The Northern Giant Hornet (NGH, Vespa mandarina) previously called “Asian Giant Hornet,” and “Murder Hornet”) is indeed a giant, being the largest hornet in the world, measuring up to 2.2 inches. Native to Asia from India to Japan, the NGH made its first appearance in North America in 2019 when a bee keeper found one attacking his bee hives in Nanaimo, British Columbia on the southeastern coast of Vancouver Island. A nest was found in a park nearby and it was destroyed. Subsequently others were found in White Rock area of southern BC adjacent to the US border.
The first specimen (2019) and the first nest (2020) in the US were then found in Blaine WA, Whatcom County, just south of the Canadian border. There a beekeeper noticed hundreds of dead and headless bees around his hives and contacted the Washington State Department of Agriculture (WSDA) with documented samples.
The big hornets appeared to be on the move south. The hunt was on.
Through the Summer and Fall of 2020 and 2021 4 nests/hives were found and eradicated by the WSDA, all within five miles of the border and within 10 miles of one another. I’ll describe the detection and eradication process shortly.
My involvement began in the Spring of 2020 when the Whatcom Land Trust with which I volunteer, signed on with the State Department of Agriculture to enlist citizen scientist volunteers to set and monitor traps in hopes of capturing NGHs and tracking them back to their nests. I live in Bellingham, about 20 miles south of the border. I am just finishing my third season monitoring a trap on the 17 acre forest plot that I steward for the land trust. This year (2022) there are about 1,361 traps being monitored throughout the County by the state, the USDA, the County and us volunteers.
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Why all the concern with a pesky hornet?
Concerns of the NGH spreading are due to the potential economic and health consequences. They have been an ongoing concern in various parts of Asia with considerable focus on Japan and South Korea as they too require honey bees for pollination of their plants. The WSDA is currently collaborating with South Korean entomologists in studying how best to manage these critters and protect their honey bees. The NGHs seem to have an affinity for honey bees with their concentrated populations in hives.
The NGH can totally destroy a honey bee hive in a couple of hours. This is significant in that a given hive can hold up to 45,000 bees. (that’s a lot of blossoms not pollenated.) Were these hornets to run free, they could devastate the local and regional pollination of fruit and berry crops. Whatcom County is the number one raspberry producing county in the US while the State as a whole produces 85% of all raspberries. The state also produces 50% of the US blue berries and is 6th in strawberry production. Few of us would want to lose those berries. Elsewhere in the state WA grows nearly 60% of the US apples and a substantial percentage of cherries, all of which are pollenated by commercial bee hives. The loss or even a significant diminution of these crops which collectively run into he billions of dollars, would affect the State’s economy. Further, were these hornets to spread beyond our state into Oregon and California, the fruit and nut crops among so many other bee-dependent crops would suffer greatly. Bees already have major adversaries leading to Colony Collapse Disorder. Adding a new adversary would likely be devastating.
Although the moniker “Murder Hornet” is a little hyperbolic, there are indeed health consequences from these gargantuan insects. Stings from these critters can be lethal. Like other stinging insects, the NGH’s venom can trigger allergic reactions such a anaphylaxis, which if untreated can be fatal. And most people do not know if they are susceptible to having an allergic reaction to the NGH as it is not the same as with other stinging insects such as bees. If one is not allergic to bee stings, they might or might not be allergic to the NGH. Further, due to their size, particularly their longer stinger and the fact that they can sting multiple times, they can deliver large quantities of venom in a short time. And their potent venom causes necrosis around the sting. Further, they can also spray their venom which is hazardous to one’s eyes.
With a potent stinger, the hornet can be a public health threat if someone is stung repeatedly, and it is linked to up to 50 deaths a year in Japan.
Being an apex predator, they do not go looking for trouble with humans but attacks are largely in defense of their hives. They hunt largely other insects by biting off their heads and taking the bodies backs to their hive to feed their young. Based on DNA analyses of NGH frass (feces), their local menu consists of several of the insects common here. If a nest were in my area, less than 15 miles from where four nests have been found, they would have a ready source of food. And in fact one specimen was found last year In Bellingham, just a couple of miles from my trap, but fortunately, no nest yet. Below are some of the most frequent critters on their menu that frequented the orange juice/sake cocktail in my plastic jug.
The NGH life cycle:
Understanding the hornet’s life cycle across the months and seasons is crucial to understanding their control. There are critical periods that set the stage for a colony’s continued propagation. If these are interrupted at certain times, they might not be able to become invasive species to your area and impact your native populations.
Adjacent is a circular diagram illustrating their life cycle. As many will note, this is not different from that of other hive insects. I will briefly note some critical periods that are determinative for their ability to create new colonies. This depiction at the right is based on observations conducted in Japan and S. Korea where most of the research has occurred. Given our similar latitudes (Lat ~490 N), it is likely to pertain here as well.
We can start the cycle in mid winter, January as the new queens go underground to overwinter. A month or so later, the Queens emerge from their hole and search for a suitable spot for their new nest, typically in the ground or the base of a tree. Once settled, she lays eggs into April. The first offspring to emerge are the workers. They are sterile females who continue to build the colony through May and June.
During the mid to late summer the colony is mature and viable. The founding queens lay eggs that will become new virgin queens and males. Workers hunt aggressively to feed the hungry larva still in the combs. It is at this time that honey bees are vulnerable to NGH. During their “hunting Phase”, the NGHs forage and attack individual bees and other insects and take them back to the colony.
Some times they will enter the so called “Slaughter Phase”, in which the hornets will team up and attack a bee hive. They decapitate the bees, as shown above, leave them in a pile and then aggressively defend the hive as their own. Once they occupy a bee hive, they harvest the bees’ pupa and larvae and feed them to their young.
In the Fall after the males and virgin queens emerge, they mate, setting up a new crop of fertile queens, each to found a new nest the following spring. (Finding the nest before the newly fertilized queens can escape is critical to stopping their continued infiltration into the area. ) After serving their respective purposes of maintaining or setting up the next generation, the males and workers die. Queens find a suitable place to hole up through January before they emerge to start the process again.
How were our invasive NGHs found and eradicated ?
As noted above, the first NGHs arrived in southern BC in 2019 and then assumedly moved south into the US in border town of Blaine in northern Whatcom County. The Washington State Department of Agriculture, (WSDA) pest control unit got on the issue immediately and set out to trap them in hopes of finding a live one that could lead them back their nest. They geared up in the early spring of 2020 when queens would be expected to emerge from their hibernation and begin setting up new hives.
It was at this time (April 2020) that the name, “Murder Hornet” came into our lexicons as described in the quote below:
The New York Times accompanied WSDA on an experimental trapping trip in April, which resulted in a story that ran in the news on May 2nd. The title of the story used the term ‘murder hornet’ to describe the Asian giant hornet. Over the next week, the Asian giant hornet story became national and then international news. Thousands of reports of suspected Asian giant hornets flooded in to WSDA as well as every other state’s department of agriculture and entomologists throughout the country.
After several attempts to find an effective trapping procedure, the WSDA found an attractive bait
combination that had worked well in Japan — A plastic bottle containing 8 oz. of orange juice with 8oz. of rice cooking wine. Flaps were cut out of the bottle for hornet entry.
By summer 2020, They were all geared up for a frontal assault on the NGH having enlisted the USDA, Bee keepers and had outfitted 700 citizen scientists who monitored traps in the area where they had been spotted. Through the summer several hornets were trapped, including a queen, a male and a worker, mostly centered around Custer and Birch Bay, just south of Blaine and the BC border. Their goal was to capture a live one that they could tag with a radio transmitter and have it lead them to the nest.
At the end of September, they caught a live one in a butterfly net and attempted to tag it. They tried attaching the transmitter with super glue and double sided tape. The hornet could not fly with these adhesives.
Then in early October, 2020 they captured another one and after some technical glitches, they were able to secure the transmitter to the hornet with dental floss.
After release into an apple tree, they followed the hornet for an hour before the signal was lost.
Finally, two weeks later, they captured several new hornets, tagged and successfully followed them to their nest in a dead alder tree.
The entry was at the base of a tree but the combs were located up to 10 feet high into the tree cavity.
The team dressed in heavy protective gear, wrapped the tree in plastic to prevent escape and attempted to vacuum out the hornets.
Knowing they did not get them all, they then used CO2 fire extinguisher to anesthetize or kill the remainder. Following these extraction procedures they cut the tree down and extracted six combs containing 108 white-capped cells with pupae and 6 unhatched eggs. There were 190 larvae, 9 adult males, 76 queens, and 26 workers in addition to the 85 previously removed from the tree with the vacuum.
Spring 2021 started with a full push to find and trap any queens that might have escaped in the fall before they had a chance to lay eggs and establish a new colony. The WSDA, along with the USDA, local bee keepers, and citizen volunteers, set hundreds of traps again throughout the county, concentrating on the areas around where the first ones were located.
It was not until mid August that they tracked a hornet to a second nest and followed the same eradication procedure as the year before. From this nest they extracted 1,474 specimens at various stages of development and a single queen.
Within the next month, two more nests were found from which they extracted 449 and 777 specimens, each with a single queen. The timing was probably good as it was toward the end of September, when adult males would begin mating with virgin queens and setting the stage for another whole crop of potential nest builders for the following year.
Is the Case now Closed?
No, the case is not yet closed. The WSDA pest control team will remain vigilante with trapping for the next two years as they can not declare eradication until they have gone a full three years with no sightings.
There remains a couple of enigmas in this case:
1. How did get here? Certainly they did not fly as their know travel distance has been determined to five miles. Currently the main hypothesis is that they hitched a ride on a cargo ship from Asia which is the most likely route, but:
2. mitochondrial DNA analyses of these first specimens from the US and from Canada were compared with NGHs from Korea and from Japan. The results are puzzling and suggested that those found in the US were not of the same lineage as those from Canada:
While the Washington state specimen shared 99.5 percent of its mitochondrial DNA with the one from South Korea, the Canadian and Japanese specimens shared a bit more than 60 percent of their DNA. Lead author Telissa Wilson, with the Washington State Department of Agriculture, writes in an email, “We were all surprised that the U.S. and Canada samples were from different lineages when the locations were in such close proximity.”
Do the Canadian and US samples represent two separate migrations?
Stay tuned...
A sight that we do not want to see in 2023
If you have not had enough NGH information and have an extra 14 minutes to spend, check out the following documentary video that was made by TVWashington in 2020 to illustrate the history and processes covered in the above bucket.