanical pencil. And inside its little room, it has everything it needs, baby food, a bed of wax, and of course, a Varroa mite.

SAMMY RAMSEY: So, because I want to keep this system as natural as possible, I’m taking the cap off of a cell that was just capped by a bee. And so if there are any potential pheromones or things that these mites need to smell in this process, I’m going to make sure that they do that. So we’re putting the cap on here.

RASHA ARIDI: So the goal is, like, neither the bee or the mite really notice that they are not in the hive anymore.

SAMMY RAMSEY: That is exactly the goal. And it is a hard goal to pull off because honeybees work so hard to make that hive such a distinct home.

RASHA ARIDI: Once the bee is tucked into its little cell, it gets placed into a one-of-a-kind imaging machine. It maintains perfect humidity and heat and has cameras that spy on the bees for about 10 days as they go from a slimy looking larva to a beautiful honeybee. Sammy and his team call it the mite insight system.

What do you learn from spying on them and like, watching them do this and invading all of their privacy?

SAMMY RAMSEY: I am invading their privacy and it’s very important that I do so because before, when people wanted to see what was going on with the mites, they had to open individual cells after a certain amount of time. And the influx of air into the cell lets them might know the jig is up. They know I’m here. And they stop doing all the things they were doing before. They stop reproducing. They will sometimes continue to feed. But most of the time, they’ll just try to get out of the cell. At that point, you’ve created a stop motion system where you can tell what was going on in the moment you opened the cell, but before and after is a mystery.

Well, I’m tired of those mysteries. I want to see everything that happens here and I want to be able to catalog all the different behaviors and how long they’re doing each thing, and discover if there are any potentially weak links in their life cycle. And so what we end up doing here is by filming all 10 days that they’re running around down here inside of the cell, we have the opportunity to really see all the different things that they’re doing and actually catalog all of it, and turn it into a data set.

RASHA ARIDI: For example, Sammy can see if and how a baby honeybee could take down a mite. One way the bees do this is with silk which they use to build their cocoons. If the bee picks up on a mite, it’ll go into a frenzy and bolts that might down to the bottom of the cell using silk fibers. The key is for the bee to do this before the mite latches on.

SAMMY RAMSEY: It only takes like three or four silk fibers and that mite can’t get up anymore. And so I’m wondering, is there a way that we can jumpstart that ability and kind of more strongly encourage them to do this really fast? Because if they can outsmart the mites at this stage of the life cycle, they can stop them from hopping on their face and doing all the nefarious things they do during the rest of the time these bees are in the cell.

RASHA ARIDI: Watching the mites chow down on the bees in the imaging system also gives Sammy and his team insights into how the mite keeps itself alive.

SAMMY RAMSEY: Do you see that Varroa mite running around in there? So both mites survived but did not reproduce. Why? All right, so here’s the thing. There is a infertility rate in colonies that ranges wildly, and we don’t know why. The last paper I read about, it was like between 8% and 62% in the study that they did. Like, the mites will go into the cell, do their fairly normal behaviors of feeding, but then just for whatever reason, choose not to reproduce. We don’t know what’s up.

Sometimes, I will talk about these mites being clever, being fascinating, being interesting, and people bristle at that. But my interest in these mites, my ability to peer into their life cycle and learn about them, it is really, really, really important for us being able to find out the weak links in their life cycle, us being able to find out how to disrupt their capacity to exploit the bees. If we don’t understand them, we can’t accomplish any of that.

RASHA ARIDI: And this imaging system gets really detailed photos and videos of the mites feasting on the baby honeybees’ insides, to the point that we can even see their mouthparts move. Sammy walked us over to a computer to show us very close up what goes on in the little bee chambers.

SAMMY RAMSEY: Ha, ha, check this one out. That is a Varroa mite with its mouthparts embedded in the fat body tissue of the bees. So all this squishy white stuff that you see here, this is the bee’s liver. So you can actually see this mite embedding its mouthparts in this bee. It’s wackadoodle.

RASHA ARIDI: All this brings us to one last question. How do we beat the Varroa destructor mites?

SAMMY RAMSEY: That’s a great question. This parasite is now officially a cosmopolitan parasite. It is present pretty much everywhere bees are kept, so we’re going to do everything we can to understand them. Because in order to beat them, we’ve got to figure them out.

When you’re looking at things and you don’t know what you’re looking for that some of the best science happens. We’re not looking for anything specific. We’re just looking to understand them better than they’ve been understood previously. And then it’s possible that something will present itself. We don’t know if it’ll be a spray. We don’t know if it’ll be gene drive or some sort of double stranded RNA disruption of their genetic code. We don’t know yet, but we are going to figure that out by intensely studying these organisms, learning about their reproduction, their feeding, their digestion, their entire life cycle, and then we’ll know what options are available to us.

RASHA ARIDI: A huge Thanks to Dr. Sammy Ramsey, Dr. Madison Sankovitz, and Christopher Borke for speaking with me. To see photos from our field trip to Sammy’s lab, go to sciencefriday.com/honeybees. I’m Rasha Aridi.

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