‘Murder hornets’ have arrived in the U.S.

May 4, 2020

Two unusual hornets—striking, with orange and black markings and long stingers—were spotted near Blaine, Washington, in late 2019. Subsequent investigation revealed they were Asian giant hornets, the world’s largest wasps, growing nearly two inches in length.

Scientists are concerned that these hornets could spread throughout Washington State and beyond, presenting a danger to U.S. bees—which are already in decline—and humans.

Nobody knows how the insects arrived in the United States. But the discoveries set off alarms and the insects began trending on social media as “murder hornets.” These predators, native to East Asia and Japan, are infamous for decimating honeybee colonies.

With the toxic venom that their large stingers deliver, the insects already are known for killing people in their native habitats: In Japan, an average of 30 to 50 people each year die from the hornets’ stings. In 2013, when populations of the hornets were unusually high, they killed 42 people in a single Chinese province. Most serious incidents occur when people come near or disturb the insects’ hives.

These insects “are pretty formidable,” says Chris Looney, an entomologist at the Washington State Department of Agriculture. “I am very worried.”

At the same time, Looney offers some caution, starting with the nickname “murder hornet.” He hadn’t heard it before recent press coverage of the insects—and he doesn’t love it.

“I worry people are already scared enough of insects for dubious reasons,” Looney says. But he grants that there’s an upside to the ominous label: “It does seem to have gotten people’s attention. I just hope the sensational ‘murder hornet’ coverage helps us understand our ecosystems a little better.”

Voracious feeders

As of now, researchers can’t confirm how the hornets arrived. Looney says it’s most likely they got accidentally trapped in shipping containers from one of the countries where they’re native.

One complete hive of the insects was found and destroyed in late 2019 in nearby Nanaimo, Canada. But genetic tests suggest those giant hornets were introduced separately.

Asian giant hornets from Japan and East Asia already have established themselves as invasive species in other nations, such as South Korea. These social wasps form colonies, comprising one queen and many workers, which can fly half a dozen miles or more from the hive to find food. They eat many kinds of insects, but they seem to especially enjoy feasting on bees.

When they encounter honeybees, their attack starts with a “slaughter phase” in which they serially bite the heads off bees with their large mandibles, Looney explains. Within 90 minutes, a small group of Asian hornets can destroy an entire colony’s workers this way, he says.

Then, the hornets shift to feeding. They occupy the honeybee nest for up to a week or longer, feeding on the pupae and larvae. They then feed it to their own young.

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