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Discover: Look at that face! Fascinating facts about the so-called ‘murder hornet’

We get up close and personal with the Asian giant hornet with help from Guelph entomologist Dr. Gard Otis

When it was reported last week that so-called ‘murder hornets’ had made a home for themselves in B.C., it was the first time many Canadians had been introduced to the Asian giant hornet.

And while they’re certainly off-putting in size and appearance (and for the reputed power of their venom), the world’s largest species of hornet is also a fascinating insect. So, rather than be frightened of them, we reached out to an entomologist to learn more about these interesting creatures.

Gard Otis, a retired professor from the University of Guelph, has spent more than three decades studying honey bee behaviour and ecology. As part of that research, he spent time in Vietnam where he examined the responses of honey bees to attacks by giant Asian hornets (standard nomenclature is “Asian giant hornet”, but Otis prefers “giant Asian hornet.” The same species has a colour form referred to as the “Japanese giant hornet’ as well.)

So when it was reported earlier this month that the giant Asian hornet Vespa mandarinia, which some have dubbed the “murder hornet,” had been discovered in North America, Otis, who is among a handful of North American researchers that have studied these types of hornets up close, was in high demand.

By the time he and I connected by telephone on Friday morning, he had already fielded two dozen media requests in that week alone.

One of the most frequent questions he gets is what he makes of the hornet’s sinister moniker. 

“I’d never heard it before until I saw it in the New York Times,” Otis laughed. “I have a suspicion it was translated from something in Japanese and that was how it came out. As a nickname, I prefer ‘giant sparrow bee’ because it is the size of a small bird!”

There are two closely related Asian giant hornet species that are nearly identical in size and behaviours. Together, they are the largest hornets in the world, with the Vespa mandarinia species growing up to nearly two inches in length. The stinger of one of these hornets is three quarters of a centimeter long and delivers seven times as much venom as a honey bee. But, Otis insists, the sensationalist nickname has more to do with how they attack European honey bee colonies than any threat they may pose to humans. 

“They arrive at the hive entrance and slaughter all the adult bees, then harvest the larvae and the pupae and the honey and take it back to their own nest,” he said. “They have huge mandibles and they literally chop the adult bees apart. They cut their heads off or cut their bodies in half. It takes just 20 to 30 of these hornets to kill a colony of European honey bees in a couple of hours.”

While this grisly scene is what typically awaits European honey bee hives, Otis notes that their Asian counterparts, the Asian hive bees, have evolved a number of defence mechanisms to help combat these voracious predators.

The most remarkable of these techniques is what he calls heat balling. When an invading hornet enters a hive, it is swarmed by a mass of bees. 

“They rush over and form a knot of bees that generate heat just like they would to stay warm in the wintertime,” Otis said. “The bees’ lethal temperature is about two degrees centigrade above the wasp’s lethal temperature, so they literally go one degree above the wasp’s lethal temperature and cook it to death.”

But the European honey bee that we have here in Canada has not developed this type of defence, so if giant Asian hornets were to arrive here, honey bee populations would be at risk. He noted that Japanese beekeepers who manage European honey bees fit their hives with hornet traps that protect their bees.

Although giant Asian hornets were collected last year in Nanaimo and White Rock, B.C., and nearby in Washington state, Otis notes it is still unclear if and when they could establish a foothold in North America. 

He believes we’re still a couple years away from seeing how that might play out. 

“People want to know when’s it going to get here. That’s like asking, ‘When are you going to win the lottery?’ It could be tomorrow, it could be never,” he said. “I don’t know, I can’t answer that.”

In the meantime, it’s still not clear if they could survive our climate.

“They’re probably not going to colonize in super cold areas,” he said. “They’ll likely go north and south along the Pacific coast because the climate’s moderate, but I don’t think they’ll get over the Rockies on their own.”

Even if they did get help by wintering queens stowing away in a shipment of lumber, for example, it’s doubtful the hornets would be able to endure the cold winters east of the Rockies. In Ontario although the lake effect in areas such as Toronto and Hamilton may allow them to survive the winter, Otis is still not certain they could survive there.

People everywhere seem to be getting swept up in murder hornet mania, but Otis is quick to point out that, even if they did land here again, the average person is not at risk. 

“You’re more likely to be stung by a bald-faced hornet while out walking around,” he said. “In all my time in Vietnam, I’ve never heard of anybody who had been stung by a giant Asian hornet.”

The risk to humans is low, but there is still a danger. The Asian giant hornet nests in a cavity in the ground so it’s possible that someone could step on a nest and get attacked. If they got disoriented and couldn’t get away from the area quickly and got stung multiple times, Otis cautions that this could be fatal. 

He is speaking from experience. While conducting his research on bees and hornets in Vietnam, he was stung by the closely related species Vespa soror. 

“It was the worst sting I have ever experienced in my life,” Otis said. “It throbbed for two days. I could barely sleep the first night, despite having taken eight Tylenols, which I don’t think you’re supposed to do, but it was that intense.”

Although we’re not likely going to have to contend with the Asian hornets any time soon, Otis said the average person can play an important role in monitoring the situation as it unfolds. 

“Should anybody see any wasp out of the ordinary that they aren’t familiar with, they should report it,” he urged. “They should take a photo with their cellphone, put a jar over it and catch it, then contact the Ontario Ministry of Agriculture or the Guelph Insect Collection.”

Otis believes that citizen-scientists will be very helpful in tracking the spread of these hornets. 

“If they do show up and are spotted in eastern North America it’s likely to be because somebody took a photo,” he said. “It’s probably not going to be some trained professional who just happens to be in the right spot at the right time.”

Mike Commito is the Director of Applied Research & Innovation at Cambrian College. You can find all of Dr. Mike’s Q&A’s in the Discover series. Follow him on Twitter @mikecommito.