For the first time in the United States, scientists have discovered a live nest of invasive Asian giant hornets, sometimes known as “murder hornets.”
Washington State entomologists plan to destroy the nest, which was found October 22 in a tree in the town of Blaine, in the far northwestern corner of the state.
The discovery is an important milestone in the effort to prevent the species—the world's largest wasps—from becoming established in the Pacific Northwest, scientists say.
“We're very pleased to tell you that we did get to [a nest],” said state entomologist Sven Spichiger, at a Friday press conference. Until the nest was found, Spichiger said, scientists weren’t sure if their techniques to track the hornets would work in the region’s densely wooded terrain.
The invasive insects were first seen in the state in fall 2019, and their arrival set off alarm bells. Voracious predators that are particularly deadly to honeybees, Asian giant hornets have the potential to expand throughout the state and possibly the West Coast, says Chris Looney, also an entomologist with the state.
To stop the insects' spread, killing individual workers is useless, says Looney. So state scientists and collaborators have set thousands of traps around northwestern Washington, in hopes of catching live insects that can be tracked back to their hives.
In this case, on October 21 and 22 trappers collected four live worker hornets from bottles to which they’d been drawn by bait. Scientists then outfitted three of the female worker hornets with radio-frequency trackers, and one of the hornets led the scientists to the nest. Though the hornets usually nest in the ground, this nest was located in a tree on private property.
The hornet that led trappers to the nest first flew around for about an hour before resting on a leaf. The scientists placed her on a table and fed her some grape jelly, “which seemed to revive her,” Spichiger says. They then tracked her a few hundred yards into the woods and heard buzzing that led them to the hive.
Scientists first knew that the hornets had survived the winter when three queens were discovered in late spring. Since mid-summer, several hornets have been trapped at a couple locations in the same region of the state. Finding those hornets confirmed that queens had successfully reproduced from at least one initial nest formed in late 2019, and had created new nests.
How many more?
There are almost certainly more hives yet to be found, Spichiger says. Hornet sightings also have been confirmed in another area in Blaine—far enough to be from a different nest—and near the town of Birch Bay.
Scientists will continue improving their traps and monitoring them, he says. If they find more live workers, they will repeat the tagging and tracking in hopes of following them to their nests.
Spichiger says it’s possible, though unlikely, that this nest could have already produced queens that may have dispersed. That makes its destruction an urgent matter, he says: “Once we know we have one, we should shut it down immediately.”
Though workers die over the winter, any new queens that reproduce and disperse can form new colonies next spring—which is what scientists are trying to prevent. Nests can contain up to around 800 workers and produce a couple hundred queens.
Though news of so-called “murder hornets” has spread across the country, the insects themselves are still limited to northwestern Washington, scientists emphasize. The hornets do pose a serious risk to honeybees and native bees if they become established and spread, but that’s not a cause for panic, Looney says.
After the news about the insects broke in May, alleged sightings of the species spiked as did searches for hornet-killing pesticides. But that kind of disproportionate reaction is worrisome, he says, because it can lead to the killing of innocent pollinators. (Read more: 'Murder hornet' mania highlights dangers of fearing insects and spiders.)
“In general, the public doesn’t need to be worried” about attacks from these hornets, Spichiger says. They mainly attack only when people approach their nests.
When that happens, though, the insects can sting—and it’s painful.
Because the hornets can spray venom as well as sting, the researchers who hunt and handle them will be wearing eye protection and other protective gear, Spichiger says.
Though there’s much more work to be done, Spichiger says, scientists do have a chance to prevent the species from establishing a long-term presence in Washington: “We should be cautiously optimistic that we can eradicate them.”