What Is the Asian Hornet? The Yellow-Legged Hornet in Europe

Where does the Asian hornet come from?

Vespa velutina is native to a wide area of Asia, from Afghanistan and northern India east through China and Taiwan to mainland Southeast Asia and nearby islands. Several color forms live across that range. The one that has invaded Europe is a dark form from China, often called nigrithorax, meaning “black thorax”, although it is no longer treated as a separate subspecies.

Outside Europe, the Asian hornet has also become established in South Korea and on the Japanese island of Tsushima. In August 2023 a live yellow-legged hornet was confirmed near Savannah, Georgia, the first detection of the species in the United States, and it has since been found across a growing area of coastal Georgia and neighboring South Carolina. Genetic tests suggest the American population came directly from Asia rather than from Europe.

How did the Asian hornet spread across Europe?

The invasion probably began with a single mated queen, or very few, hidden in a shipment of pottery from China that reached southwestern France around 2004. The species was first identified there in 2005, in the Lot-et-Garonne department. With no competitors specialized for its lifestyle, it spread quickly.

By the end of 2015 it was reported over most of France, and since then it has reached Luxembourg, parts of Central Europe and Ireland. Since 2016 it has been on the European Union’s list of invasive alien species of Union concern, which bans keeping, breeding, selling or releasing it anywhere in the EU.

How to tell an Asian hornet from a European hornet

The two hornets are easy to tell apart with a good look, and mistaking the native European hornet for the invader is the most common error in sighting reports.

Several harmless insects are also mistaken for Asian hornets, including large hoverflies, wood wasps and big solitary wasps. A clear photo is the best way to confirm a sighting.

How do Asian hornets hunt honey bees?

The Asian hornet catches many kinds of insects, including flies, wasps and other pollinators, but the habit that worries beekeepers is called hawking. Workers hover in the air a short distance in front of a hive, each defending its own small patch of airspace, and snatch returning forager bees in mid-air. A hornet that catches a bee flies off to a nearby branch, chews the bee’s thorax into a protein-rich ball and carries it home to feed the larvae, and another hornet quickly takes its place.

In its native range, the hornet hunts the eastern honey bee, Apis cerana, which has evolved strong defenses. Its foragers dart into the hive quickly when hornets are about, and guard bees can engulf a hornet in a tight ball and cook it with the heat of their flight muscles; see how honey bees fight giant hornets. The western honey bee kept in Europe has never faced this predator. It also forms balls, but less effectively, and its foragers do not dodge hornets as well.

Hawking hornets also frighten bees into staying at home. When foragers stop flying, a colony gathers less nectar and pollen in late summer and autumn, and it may go into winter too weak to survive. The impact varies a lot between regions and years, and beekeepers in invaded areas now treat the hornet as a major threat to apiaries.

What do Asian hornet nests look like?

A queen starts in spring with a small primary nest, often in a sheltered spot such as a shed, porch, hedge or wall. As the colony grows in early summer, many colonies move and build a much larger secondary nest, often high in a tree, where it may stay hidden by leaves until autumn.

Secondary nests are roughly egg-shaped or round, made of brown paper, and often 50 cm (20 in) or more tall, sometimes close to 1 m (3 ft). Unlike the European hornet’s nest, the entrance is usually a small hole on the side. A large colony can hold well over a thousand hornets at its autumn peak and raise hundreds of new queens before the old colony dies.

Is the Asian hornet dangerous to people?

An Asian hornet foraging on flowers or fruit is not aggressive and will ignore people who ignore it. The risk comes from nests. A colony defends its nest in numbers when it feels threatened, for example when someone trims a hedge, prunes a tree or brushes past a low nest without seeing it. Keeping at least several meters away from any hornet nest is wise.

Its sting is similar to that of the European hornet. A few deaths have been reported in France and Spain, mostly after many stings near a disturbed nest or in people with venom allergy. Anyone who has trouble breathing or swelling of the face or throat after a sting should seek emergency medical help immediately by calling 911 in the US, 112 in the EU or 999 in the UK.

How to report an Asian hornet

In areas where the hornet is new or not yet established, official reports help authorities find nests early. The best approach is to take a photo from a safe distance and report it to the national or regional authority. In Great Britain, sightings go to the Non-native Species Secretariat through the Asian Hornet Watch app or its online form. In the United States, yellow-legged hornets should be reported to the state department of agriculture. Never approach or disturb a suspected nest yourself.

The Asian hornet should not be confused with the much larger northern giant hornet, nicknamed the “murder hornet”, which was found briefly in the Pacific Northwest; see are murder hornets in the US?.