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Friday, April 19, 2024

Asian giant hornets sighted in US for first time, UC Davis entomologists say media exaggerated severity of issue

Despite sightings of giant hornet species, spread through North America highly unlikely, experts say 

Giant, tiger-striped insects have been making quite the buzz lately. Vespa mandarinia, or the Asian giant hornet, typically lives in eastern and southeastern Asia, but two individuals of the species were sighted in the U.S. for the first time.

The Washington State Department of Agriculture (WSDA) verified two reports of the Asian giant hornets near Blaine, Washington in December of 2019. One report was of a dead hornet, while the other was of one spotted flying back into the forest. Additionally, a giant hornet nest was found and destroyed in a park south of Nanaimo, British Columbia, Canada.

In Washington, neither the second hornet nor its nest were found, but researchers are fairly confident their removal efforts were successful. In April, Blaine local authorities alerted residents to the possible threat and asked them to stay vigilant, according to the WSDA.

“They found a dead individual and were able to confirm that, yes, this is Vespa mandarinia,” said Eleanor Field, a doctoral candidate in entomology from Iowa State. “Then the same resident also said, ‘Hey, I saw another one and it went off into the woods.’ That means we have one confirmed dead individual and another presumed confirmed sighting.”

Although recently introduced potentially invasive species should not be downplayed, many researchers, including Lynn Kimsey, a professor of entomology and director of the Bohart Museum of Entomology, believe the media exaggerated the severity of this issue. 

“[Somebody] at the Associated Press got bored with coronavirus coverage and decided to whip up frenzy on something else, but it’s absolutely ridiculous,” Kimsey said. “This happened almost six months ago. This is old news.”

While nobody knows exactly how these hornets arrived in the west coast, most likely a mated queen was transported via shipping cargo from Asia to the U.S, Kimsey said. 

One possibility is that someone brought a colony to the U.S. to eat the larvae, but that is “less likely,” Kimsey said. While this species is novel to many people in the U.S., these insects are well known in Asian cultures, and their “crunchy” and “very flavorful” larvae are considered a delicacy, Kimsey said. This species has also been well studied by scientists in Asia, especially in Japan. 

“As large and as nasty as these wasps are, they’ve been in China and Taiwan and Korea and Japan for thousands of years cohabitating with people and beekeepers there,” said Douglas Yanega, the senior museum scientist for the Entomology Research Museum at UC Riverside. 

Although the term “murder hornet” has been readily adopted by news outlets, Asian giant hornets present no more of a threat to humans than other species in North America. All hornets will sting intruders multiple times with their straight stingers to defend their hives, Field said. 

“There’s nothing more aggressive about this species that makes it sting multiple times, it’s just physically able to do that,” Field said. “Their venom is a little more potent than honeybee venom, but it’s not the most potent venom. It’s not even the most dangerous hornet of them all.”

Unless individuals have an allergy or receive dozens of stings, stings from these hornets rarely require medical attention, Field said. In Japan, these hornets kill up to 50 people per year, according to The New York Times

“It’s very, very unlikely that a person here in the United States is going to come across these guys,” Field said. “These are big hornets, so you’re probably going to know that they’re there. So, the risk is pretty low for people here in the United States.”

Just because the hornets have been introduced to North America does not mean a population will be successfully established. Many barriers exist for species in new environments, such as surviving new climates and competing with native species, Kimsey said. 

Since hornets are social insects, the survival of their reproducing queen is paramount to a population’s success, Field said. Queens mate in the fall, hibernate through the winter and reemerge to reinstate the population in the spring. The one hornet that escaped in Washington would not be able to survive on its own.

“It takes almost an entire year for [the hornets] to build the colony up before they can produce reproductively,” Yanega said. “If they get intercepted or interrupted anywhere in between, then the whole thing fails.”

Since no individual hornets have been seen thus far in 2020, it is likely that no queen survived through the winter to reestablish a colony, Field said. 

“It doesn’t matter how many males or non reproductive workers survive, you really have to have the mated queen, so that automatically kind of reduces the likelihood of the chances that they successfully survived,” Field said. 

Despite widespread news coverage, only people in Blaine, Washington should be paying attention to the pest watch, Field said. WSDA released a statement regarding the hornet to alert their community, not to cause widespread panic throughout the U.S. 

“For anybody living anywhere else, this is none of your business really, and it shouldn’t affect you and you shouldn’t be thinking about it or worrying about it,” Yanega said. 

One reason for the surge in news stems from the hornets’ large size. As the largest hornet species in the world, adults can be up to two inches long, Kimsey said. 

“People are very excited about their size, but they’re not the only large hornets,” Field said. “There are several other large wasps out there so just seeing something big is not a great indicator that you have this species.” 

While some media outlets have been depicting this hornet species as aggressive and “particularly mean,” many of their behaviors resemble that of other hornets, according to Field. Behaviorally, this species shares characteristics with other social wasps. 

“[Their antivenom stinging mechanism to protect their hive] is not something specific to the species, it’s something that you see across social insects,” Field said. “They’re not meaner than others, they’re just doing their job.” 

The most focused-on behavior of these giant hornets is their predation of honey bees, despite the fact that other insects, like yellow jackets, prey upon them as well. Asian giant hornets have a particularly gruesome way of ambushing a honey bee colony, Field said. After decapitating honey bees, these hornets remove their thoraxes and feed them to their larvae. 

Even though western honey bees are not native to the U.S., they have been living in North American environments for so long that they are now essential agricultural pollinators, said Gigi Melone, a third year entomology major. 

“[Asian giant hornets’] effect would be on the crops that use honey bees to pollinate them,” Field said. “This is a huge, multi billion dollar industry here in the United States so the concern really is economic and less ecological.”

Their gruesome honey bee attacks may be why people use the term “murder hornets” to describe the species. Field said she is unsure how this name originated but guessed that it could have been coined from a translation of a Japanese common name, or by media outlets in the U.S.

“I think they picked [the name] to draw up hysteria and to sensationalize this insect,” Field said. “It was pretty effective at doing that. It’s crazy because they’re not going around murdering people.”

Despite the negative coverage regarding the Asian giant hornet, it always excited Melone to see insects in the news. Both Melone and Field hope the news about the hornets will spike interest in insects. 

“I think if this has made people curious about insects, it’s a great time to start learning about insects, because they’re all around us, especially in spring,” Melone said. 

Written by: Margo Rosenbaum — science@theaggie.org


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