Not So Fast, Murder Hornets

16:51 minutes

a group of people in futuristic protective gear in a forest surrounding a tree with equipment
A team of scientists remove a section of a tree that contained an Asian Giant Hornet nest in Blaine, WA on October 24, 2020. Credit: Washington State Department of Agriculture

This past spring, you might have seen many headlines about murder hornets making it to the U.S. This is the sensationalist nickname for the Asian Giant Hornet, a large insect native to East and South Asia that preys on honey bee colonies. 

Since late 2019, there have been several sightings of these hornets in Washington state. Just last month, the first Asian Giant Hornet nest was discovered in the U.S., in Blaine, Washington, which is on the U.S. and Canada border. On October 24th, that nest was successfully eliminated by a group of scientists from the Washington State Department of Agriculture (WSDA) and the U.S. Department of Agriculture (USDA). 

Joining Ira to talk about why it was so important to destroy this nest are two entomologists who worked closely on this effort: Chris Looney, with the WSDA in Olympia, and Jackie Serrano with the USDA in Wapato, Washington.

hands holding two very large hornets
The Asian Giant Hornet is quite large. Credit: Washington State Department of Agriculture
a tree split open, revealing a large hornet nest in its core
A tree trunk split apart reveals the large Asian Giant Hornet nest. Credit: Washington State Department of Agriculture

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Segment Guests

Chris Looney

Chris Looney is an entomologist with the Washington State Department of Agriculture in Olympia, Washington.

Jacqueline Serrano

Jacqueline Serrano is a research entomologist with the United States Department of Agriculture in Wapato, Washington.

Segment Transcript

IRA FLATOW: This is Science Friday. I’m Ira Flatow.


Back in the spring, the headlines started to come in. Murder hornets have made it to the US. This prompted a lot of us to say, um, what the heck is a murder hornet? And is murder really their MO?

The proper name for these insects is Asian giant hornet, and they’re native to East and South Asia. Since late 2019, sightings of these hornets have been reported every once in a while in Washington state. All right, let’s cut the music. We’re talking about the flight of the murder hornets here, not the bumblebees. Thank you.

Last month, the first nest of these invasive hornets were discovered in the United States in Blaine, Washington, which is on the US-Canada border. The good news? That nest was taken out successfully. Why is this a good thing? Well, joining me are two guests who were instrumental in this effort, Dr. Chris Looney, entomologist for the Washington State Department of Agriculture in Olympia, Washington. Welcome to Science Friday.

CHRIS LOONEY: Hey. Hi. Thanks.

IRA FLATOW: You’re welcome. Dr. Jacqueline Serrano, research etymologist for the US Department of Agriculture in Wapato, Washington, welcome also to Science Friday.

JACQUELINE SERRANO: Thank you for having me on.

IRA FLATOW: Let’s talk about this. Chris, where do you think the name murder hornet come from, to begin with?

CHRIS LOONEY: It seems to have been related to a New York Times reporter by a Japanese entomologist. He was talking to him about the impacts they might have on human health. And it seemed like almost as an aside. He said, oh, yeah, we kind of call them murder hornets here as a nickname. That doesn’t seem to actually be in common use, to my knowledge. Most of the Japanese-speaking people I’ve spoken with refer to them as osuzumebachi, these giant sparrow bees.

IRA FLATOW: But is it an accurate description? Can they kill people?

CHRIS LOONEY: They can kill people, sure, primarily through anaphylactic shock, just like any other kind of stinging hymenoptera. Rarely through mass stinging events, and that is just because they are so big and can administer so much venom that if you get too many stings, your body can’t cope with it. But they definitely don’t murder people. So that’s a real misnomer in the name. It sort of suggests that they are inherently aggressive, and they’re not. They’re just vigorously defensive.

IRA FLATOW: That’s good to hear. Before you found the nest, how many sightings had there been of these hornets in the Pacific Northwest?

CHRIS LOONEY: I’m embarrassed to say I’m not 100% positive, but around a dozen to 20.

IRA FLATOW: Oh, that many.

CHRIS LOONEY: And that’s over two years. Yeah, yeah, they really started ramping up in the last month. We got some photographs. There was a doorbell cam, this fantastic video. We picked up a few more in our traps. So it’s funny you say, that many. To me, I’m like, 20 is so low. We should be seeing more. How are going to find them?

IRA FLATOW: [LAUGHS] What, do you suspect you will find more?

CHRIS LOONEY: Yeah. Maybe not many more this year, although we’re changing our traps to some of the stuff that Jackie has provided that seems to be working a little bit better. So we might, but if not this year, definitely next year. And interesting point– British Columbia just collected their second one of the season just the other day.

IRA FLATOW: There we go, our Canadian neighbors helping us out. What do we know about sightings outside of Washington? Do we know just this British Columbia sighting?

CHRIS LOONEY: A couple of British Columbia sightings. So there is a photograph in White Rock, which is the town that basically right over the border from Blaine. There was a specimen found right on the border close to where we eradicated this nest. And then this last one was found a little bit farther northeast of there, which nobody was excited to find in terms of where it was. And also, there was a queen found in Langley, I think, British Columbia this spring.

IRA FLATOW: Do we know how they got to the Pacific Northwest?

CHRIS LOONEY: Absolutely not.

IRA FLATOW: OK, there you have it.


CHRIS LOONEY: Nah, mic drop. Now we suspect that they came on cargo. It’s funny. Really, the only life stage of this that could be easily transported in such a way that it might be able to start a new population are these overwintering fertilized queens. And it only takes one.

So even though they don’t habitually overwinter in the kind of stuff that we would move back and forth across the ocean– you know, they normally overwinter in soil or maybe straw heaps– it’s possible that one was in a cargo ship, and that’s how it got here. That is the most likely explanation. And with as much international cargo as we have, it doesn’t actually take that many propagules to get a chance at getting across the ocean.

IRA FLATOW: And the potential attack on bee populations, is that really what we are worried most about?

CHRIS LOONEY: It is, yeah. That’s what we’re most worried about, and it is kind of the impetus for all of the funding that we’re receiving to try and keep this from establishing. So we’re concerned that it might have impacts on the native ecosystem by eating up all kinds of bugs and changing the balance of species.

And we’re concerned that it’ll have agricultural impacts because they are, of course, known predators of bees. And while they haven’t decimated beekeeping in their native range, they’re certainly something beekeepers always have to mess about with. And we just sort of like to give our beekeepers a break and keep them from having to deal with it.

IRA FLATOW: Give us a description because the hornets look kind of interesting. I mean, and they actually look kind of pretty.

CHRIS LOONEY: Yeah, I’ve been watching them sitting here in my lab for a couple of days. They’re all dead now. But for a couple of days, I had them alive, and they’re stunning. I mean, they’re large enough that you can really see their behavior and maybe relate to them in a way that you can’t smaller insects. They’re maybe an inch to two inches long, depending on which caste you’re looking at, whether it’s a worker or a queen.

They can be pretty thick. They have these really sort of pleasing orange-ish yellow head and stripes and big obvious black eyes. They’re larger than any native yellow jacket and larger than the other hornet we have in North America, which is an introduction from Europe, so the European hornet– which is not on the west coast. It’s back east.

IRA FLATOW: Jackie, I want to talk about the work you’ve been doing over the past few months. It’s my understanding that you’re part of the Hornet Trap A Team. Why are you using traps? To kill these hornets or to catch them alive?

JACQUELINE SERRANO: Well, actually, we’re doing both. So part of the approach that we’re taking is to first detect these hornets throughout Whatcom County, where they had been detected in the previous year. And so the first sort of idea we want to get is, where are these hornets located within the county? And we can do that by trapping them and essentially killing them in a trap. However, our goal now is to hopefully use live hornets to track back to a nest, like we were able to successfully do just a couple weeks ago.

IRA FLATOW: Do you have a special bait that the hornets particularly like?

JACQUELINE SERRANO: Well, so far, it seems like there is one particular bait, if you will, that I have provided to the WSDA. And that is made up of two compounds. One is acetic acid, and the other is isobutanol. But throughout this whole season, since early spring, we’ve been testing other combinations of compounds as well. Because there are so many things that we just don’t know about how these hornets are going to be attracted to these compounds.

CHRIS LOONEY: And to follow up, though, the majority of the trapping we’re doing in the landscape to detect these initially is not the lures Jackie has provided. We just kind of got turned onto those recently because an experiment she and I have been running out in the field. Mostly, it’s actually orange juice and rice wine that we’ve put everywhere. That’s what our citizen scientists were using, too.

So there are sort of two things going on here, this cottage industry sort of trapping bait that we can afford to deploy at a large scale right now, and then this specific work Jackie and I have been doing with these other baits, one of which seems to be a lot more effective.

IRA FLATOW: Yeah. Is there a risk when you set a trap that you’re trapping the wrong things, that native pollinators may get into the trap? And how do you avoid that?

CHRIS LOONEY: So we weren’t sure if we could avoid it. So one of the things we made a commitment to this year is to analyze the bycatch. That’s what we call that, when you catch something you don’t intend to, just like when you kill a dolphin or a turtle in a fishing net, right? That’s bycatch.

And we wanted to analyze the bycatch from all of the traps in Washington state, all of the ones that we placed as an agency, and then these other 1,500 or so citizen science traps. To some level, I try to do exactly that. Are we killing pollinators? Because that would be deeply ironic if we were just removing pollinators from the whole landscape and to see what else is happening.

The good news is, we seem to kill very, very few bees. We’ve processed over 10,000 traps so far, and we just have a handful of bees. When they’re honeybees, it’s usually because somebody has placed the trap right by an apiary. But when they’re kind of far away where the bees don’t necessarily blunder into them, it looks like a no go. We’re catching tons and tons of yellow jackets. There’ll be hundreds and hundreds of yellow jackets in just one of these bottle traps.

And then other things like some moths have been blundering into them. Mostly, they look like an introduced moth, so I guess we can feel a little bit better about that. And then, man, you would not believe millions of fruit flies. So many fruit flies, especially at the end of the season, that these become a solid mass. It is no longer a liquid trap. It is a pile of fruit fly corpses.

IRA FLATOW: Wow. Very, very fascinating. How did you find that first nest that you eventually took out? Did you stumble on it? Did you have some methodology here?

CHRIS LOONEY: Well, so like Jackie said, we had defaulted to using some live traps once we started to have a place– I keep calling it hornet central, but once we had a place where there were lots of hornets. And this is where those isobutanol lures that Jackie whipped up seemed to really be effective. We caught two hornets in a live trap.

And then we caught three more in one of the kill traps baited with that, two of them just that morning. So we were actually able to pull them out and give them a little resuscitation and keep them alive. And then actually, we had tried this earlier with some that a homeowner had netted. Anyway, we basically captured them. We anesthetized them on ice. It gives us time to work with them without getting stung. And we tied our radio tag to it.

The radio tags were provided by another Department of Agriculture Research group, federal researchers working on spotted lantern fly in Pennsylvania. They were looking at flight patterns with them. And we were able to use it and simply track it back, just like you would with a wolf and a radio collar, kind of.

IRA FLATOW: Exciting day or just another day on the job?

CHRIS LOONEY: Super exciting for a couple of reasons. One, we’re walking around. We don’t have our special hornet suits on, right? Because you can’t do anything in those, except fall down a lot. And we’re walking around in the woods, listening to this thing get louder and louder and louder, fully expecting any minute hornets to come boiling out of the ground and us to throttle down and run away.

And we got to a place where it couldn’t be any louder, and it seemed clear that they were in this tree. And I was super bummed because I assumed that the wasp we were tracking just went up to the tree and died or was sitting there. That’s when my boss, [INAUDIBLE], realized they were actually flying in and out of a crack in the tree. We’d been looking at the ground the whole time. So yeah, it was exciting, a little nerve-wracking.

IRA FLATOW: Chris, on the day of this nest extraction, you were vacuuming hornets out of a tree. What the heck was that experience like?

CHRIS LOONEY: At that point, it was just getting tedious because not only did they not come bubbling out of the ground when we got close to the nest, they wouldn’t come bubbling out of this darn tree. Standing up there in this awkward suit in the dark with my red light, pounding on the– I’m not pounding on the tree. Somebody else is pounding on the tree, and I’m holding this vacuum in and seeing them crawl out one by one by one. It took quite a while to vacuum up the– we caught 87 hornets or something like that day. By the time we were getting to the end, I just wanted them to attack already, get it over with.

IRA FLATOW: Really? You were expecting an attack?

CHRIS LOONEY: I was, yeah. They keep those nests pretty warm. So even though it was cold outside, they should’ve been warm inside and ready to defend. And they seemed like they were ready to defend, but in a really lackadaisical way.

IRA FLATOW: So do you wear a special suit, like a space suit or something, not your traditional bee suit?

CHRIS LOONEY: We were wearing these kind of crazy space suits. The hornet has a stinger that’s a quarter of an inch long. It’ll go right through the heavy canvas that these suits are typically made of. So we were kind of scrambling around. And our safety committee, who was excited to buy a thing that contributed immediately to safety, got these hornet suits for us from Amazon.

And they were made of a thick mesh that designed to keep the stinger away and actually maybe kind of locks the stinger up by these two different mesh layers rubbing on each other. They’re awkward to get in and out of. We don’t really have a very good range mobility in them. The face shield presses up against your face, which seems to really defeat the point. So there are some drawbacks to the suits, but we wore them just to make sure. And I’m sure you’ve seen the pictures. They do indeed look like kind of space suits from an older bad science fiction movie.

IRA FLATOW: I’m Ira Flatow, and this is Science Friday from WNYC Studios, talking about the first Asian giant hornet nest discovered in the US. It has since been destroyed. With my guest, Chris Looney, entomologist with the Washington State Department of Agriculture in Olympia, and Jackie Serrano, research entomologist for the USDA in Wapato, Washington. So you take the nest out. And what do you do with all the residents and the nest itself?

CHRIS LOONEY: They are pretty much all dead, except for some that Jackie is maybe still working with, if she’s able to keep them going. They’re more fragile than you think sometimes. They are being dispersed to different researchers. We have Jackie’s group looking at pheromones, another group working on pheromones. People are looking at the genome. A research group in Beltsville will be looking at some for viruses and diseases that might be transmitted to bees. Since these prey on bees, they’re going to come in contact with them a lot.

I weighed and measured all the remainder of these hornets, preserved as many of the larvae as we could, and most of this will, at this time, go back to the landowner ultimately. They sort of fall through a special legal loophole right now that doesn’t prevent anybody from owning them. And they’re not clearly property of the state. So these will go back to that landowner for his preservation. And then, obviously, some will go into museums, too.

IRA FLATOW: So what would be the most helpful or important piece of information for you to have right now about these hornets and what they’re doing here?

CHRIS LOONEY: How far do queens disperse? How far are they going right now when they leave the nest? And then how far do they disperse again in the spring? Those are two sort of critical things that we don’t know that can help us plan what we’re doing on the ground.

And then the other one is the work Jackie’s doing. What can we come up with that is irresistible to them so we can trap them at really low densities? Even if we think there’s multiple nests, there’s certainly not anything close to their sort of capacity on this landscape. And so, we’re trying to trap them with things that are competing with every other thing that might interest a hornet. We just need the best hornet lure money can buy and science can make.


IRA FLATOW: Jackie, are you working on one of those?

JACQUELINE SERRANO: That’s the plan. So one of the things that Chris mentioned is, we want to specifically target the hornets. What is the best attractant for them? The lures that I’m providing right now are kind of more of a general attractant used for other wasps as well, and including your yellow jackets that you find as well. So my goal is to see if I can come up with something that will not only trap just the Asian giant hornet, but trap them in large numbers as well. And that’s sort of my overall goal and contribution for WSDA.

IRA FLATOW: Are you looking for help from our 2 million listeners at all to see if they spot any? Or is it so specialized you don’t think they could be helpful?

CHRIS LOONEY: They could absolutely be helpful with one caveat. If you are not in Washington state or British Columbia, it is incredibly, incredibly unlikely that you’re going to be seeing one. So don’t freak out. And also, don’t call us. I had somebody call today from Florida. Delightful conversation, but realistically, I can’t get on a plane and go to Florida and do anything about it. It would be better to talk to your local Department of Agriculture.

But yeah, if you’re in Washington state or British Columbia, we have a whole bunch of different ways people can contact us. We have a website where they can put up sightings. We had about 5,000, I think, by now. Of course, only 12 of those or so were legit. We have a hotline, an email, and just several different ways people can contact us.

And this nest we took out, it is entirely likely we would never have found it if a nearby homeowner hadn’t said, oh, yeah, this looks like one of those things. We should let them know. And it turned out to be a really good relationship. That’s what got that particular site rolling. We need the eyes of the public on this. And this thing is pretty easy to recognize, so I think it’s a good one for everybody to get involved with.

IRA FLATOW: I want to thank both of you for taking the time to enlighten us about these. We’ll just have to share the adventure with you as you guys move along. Dr. Chris Looney, an entomologist for the Washington State Department of Agriculture in Olympia, Dr. Jacqueline Serrano, research entomologist for the USDA in Wapato, Washington. Thank you both for taking the time to be with us today.

JACQUELINE SERRANO: Of course, thank you for the opportunity.

CHRIS LOONEY: Yeah, my pleasure. Nice being here.

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