The Asian giant hornet is a big, mean-looking insect with a potent sting. Their queens can grow to be up to two inches long and their quarter-inch stingers can pierce normal beekeeping attire. They are also voracious predators capable of massacring entire honey bee hives in a matter of hours—decapitating thousands of the hive’s adult bees and absconding with the helpless larvae to feed the hornets’ own brood.
As their name suggests, the hornets are native to Asia, but at the tail end of 2019, they were seen in North America for the first time, reports Mike Baker for the New York Times.
The four confirmed sightings of the Asian giant hornet (Vespa mandarinia) in the United States, along with two more in Canada, occurred in 2019 between September and December. The American sightings were all of individual hornets, but in September, a nest was found and destroyed on Vancouver Island, British Columbia, reported Sean Boynton for Global News.
The Times’ coverage was widely shared, causing many in the United States to add invasion of the world’s largest hornet to their growing list of concerns for 2020. But are these so-called "murder hornets," as some researchers call them, really killers? And are they poised to decimate North American honey bees?
“You shouldn’t worry about it,” says Floyd Shockley, the entomology collections manager at the Smithsonian National Museum of Natural History. “More people die of honey bee stings in the U.S. than die annually, globally, from these hornets. About 60 to 80 people die from [allergic] reactions to honey bee stings [in the U.S.]; only about 40 people die per year, in Asia, mostly in Japan, from reactions to the [giant hornet] stings.”
That said, the sting of the Asian giant hornet is far more painful and toxic than that of a honey bee. Researchers have likened the sensation to having a hot nail driven into one’s flesh. However, Shockley says giant hornets are only dangerous if provoked and tend to keep to themselves unless threatened.
In 2013, parts of rural China experienced a notable exception to the hornets’ typical disinterest in humans when swarms killed 42 and injured more than 1,600, reported Madison Park, Dayu Zhang and Elizabeth Landau of CNN at the time. Experts speculated that warmer temperatures had allowed the insects to breed more successfully than usual and that the deaths may have been the result of workers venturing deeper into their forested habitat, reported Tania Branigan of the Guardian in 2013. Local officials advised people to seek medical help if they were stung more than ten times and to treat more than 30 stings as a medical emergency.
Since the hornets were spotted last year, entomologists at Washington State University and the Washington State Department of Agriculture (WSDA) have been preparing to nip this potential invasion in the bud. Asian giant hornets typically hibernate during the winter and emerge again in April, and the researchers spent last month setting traps to locate and eradicate any hives.
“This is our window to keep it from establishing,” Chris Looney, an entomologist with the Washington State Department of Agriculture, tells the Times. “If we can’t do it in the next couple of years, it probably can’t be done.”
Forested, rainy western Washington State closely mimics the species’ preferred habitats in Asia, making the Pacific Northwest an ideal place to establish hives, which are typically found underground.
But Shockley says these isolated reports don’t add up to a full-scale invasion that could endanger U.S. crops anytime soon.
“Is it possible that a few beekeepers are going to lose a few hives? Yes. I can’t rule out that possibility. But is it going to be global devastation? No,” says Shockley. “It’s important to focus on the facts, and the facts don’t support that this is an established invasive that’s going to destroy the North American honey bee industry.”
Part of the vulnerability of U.S. apiaries comes from their use of European honey bees, which are totally defenseless against the giant hornet—their stings can’t even penetrate its thick armor. But in their native land, the hornet’s prey has some fascinating defenses.
If a scout from a giant hornet nest finds a hive of honey bees, it will swoop in to mark the target with a pheromone that attracts its compatriots. But if that hive is full of Japanese honey bees, the bees will play it cool, like nothing untoward is happening, until the hornet enters the hive. Then they will swarm the scout and begin vibrating their wings. The vibrating ball of bees generates enough heat and buildup of carbon dioxide inside the ball that it actually cooks and suffocates the hornet.