Invasion of the murder hornets
They’ve been in the headlines since last December: “Giant Murder Hornets Arrive in North America”; “Murder Hornet Nest Found in Washington State”; “A Sting that Can Kill.”
They look and act like something out of a science-fiction movie or taken straight out of a Steven King novel. They’re huge. They spit venom. And their stings can be lethal to humans.
Asian giant hornets (AGH), Vespa mandarinia, can grow to be more than 2 inches long. They’re the world’s largest bees. Imagine hornets the size of your thumb, with orange heads, a yellow-striped thorax and ant-like mandibles (mouthparts used for biting, cutting and/or holding food).
In an article written by Seth Truscott, a public relations and communications coordinator for the College of Agricultural, Human, and Natural Resource Sciences at Washington State University, Todd Murray, a WSU Extension entomologist and invasive species specialist, is quoted as saying, “It’s a shockingly large hornet … a health hazard, and more importantly, a significant predator of honeybees.”
One of the key differences between bees and hornets is that bees, as a rule, can sting only once while hornets, including AGH, may sting repeatedly, delivering several times the amount of venom of other bee species. Several times the pain, too. Combine that with the fact that, unlike other hornets, AGH have stingers that can penetrate thick clothing, including standard beekeeper suits. The insect reportedly kills dozens of people in Japan every year, where encounters with them are not that uncommon.
As frightening as that may sound, AGH generally don’t attack people or pets, unless they feel threatened. What’s more, bees (including hornets and wasps) kill an average of 62 people a year in the United States, according to the U.S. Centers for Disease Control and Prevention.
AGH in North America
In September 2019, a ground nest of AGH was discovered near a public footpath in Nanaimo, a city on the east coast of Vancouver Island, in British Columbia, Canada. Fortunately, authorities were able to quickly track down and destroy that nest.
Not long after that however, in December of 2019, the Washington State Department of Agriculture received and verified two reports of AGH in this country near Blaine, Washington (Whatcom County).
Using a network of traps, WSDA staff, with the help of other cooperating agencies and citizen scientists, began diligently tracking sightings. The first trap-catch was made in July of this year. More recently, four hornets were captured in newer, modified traps set by WSDA entomologists. The scientists attached radio trackers to three of the captured hornets before releasing them. The trackers led them to a nest within the cavity of a tree located on private property. On Oct. 24, the nest was successfully eradicated by technicians who used foam to seal access points in the tree trunk before wrapping the trunk in cellophane and then vacuuming the hornets out of the nest, to be destroyed.
These encounters are commonly referred to as the first-ever AGH sightings in North America. However, although it was not highly publicized, the United States had a close call with the hornets in 2016, when an inspector with the U.S. Department of Agriculture Animal and Plant Health Inspection Service flagged an express package that had arrived in San Francisco, California. APHIS entomologist Allan Smith-Pardo, who was charged with identifying suspicious wasps or bees found in cargo or mail, identified the package as a nest of AGH, confirming that “There were no adults in the package, but” there were “plenty of pupae and larvae.” A few were still alive. (“Insect Systematics and Diversity,” Oxford Press, May 2020, page 23)
The real danger
Although the hazard to humans posed by the stings of AGH is real, the hornets are a much greater direct threat to honeybee populations than to people. In late summer and fall, they enter a ferocious slaughter, or bee-killing phase. A small number can completely wipe out an entire honeybee colony in a matter of hours. They literally massacre the adults, decapitating every one of them, and then take the brood — larvae, pupae and honey — to provide food for their young.
Invasive species are organisms that are able to thrive and reproduce in non-native areas to the point where they pose a risk to the existing ecological fabric. AGH are native to temperate and tropical forests of eastern Asia, South Asia and mainland southeast Asia, including parts of Japan, China, India, South Korea, Taiwan, Pakistan, Malaysia, Thailand, Sri Lanka and the Russian far east, where they are also known as Japanese hornets, yak-killer hornets and giant sparrow bees. They now pose a serious threat to Washington state honeybees and the related honeybee industry. A similar hornet in Europe has reduced beehives by 30% and hive-honey yield by up to two-thirds. Preventing the establishment and spread of AGH in North America is critical.
AGH are not present in New York and hopefully won’t be in the future. If you have questions about wasps or any stinging insects, you can contact your local Cornell Cooperative Extension office for advice or to submit samples for identification.