The bad news: they are nicknamed “murder hornets.” The good news: there have only been two confirmed specimens (and four unconfirmed reports) since initial detection in winter 2019. The best news: they are not an invasive species—yet.
There’s no denying the prospect of being stung by a so-called murder hornet is frightening. Humans may be afraid, but it’s the honey bees that should be terrified. The Asian giant hornet, Vespa mandarinia, is a significant predator of honey bees. One hornet can kill dozens of honey bees in just a couple minutes. A group of 10 hornets would be able to decimate a small colony of 10,000 honey bees in less than 1.5 hours.
When we talk about today’s invasive species, it’s most often in the context of what they have managed to kill or alter in our already-established ecosystem. The somewhat-slow arrival of Vespa mandarinia puts us in a unique position to roll back the spread of the hornet before it becomes invasive.
“Before we can roll back the spread we need to determine the extent of the invasion. Finding the extent of the population is the best way to ensure it does not become established,” Tim Lawrence, a Washington State University professor and scientist at the Island County Extension, told Laboratory Equipment. “We need to get the word out there. We need to get a clear image of what’s happening out there, and have people report it as soon as possible.”
Washington State University scientists are asking citizens to be vigilant about Vespa mandarinia sightings in the area. The Washington Invasive Species Council even has a smartphone app to report sightings of all invasive species—WA Invasives.
What makes these hornets different?
The Asian giant hornet is unlike any bee or hornet seen in the U.S. before. In eastern and southwest Asia, it lives in forests and low mountains where it feeds on large insects, including native wasps and bees. It has already devastated the population of European honey bees in Asia. Vespa mandarinia measures 50 mm (2 inches), about 5x the size of a European honey bee, which clocks in at 10 to 15 mm.
“They have about 7 times the amount of venom as the honey bee. Their stinger is ¼-inch in length and they can deliver the sting with 225% more force than the honey bee,” Lawrence said.
In fact, the hornet can sting through most traditional beekeeper suits. Scientists with the Washington State Department of Agriculture (WSDA) had to order special reinforced suits from China. And unlike honey bees, the giant hornet can sting multiple times. Even if someone is not allergic, multiple stings can be fatal due to the hornet’s potent neurotoxin.
What next?
Washington scientists are bracing for the giant hornet’s emergence this spring, when queens emerge from hibernation, feed on plant sap and fruit, and look for an underground dens to build their nests. Once established, colonies grow and send out workers to find food and prey. The hornets are most destructive in the late summer and early fall, when they are on the hunt for sources of protein to raise next year’s queens.
In addition to asking citizens to record any sightings, scientists with the WSDA Pest Program are taking the lead on finding, trapping and eradicating the hornet. They are beginning to set traps for queens now, with a focus on four specific counties in Washington near reported sightings.
“Our focus is on detection and eradication,” said WSDA entomologist Chris Looney.
Honey bees are crucial to the American food supply as farmers rely on them to pollinate important crops. From 2006 to 2013, more than 10 million bee colonies across the world were lost to colony collapse disorder. In the years since, bees have finally started to rebound, with honey-producing colonies in the U.S. increasing 4 percent in 2018. The introduction of a powerful predator could reverse all progress, however.
“Honey bees do not need more pressure on them,” Lawrence said.
Photo: Asian giant hornet, the world's largest species of hornet, was found late last year in northwest Washington. WSU Extension scientists are partnering with state agencies, beekeepers, and citizens to identify and report the invasive insect. Credit: WSDA.