The truth about Asian hornets: how terrified should humans and honeybees actually be?

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Can a single insect reshape history? A queen hornet from the Vespa velutina species, which is believed to have stowed away in Chinese pottery, could make that claim. She was shipped to the port of Bordeaux in 2004. Having already mated with multiple males, she flew off into the sunshine of south-west France and built a nest. From that single nest, up to 500 new queens could have emerged. For a few years, her offspring quietly prospered. By the time the authorities paid attention to this predatory yellow-legged carnivore, known as the Asian hornet, it was too late. Twenty years on, France is home to an estimated 500,000 nests, while the hornet has cruised into Spain, Portugal, Switzerland, Italy, Germany, Belgium, the Netherlands – and the UK.

Ever since the first Asian hornet turned up in Tetbury, Gloucestershire, in 2016, there have been horror stories about this “killer”, a “nasty” predator that decimates much-loved honeybees and may threaten human livelihoods and health. The stories have reached fever pitch recently: “UK Asian hornet hotspots mapped as killer species invades Britain” warned the Express on Tuesday. We love a good villain, especially a “foreign” one. But is this media scaremongering? How destructive is this recent European arrival? And will it become a permanent British resident this summer?

Since establishing itself in France, the Asian hornet has found the Channel’s waters to be a barrier, but “last year was a bit of a gamechanger,” according to Ian Campbell of the British Beekeepers Association (BBKA), which represents 25,000 hobbyist beekeepers. Until last summer, there were only a handful of sightings each year after 2016 – and each time the government’s crack National Bee Unit (NBU) quickly destroyed individuals and their nests. In 2022, just one hornet was spotted and captured and one nest destroyed.

However, in 2023, 73 nests had to be destroyed. The Asian hornet established strongholds along the coast of Kent – where about 50 nests were found – but colonies were also discovered in East Sussex, Hampshire and east London, as well as farther north in Hull and even Newcastle.

This spring, Asian hornets were first spotted in Britain in March, a month earlier than usual, suggesting that some may have overwintered here for the first time. Genetic analysis of three hornet queens found this month at Four Oaks in East Sussex indicate that they were overwintered offspring of a nest that was destroyed in Rye, 25 miles south, in November last year.

Asian hornet nests can grow to the size of a watermelon by late summer. Photograph: Thomas Lenne/Alamy

The reason for the rise in numbers is simple: there is a booming population along the coasts of France and Belgium. Asian hornets are stowing away in lorries and, occasionally, holidaymakers’ cars and reaching us via ferry. Some experts also believe that, with favourable winds, a hornet could cross the Channel by itself.

The Asian hornet is smaller than the UK’s native European hornet (which has a more gingery hue), but larger than a queen wasp. It is blacker in appearance than our native hornet and wasps and sports distinctive yellow legs and an orange face. Its abdomen is mostly black, except for one thick orange band; our native hornet’s abdomen is more yellow than black.

Both hornet species are mostly carnivorous – their diet is other flying insects – but whereas the European hornet has evolved alongside existing insect populations, the Asian hornet is new to Europe. Its population explosion suggests its numbers are not being kept in check by natural predators or pathogens.

Beekeepers are particularly concerned. Asian hornets have been widely observed hovering outside beehives and picking off worker bees as they emerge. “A honeybee hive is like a supermarket for the hornets,” says Campbell.

One Asian hornet can hunt and consume up to 50 bees in a day, but their collective impact is most significant. Asian hornet nests are unusually large; they can grow to the size of a watermelon by late summer. Each can contain 3,000 hornets. A French study found that a single Asian hornet nest consumes 11.3kg of insects each summer. A typical honeybee weighs 116mg. “That’s a heck of a lot of insects in an environment where we are already worried about falls in insect populations,” says Campbell. “The impact on biodiversity could be very significant.”

‘A honeybee hive is like a supermarket for Asian hornets.’ Photograph: Biosphoto/Alamy

Apart from killing honeybees, the presence of predatory Asian hornets causes worker bees to go into “foraging paralysis”: they hide in the hive, failing to acquire enough nectar and pollen to survive winter. It is difficult to determine the precise impact of the hornets’ arrival, because so many variables shape honeybee productivity. In Portugal, beekeepers in some regions claim 50% of their hives have been lost because of Vespa velutina; French beekeepers attribute 29% of honeybee colony mortality to the hornets.

The economic impact is widespread. In continental Europe, ripening fruit in vineyards and orchards has been despoiled by Asian hornets, posing a threat to wine and fruit production. In France, some outdoor markets have had to move indoors because the hornets are attracted to the fresh fruit, fish and meat.

There are also fears for public health. Early summer nests can be built fairly low to the ground, before colonies move high into trees in late summer. Spring queens are not particularly aggressive – they have a colony to build – but if someone stumbled into a nest at ground level it could be catastrophic. When the hornets establish themselves in Britain, those who work outdoors – farmers, gardeners, railway engineers – could be vulnerable. Deaths have been reported in France after allergic reactions to multiple stings, but there is no reliable data.

Some question this narrative of fear. Chris Packham has argued in the Guardian that there are worse threats to biodiversity than these “brutal bovver buzzers”, most notably the cocktail of pesticides sprayed over British farmland, including those banned by the EU. Some scare stories have been inaccurate, instead evoking the Asian giant hornet, which is a separate species, Vespa mandarinia, the tropics-loving “murder hornet” now terrorising parts of North America. This species is unlikely to establish itself in the UK because the climate is too cold.

So, how worried should we be? Relatively few scientific studies have quantified the Asian hornet’s impact on biodiversity and insect abundance so far, but scientists are taking the convincing, albeit mostly anecdotal, evidence seriously. “Ecologically, yes, it will alter things. I don’t think it’s going to be devastating,” says Seirian Sumner, a professor of behavioural ecology at UCL. “Unless you are a honeybee farmer, you probably don’t need to worry too much. I worry on behalf of the other social wasps, because they represent a significant proportion of their diet, but I’m sure I’m alone in that.

We need to encourage people to embrace every facet of nature, no matter how scary.’ Photograph: Nature Picture Library/Alamy

“I also worry about how it’s going to affect public perceptions of wasps and hornets. We are at a time where we need to be encouraging people to embrace every facet of nature, no matter how revolting or scary, because every part of an ecosystem has a role to play. And we are the cause of all these invasive insects.”

A scientific study examining the hornet’s impact on the native buff-tailed bumblebee found that the hornets could catch the bee and start to fly off with it, but the bee would then drop to the ground, pulling the hornet down with it. “It seems that bumblebees have this evolved behaviour that is already giving them a defence and resilience,” says Sumner.

Britain’s defences against the hornet have been criticised by some, but many experts, including beekeepers and scientists, defend the efforts of the government’s NBU and the Non-Native Species Secretariat, which highlights the dangers of invasive species inadvertently brought to Britain, such as Japanese knotweed. Many Asian hornet media stories have been triggered not by a predilection for scaremongering, but by this government-led drive to encourage the public to report Asian hornet sightings so that the species can be held at bay.

The government is still committed to “eradication”, but future scenarios include “containment” and then the “new normal” – accepting that the Asian hornet is here to stay. Prof Helen Roy of the UK Centre for Ecology and Hydrology is impressed that this effort has prevented the species’ establishment for eight years. “Hopefully, the same will happen this year. Prevention is by far the most important way to address the threat of invasive species,” she says. “We are right to consider invasive species as one of the main five drivers of biodiversity loss. And social insects, such as Vespa velutina and ant species, are a particular concern. There is good evidence of the impact that they are having on native biodiversity.”

In 2022, there were 8,000 potential sightings, reported mostly via the free app Asian Hornet Watch. Last year, 20,000 potential sightings were investigated by verifiers; only about 150 of these sightings turned out to be genuine. The NBU’s 60 officers were then dispatched to destroy nests. “People still struggle with its identification – and that’s understandable, because insect ID is not straightforward – but I feel really inspired by the citizen science and people’s willingness to get involved,” says Roy. “The beekeeping community have been amazing at raising awareness as well.”

Campbell fears that this year could determine whether the government continues its eradication policy or is so overwhelmed by sightings that it has to resort to containment. “There were tensions last year when the speed and scale of responses didn’t always match the threat level,” he says. “We know the NBU is a small unit and we know this is a once-in-a-lifetime opportunity to stop the hornets establishing. Once they are established, it will be nigh on impossible to get them out.”

‘We are the cause of all these invasive insects.’ Photograph: Nicolas Reusens/Getty Images

Technology may help. Scientists at the University of Exeter have developed VespAI, an automated bait station that alerts operators to the presence of Asian hornets. The hornets can also be caught and fitted with miniature radio tags so that they can be tracked back to their nest and the whole colony can be destroyed. More low-tech, but admirably effective, are silver streamers that Jersey’s hornet hunters have developed, which they attach to hornets that they catch and release. The streamers enable the hunters to track them more easily by sight, quickly locating nests.

As with most challenges posed by invasive species, the country where biodiversity has been most blitzed by rogue introductions, New Zealand, is pioneering innovative responses. It has been plagued by the common wasp (Vespula vulgaris), which we accidentally sent them in the 20th century. The wasps’ predation of aphids has altered the ecological balance of entire forests. Researchers are seeking to develop gene drives to produce sterile male wasps. Could something similar be developed here for the Asian hornet? Scientists are cautious; there is a long history of comparable biological controls producing unintended, unwanted consequences.

The invertebrate charity Buglife argues that we must eradicate the pathways by which such harmful invasive species arrive. “The Asian hornet is a poster child for invasive species. We can’t let this be the first of many – it needs to be the last,” says David Smith, Buglife’s advocacy and social change officer. “Addressing those pathways means we are probably going to capture or prevent more species from arriving, rather than focusing solely on a handful of species.”

Although the Asian hornet appears to be mostly coming to Britain on ships, its arrival also highlights the dangers of importing goods – particularly plants – in soil. “There are some easy biosecurity steps that are being ignored,” says Smith. For instance, the EU has banned British exports of plants in soil, but Britain still accepts the importation of plants in soil, bringing unknown animal life hidden in soil straight into garden centres and nurseries. “How about we make it two-way and increase our biosecurity?” says Smith.

A government action plan for better biosecurity has been drafted for some time, but it is still awaiting consultation, let alone being introduced. “There is a lack of attention, lack of focus and a lack of bringing [animal biosecurity] up to the standards of plant health,” says Smith. “It’s not an experiment we can afford to do. We can’t let the Asian hornet be this moment in time where we go: ‘It’s here now, we’ll deal with the next one when it arrives.’ It should be a real warning that others are waiting in the wings, particularly with the climate crisis.”

This article by Patrick Barkham was first published by The Guardian on 23 May 2024. Lead Image: ‘We love a good villain, especially a “foreign” one’ … the Vespa velutina AKA the Asian hornet. Photograph: Thomas Lenne/Alamy.