On December 8, 2019, a Blaine resident finds an unusually large dead hornet in his yard and calls the Washington State Department of Agriculture (WSDA). He also reports having seen a live hornet at his hummingbird feeder. Staff from the WSDA retrieve the insect and confirm its species as Vespa mandarinia, the Asian Giant Hornet -- known informally as the Murder Wasp, Yak Killer, or Murder Hornet. The WSDA has been on the lookout since a nest was found (and destroyed) in Nanaimo, British Columbia, in August 2019. The arrival of V. mandarinia creates consternation. Not only is it alarming looking -- up to two inches long, with powerful mandibles and a quarter-inch barbed stinger -- but it is an aggressive predator to honeybees and its stings can be dangerous to humans. One domestic beehive in Custer, Washington, near Blaine, was found destroyed in November 2019, in what is later assumed to be an Asian Giant Hornet attack. Regional beekeepers and other volunteers collaborate with the Department of Agriculture to monitor and attempt to eliminate the newcomers.
An Efficient Predator
V. mandarinia are native to Asia, ranging from India, South China, and Japan to the Korean Peninsula. Primarily residents of forested areas near sea level, they attack both wild and domesticated bees and hives, killing and eating both adults and larva, and also consuming the honey. They prefer to nest in hollows in the ground, often at the base of trees. In the spring, mated queens who have been dormant over the winter will emerge to feed on tree sap before excavating a nest and beginning to lay eggs. When the first foraging wasps mature and emerge from the nests, usually around July, scouts head out to locate beehives and mark them with pheromones. Other wasps from that nest follow the scent trail and attack the hives. A group of a dozen to 20 hornets can destroy a hive in an hour.
When the slaughter is complete, the hornets roll the corpses into ball-shaped clumps and carry them to their nest to feed the larvae, which in turn secrete a gooey substance that is eaten by the adults. Strong and fast flyers, the hornets can travel at least five miles in search of prey.
Asian beekeepers have developed a number of strategies to protect their bees. The simplest is to station people around the hives to beat the attackers with sticks. Other methods include traps baited with fermented rice wine and screens over the hives to prevent entrance. None are fully effective. The Asian honeybee, which is a different species than the European honeybee used in North American apiaries, has itself developed a defense. When a hornet scout appears at the hive, a few hundred bees will emerge and surround it, forming a buzzing, vibrating ball that over about an hour can achieve and maintain an internal temperature of 115 degrees farenheit. That is enough to kill the wasp while allowing the bees, at least most of them, to survive. The hive is then safe until the next scout finds it. Domestic honeybees in the United States and Canada do not have this adaptation.
Humans themselves are the species' only predator. Many hornets are killed by beekeepers, and many more are killed in the quest for specialty cuisine, especially in the central Japanese region of Chibu. Grubs are fried or steamed, while the adults are skewered like kabobs or drowned in a distilled liquor called shochu, adding a tingling kick to the drink. Wasp hunters wear elaborate protective gear, including solid face helmets with a fan inside, and suits with a slick outer fabric covering a foam core, as traditional beekeepers' costumes are not enough to repel the quarter-inch-long stingers. In Washington, the state department of agriculture acquired a batch of these suits to use in eradicating nests.
An Unknown Journey
The first nest found in North America was in Robins Park in Nanaimo, British Columbia, on Vancouver Island. Local beekeepers used location data from a hornet sighting in July and picked the park as a likely site. Although it was just five feet from a public walking trail, no one was bothered until John and Moufida Holubeshen identified it in August. John was stung on approach to the nest, saying the size and velocity of the attacker made it feel like getting hit in the chest with a plank of wood. The pain, which he said felt like a badly bruised rib, lasted 16 hours. Nevertheless, the Holubeshens returned the next night with two other beekeepers and destroyed the nest. The next confirmed North American sighting was made soon after, via photograph, in White Rock, B.C., just north of the U.S. border.
The first U.S. report of the hornets in the wild was from Blaine, where a resident walked outside on December 8, 2019 and saw an unfamiliar creature on his doorstep. "It looks like a toy," said WSDA entomologist Sven-Eric Spichiger. "It's a freakishly large hornet with a giant head." The man posted a photo of the dead vespa on Reddit and was contacted by the state Department of Agriculture the next day. Workers drove up from Olympia that week to collect it. By December 14 the state office received official confirmation from the USDA of the unwelcome U.S. first. That identification in Blaine solved a mystery for Ted McFall, a longtime beekeeper in nearby Custer, who had found one of his hives destroyed the previous month. On a routine check, he saw "thousands of bee bodies strewn on the ground outside of the hive" (Baker, "The Arrival ..."). Inside the hive was more carnage, piles of decapitated bees, and no survivors. McFall said it was the first time in his experience that his bees had been unable to mount even a token defense. Not a single dead attacker was visible.
The hornet's route to North America is unknown. Only a queen could establish a new hive on a new continent, and queens are active outside their nests for only a fairly brief period. One theory is that hornet queens in Asia have settled in shipping containers for their winter dormancy and then awakened across the ocean. One mated queen can establish an entire colony, and that colony would produce more queens to continue the advance. Another possible transmission route is through the shipping of live larvae for aficionados of wasps as food or as traditional medicine. This is illegal but not unknown. A package containing an entire V. mandarinia nest, including live larvae and pupae, was intercepted at a U.S. port of entry at some point before 2010, according to Allen Smith-Pardo, an entomologist with the USDA.
"This is Our Window"
However they got here, once they were spotted, the Department of Agriculture and regional beekeepers mounted reporting and tracking systems to monitor the spread and, if possible, eliminate the hornets.
"This is our window to keep it from establishing," Chris Looney, an entomologist with the Washington State Department of Agriculture, told The New York Times (Baker, "Murder Hornets..."). "If we can't do it in the next couple of years, it probably can't be done." Distribution modeling done at Washington State University suggested that much of Western Washington and in fact much of North America is good V. mandarinia habitat, and residents nationwide began looking at all kinds of flying insects with more alarm than usual. An interactive map posted on the Washington State Department of Agriculture website garnered dozens of reported sightings around Western Washington and Oregon within a few weeks, none of which had been verified as Vespa mandarinia as of May 7, 2020.
Somewhat similar-looking native species including yellow jackets, native elm sawflies, bumblebees, and cicada killer wasps all led to reports that were dutifully recorded on the map. The hornets became instant media celebrities, sparking the creation of memes and jokes pairing them with another notorious 2020 newcomer, the coronavirus causing COVID-19.
In addition to the public reporting system, the WSDA along with beekeepers associations and other volunteers began more formal tracking methods in early 2020. These included "sap traps," squares of sticky material placed on sap-producing trees in April, in the hopes of trapping queens as they stocked up on nutrients before descending into their nests to start laying eggs. Since only the queens are out during this period, the chance of capture is slim but the potential payoff is great. Killing a queen dooms an entire colony.
Once enough workers have hatched and matured enough to emerge and begin predation, traps baited with a mixture of orange juice and rice cooking wine are placed around apiaries and likely nest sites. The WSDA recruits volunteers to make and monitor traps anywhere in the state, but particularly in the Northwest Washington counties of Whatcom, Skagit, Island, San Juan, Clallam, and Jefferson. Thirty-eight apiaries in Whatcom County alone, spearheaded by the Mount Baker Beekeepers Association, had joined the effort to track and eliminate the invader. Other monitoring efforts involve radio-tagging live-captured wasps in order to track them back to the nest area, and using thermography sensors to locate underground nests by their heat differential to the outside air, especially at night.
Spichiger said he was concerned about potential harm to forest hikers and mushroom hunters, and to farmers and road maintenance people who may disturb nests along the margins of wooded areas. A farmer near the site of the honeybee hive attack in December 2019 reported that a massive hornet with a distinctive yellow head repeatedly attacked the cab of his tractor as he worked a field near the woods. He could see its stinger banging on the windshield. Vespa mandarinia kill 50 to 60 people a year in Japan. Although the large majority of people stung survive, they can suffer injuries ranging from pitted scars caused by necrotic tissue at the sting site to kidney failure requiring dialysis.
While Washington residents and researchers spread warnings about the threat to people and honeybees, scientists farther away reminded Americans that other nations have co-existed with the hornets for centuries. University of Illinois entomologist May Berenbaum told The Associated Press science writer Seth Borenstein that "people are afraid of the wrong thing. ... If anyone's a murder insect, it would be a mosquito." Berenbaum chalked up some of the concern over the hornets to the trauma of the coronavirus pandemic. "This year is unbelievable in a horrible, horrible way. Why shouldn't there be murder hornets?" she said (Borenstein).