Today Athayde Tonhasca Júnior has another text-and-photo biology lesson for us. Athayde’s narrative is indented, and you can enlarge the photos by clicking on them. The article is about the Asian giant hornet, a creature I also wrote about in Why Evolution Is True as the opening to Chapter 5 on natural selection.
Athayde:
An undesirable pilgrim
It’s Saturday morning in an English town, and Mr and Mrs Smith set out for their favourite weekend activity – visiting the local garden centre. Wandering among rows of potted plants, clothing, shoes, tools, ceramic gnomes, barbecue gear, deck furniture and myriad other items made in China, all undoubtedly uniquely crafted, Mr and Mrs Smith spot that week’s acquisition: a gorgeous plant imported from the continent at the discounted price of £4.99. The couple drive home pleased with their purchase, which will be a nice addition to their new conservatory. Mr and Mrs Smith would be less pleased, dismayed in fact, if they knew the vase holding their plant hid a menacing stowaway: a dormant Asian hornet queen (Vespa velutina).
Mr and Mrs Smith’s tale is fiction, but something along those lines happened in France in 2004: one or more Asian hornet queens sneaked into the country hidden in pottery imported from China. When the hornet’s presence was formally recognised in the following year, it was too late. The invader had already spread out, and soon made its way into other countries in continental Europe.
Plant nurseries and garden centres are potential ports of entry for invasive species © Arpingstone, Wikimedia Commons:
Queens of hornets and related species have special skills to spend the winter safely. They build a cell in the soil, rotten wood, stumps or logs lying on the ground, also in manmade structures that offer comfy spots such as holes in ceramic pots, cracks in wooden boxes, and gaps in farming equipment. The queen will form a tunnel a few centimetres long leading to the cell and plug it with earth, scrap wood or some other material. This enclosed chamber, known as a hibernaculum (plural hibernacula), from the Latin for ‘wintering residence’, will shelter the queen from the elements, predators and pathogens. The queen also prepares herself for the long fasting spell ahead. She will put a lot of weight by tucking glycogen, lipids and proteins into her trophocytes, cells that function as a storage organ. Fats make up about 10% of a worker’s dry weight, shooting up to 40% for a queen about to go into hibernation. Despite all these measures, most queens don’t survive the harshness of winter. Those few that do, secure and well-nourished, can stay dormant for a long time – 6 to 8 months, depending on the species (Matsuura & Yamane, 1984). Eventually they come out of their slumber, fly away to build their nests, and produce a first batch of workers. From then on, colonies grow rapidly.
A German wasp queen (Vespula germanica) tucked in inside a hibernaculum built in a fallen tree © MaxNikon, Wikimedia Commons:
Queens’ ability to hibernate for long periods hidden in goods transported around the world gives the Asian hornet excellent opportunities to colonise new territories. On top of that, members of the genus Vespa have tremendous dispersal capability. Adult Asian hornets can spread at a rate of 75 to 100 km/year, and gynes (females that will mate and become queens) can fly 18 km/day. Also, hornets have high reproductive rates and adapt easily to novel conditions. They are not fussy about nesting materials and location, and the ability to thermoregulate their nests increases their chances of survival.
An Asian hornet nest. The combs that house the brood are enveloped by an external wall that keeps the nest at around 30°C, even when ambient temperatures are 20° lower © Mossot, Wikimedia Commons:
Like all related species, adult Asian hornets feed on nectar but hunt prey for their young. They have a catholic diet, going after the most abundant and vulnerable insects but not letting fortuitous opportunities such as bird and mammal carcasses go to waste. One nest can consume an average of 11.3 kg of insect biomass in one season (Rome et al., 2021), and if solitary bees, bumble bees and flies are there for the taking, pollination services may be affected. But to the consternation of beekeepers, European honey bees (Apis mellifera) make up a significant portion of the Asian hornet’s menu.
An Asian hornet taking a sip of nectar © CABI Compendium:
The ability to hover allows the Asian hornet to patrol a beehive entrance, waiting for the opportunity to pounce on a bee leaving or coming home. The hornet may even invade the hive if the entrance is unguarded (Diéguez-Antón et al., 2024). Hornets may not have to kill bees to harm a colony. Their hovering in front of a beehive may cause ‘foraging paralysis’, which is the cessation or reduction of workers’ activity (Monceau et al., 2018). By killing bees or preventing them from foraging, Asian hornets weaken the hive. Queens lay fewer eggs, bee population is reduced, and susceptibility to diseases increases. With time, the colony may collapse.
Asian hornets invading a beehive © Diéguez-Antón et al., 2024:
In some places in France and other European countries, densities have reached 5 to 6 nests/km2, and up to 12 nests/km2 in urban environments. The consequences of Asian hornet arrival are not completely understood but are not likely to be trivial. In France, up to 29% of bee colonies could be lost, with a cost of up to €30.8 million to the country’s economy (Requier et al., 2023).
Asian hornet dorsal and ventral views © Didier Descouens, Muséum de Toulouse, Wikimedia Commons:
Across the English Channel, beekeepers watch these developments with justifiable apprehension. The Asian hornet, like all other Vespa species, has a remarkable invasive potential. A British incursion could be less severe than in continental Europe because of harsher weather, but nobody wants to take chances with such a highly adaptable species. Based on the French experience, the Asian hornet would stay put if it ever gets a firm foothold in the country. There have been close calls since 2016, when Asian hornets were discovered for the first time in Britain. Their nest was found and destroyed. Subsequently, there have been other 144 confirmed sightings, with 110 nests eliminated. Thanks to scientists, technicians, members of the public and a network of dedicated beekeepers monitoring Asian hornet sightings, Britain is holding the fort. But, by tweaking a well-known quote, we can say that ‘eternal vigilance is the price for keeping Britain free of the Asian hornet’.
While British beekeepers worry, their counterparts across the Atlantic may sympathise without burdening themselves with someone else’s problem. But complacency would be a mistake. In 2019, the Asian giant hornet (V. mandarinia), an even bigger headache than V. velutina, sneaked into British Columbia and Washington State. For whatever reason, this introduction seems to have fizzled out naturally. But it could happen again. And in 2023, some Asian hornets were spotted mingling about in Savannah, Georgia. One nest was found and destroyed, but others may have escaped detection: time will tell. The take-home message is that it doesn’t pay to underestimate hardy, efficient and adaptable marvels of natural selection like Vespa wasps.
Surveillance is the best defence because eradication is much more likely to succeed in the early stages of an invasion. With alien hornets, you can’t drop your guard © The War Illustrated Album de Luxe, 1916. Wikimedia Commons:
JAC: In WEIT I discuss an adaptive strategy that honeybees have evolved in Asia, but haven’t yet in other places in the world. When the first “scout” hornet invades a nest, it’s immediately surrounded by a ball of honeybees that vibrate their wings and abdoments, cooking the hornet to death by raising the temperature. The temperature is enough to kill hornets but not bees, and the scout is unable to report back to the other wasps that it found a nest.
Always love this threading of the outside-the-box elements together into an unforgettable biology vignette.
Fascinating. Thanks as usual.
Invasive species are interesting – they’re obsessed with them in “bio-secure” Australia.
Every decade I read of a new disaster there.
D.A.
NYC
Yes, fascinating, illustrated history and warning. It also reminds me of the importance of surveillance in preventing the U.S. invasion of viruses from abroad and how the elimination of USAID and other U.S. funding of surveillance efforts at jungle/civilization interfaces in Africa and Asia will at some point leave us far behind in an ability to defend the homeland.
Nice hornet. Their smaller relatives have ruined many a picnic.
Here’s our most famous hornet—the one that invaded the Pacific Northwest briefly: the Asian Giant Hornet: https://en.wikipedia.org/wiki/Asian_giant_hornet. Everyone was afraid to go outside. As of December 2024, they are considered to have been eradicated. For now.
Wonderful, as always.
Speaking of invading queens, the vigilance required to keep these hornets out of England reminded me of this famous chess quote. Writing about passed pawns (pawns unimpeded by an enemy pawn) that want to promote and become a queen (usually), Nimzovich wrote:
“The passed pawn is a criminal, that must be kept under lock and key. Milder measures, such as police surveillance, are insufficient.”
True of hornets as well.
Always a great read. We do have the European Hornet in the south here in the US, but it does not seem to be much of an issue. That is our only ‘true’ hornet here ,since the Bald-faced Hornet is actually a large-ish Yellow Jacket.
Very interesting. Thanks.