Featured Creature: Asian Giant Hornet

What creature comes from Southeast Asia, is the biggest of its kind, eats animals we need, and  has been tried and convicted of murder in the court of public opinion?

Meet the Asian Giant Hornet!

Warning: This is not your warm and cuddly Featured Creature.  

It was a warm and pleasant day last summer, and some of us Bio4Climate folks were entertaining out-of-town guests at our Miyawaki Forest in Cambridge, Massachusetts.  During lunch, a biologist from central Europe expressed horror at the appearance of a “new” insect.  She described it as the largest wasp she had ever seen (the differences between wasps and hornets are primarily coloring and size).

What do you think?

Indeed, it was a new insect in the Western Hemisphere – it landed in France in 2004.  Before then, its home had been limited to Southeast Asia and Japan for 16 million years as a forest dweller that mostly lives in subterranean nests.  Those in the know suspect that it somehow hitched a ride in pottery imported from China.  Perhaps it’s a bit surprising that the hornet’s international travels took so long, given that globalization has been going on for many centuries.

Photos: Bug of the Week

In many places where this creature newly appeared, authorities put out the alarm and asked citizens to take a photo of it with their cell phones but do not touch it or disturb it in any way!  It has a quarter-inch stinger and plenty of venom for repeated attacks.  It’s rarely lethal to humans, but the sting has been described as driving a hot nail into your flesh.  “Just tell us where you saw it and we’ll send in experts to try to find its nest” – no simple task with nests that are usually underground.

As it happens, people mostly mis-identified other black-and-yellow wasps as Asian Giant Hornets so the alarm was somewhat false – but the threat was real.  And the spread could happen quickly, as it did in Belgium:

Asian hornets in Belgium: August 2018, ©Vespa-Watch
Asian hornets in Belgium: August 2020, ©Vespa-Watch
Asian hornets in Belgium: July 2022, ©Vespa-Watch

If these maps resemble our recent and devastating infectious global invasive-species explosion, Covid-19,  it’s not a coincidence.  Zoonotic diseases – illnesses that jump from nonhuman animal hosts, including insects, to humans – present in patterns that resemble the spread of hornets.  The threat of another potential pandemic, albeit non-microbial, should ring alarm bells everywhere.  

But that’s a story for another day.  The current question is, “Why are we so worried about the Asian Giant Hornet?”  True, it’s a painful sting, but is there something else?

Yes, indeed.

This hornet’s favorite food is honey bees.  The bees don’t stand a chance against these aggressive and much larger adversaries.  A small crew of invaders can decimate a nest of thousands of bees in a few hours.  Their powerful jaws quickly decapitate their victims; they proceed to chew up the body into “meatballs” and deliver the meals to their own offspring.  Hence the nickname “murder hornets,” although that is rather overly dramatic – all carnivores eat other creatures.  After all, it’s an essential job in almost all ecosystems to keep a habitat’s checks and balances are working.

Bees in the hornet’s native South Asian habitat do have a defense, at least against only one or two invaders.  A team of bees surrounds the hornet, beats their wings, and raises the temperature beyond hornet tolerance – and to victory!  

Photo: Takahashi
A defensive ball of Japanese honey bees (Apis cerana japonica) in which two Japanese hornets are engulfed, incapacitated, heated, and eventually killed. This defense is also used against the Asian giant hornet.

Unfortunately, non-Asian bees haven’t had millions of years to figure out how to smother hornets.

Since honey bees are essential pollinators for many crops in addition to producers of honey, the appearance of Asian Giant Hornets in North America in 2019 mobilized beekeepers and agriculture big time.  In 2020 officials warned that if the hornets become established, they “could decimate bee populations in the United States and establish such a deep presence that all hope for eradication could be lost.”  As with many invasive species, when they establish themselves in a new place their natural predators usually don’t come along, and that disrupts the ecosystem’s function.

In the hornet’s defense from a homo sapiens perspective, it has some redeeming qualities. It’s only fair to say that it also attacks what we would call agricultural pests, and its larval silk proteins “have a wide variety of potential applications due to their [many] morphologies, including the native fiber form, but also sponge, film, and gel.”  

Finally, given that every animal eats and gets eaten eventually,

In some Japanese mountain villages, the nests are excavated and the larvae are considered a delicacy when fried. In the central Chūbu region, these hornets are sometimes eaten as snacks or an ingredient in drinks. The grubs are often preserved in jars, pan-fried or steamed with rice to make a savory dish called hebo-gohan. The adults are fried on skewers, stinger and all, until the body becomes crunchy.

In gastronomy, there is hope!

P.S. “Vespa,” by the way, is the genus of wasps and hornets.  So the next time you’re riding your bike and you hear an ever louder buzzing behind you, be grateful when it’s a gas-guzzling scooter and not its eponymous insect.

Extra featured-creature feature, red in tooth and claw: 

By Adam Sacks

Alfred Lord Tennyson In Memoriam A. H. H., 1850:
   Who trusted God was love indeed
   And love Creation’s final law
   Tho’ Nature, red in tooth and claw
   With ravine, shriek’d against his creed