Asian hornet: How to identify it and what to do at the apiary?

The Asian hornet is spreading gradually in Switzerland and is becoming an increasing concern for beekeepers. It is therefore essential to recognize it reliably, distinguish its nests, and respond appropriately when in doubt. This article provides practical guidance on how to identify the species, report a suspected case correctly, and understand which protective measures at the apiary are currently the most realistic.

If in doubt: 4 immediate steps

Observe without approaching
Take photos or film
Note the location and context
Report at frelonasiatique.ch

1. Why the Asian hornet deserves beekeepers' full attention

Fig. 1: Potential distribution of the Asian hornet in Switzerland according to the CLIMEX bioclimatic model. Red: high risk, yellow: moderate risk of spread. Source: CABI, L. Seehausen.

Objective
To understand why the Asian hornet represents a growing threat to Swiss apiaries, and why early detection by beekeepers remains a central lever today.

The Asian hornet (Vespa velutina) is no longer a distant curiosity. In Switzerland it is listed among the invasive alien species whose environmental damage is considered established. Introduced into Europe in 2004, it was detected in Switzerland as early as 2017 in the canton of Jura, then in a growing number of cantons: by 2023 it had already been reported in 14 cantons. The areas most exposed to its spread include the Plateau, the Jura Arc, and certain Alpine valleys.

For the beekeeper, the implications are direct. The Asian hornet is an active predator of the honey bee: it captures foragers in hovering flight in front of the entrance. From August onwards, pressure generally intensifies as hornet colonies reach their maximum size. Towards the end of the season, direct predation inside hives may also occur. Its impact is not confined to honey bees: wild bees, hoverflies, and other insects are also hunted.

Every nest detected and reported early in the season can help limit local pressure in the months that follow and improve regional monitoring. In practice, the first observations in an area are often made by beekeepers, naturalists, or attentive members of the public. At the apiary, the most useful response is not to try to solve everything oneself, but to apply the right reflexes at the right time: identify, document, report, and then leave the operational follow-up to the competent authorities.

That is the purpose of this article: to help beekeepers identify the Asian hornet, react correctly in case of doubt, protect the apiary with realistic measures, and avoid the most common mistakes.

2. How to identify the Asian hornet

Objective
To provide concrete identification criteria for distinguishing the Asian hornet from native species, recognising its behaviour at the apiary, and identifying its nests according to the season.

Identification is most reliable when three levels of evidence are combined: the insect's appearance, its behaviour at the apiary, and the type of nest observed. In practice, a conclusion should never be drawn from the nest alone: documenting the observation with a photograph clearly showing an individual remains essential.

2.1. Identifying the insect

In the field, the most useful approach is to compare the Asian hornet directly with the European hornet (Vespa crabro), the native species.

Feature	Asian hornet (Vespa velutina)	European hornet (Vespa crabro)

Overall impression	Body predominantly dark, dark brown-black	More yellow and reddish overall
Head	Orange face when viewed from the front	Head more reddish, face more yellow
Abdomen	Predominantly dark, with a distinct orange band	Largely yellow with brown bands
Legs	Tips distinctly yellowish	More uniformly brown
Activity outside the nest at night	Ceases at dusk	Can still fly at night

Field marker: A predominantly dark insect with an orange face, yellowish leg tips, and an abdomen less yellow than that of the European hornet warrants careful examination. No single feature is always sufficient: reasoning must be based on converging indicators.

Fig. 2: Identifying the Asian hornet. Source: www.frelonasiatique.ch (photo: Carine Vogel)

2.2. Recognising its behaviour at the apiary

At the apiary, the strongest behavioural indicator is hovering flight in front of the entrance: an insect that remains facing the entrance for several seconds before flying off or attempting to seize a forager. For the beekeeper, this is a key field marker, especially when observed repeatedly. Observations are more likely on warm, sunny days and rarer in cold or wet weather.

Period	What you observe	Monitoring frequency
March – July	Young queens, primary nests in sheltered locations	Occasional, during apiary visits
From July onwards	Individuals at watering points, on food sources, and in front of the entrance	Increasing attention
August – end of November	Hovering flight, capture of foragers in flight	At least once per week, 30 min, between 9 a.m. and 7 p.m.
November – early December	Risk of direct predation inside hives	Heightened vigilance
Confirmed presence within 2 km	Any hunting behaviour in front of hives	Increased where possible

Key signal at the apiary: Repeated hovering flight in front of the entrance strongly reinforces the suspicion.

2.3 Annual cycle of the Asian hornet

Fig. 3: Annual cycle of the Asian hornet. Source: MNHN (France). Photos: JH = J. Haxaire, MD = M. Duret, QR = Q. Rome, CV = C. Villemant.

Period	What happens
March – April	Mated young queens emerge from overwintering, depending on region and weather conditions, when temperatures reach approximately 12–15 °C. They seek a sheltered location to build a primary nest.
Spring	The queen builds the first cells, lays a few eggs, and raises the first larvae alone.
After 4–6 weeks	The first workers emerge. They take over nest maintenance and brood care, while the queen thereafter devotes herself to egg laying.
From July	In approximately 70% of cases, the colony relocates to a secondary nest, most often situated in the canopy of a tree, frequently more than 10 m above the ground.
Summer	The colony grows strongly. The secondary nest can become substantially larger than the primary nest.
Early autumn	The colony produces males and sexual females (future queens).
October – November	The mated young queens leave the nest to overwinter.
Late autumn – winter	Workers, males, and the last larvae die. Only the young queens overwinter. The nest is never reused.
May to late November, sometimes December	The flight period broadly covers this duration. The species is primarily diurnal and ceases its activity outside the nest at dusk.

2.3. Identifying a nest

Primary nest and secondary nest must be clearly distinguished: they are searched for neither at the same time nor in the same locations. In approximately 70% of cases, the colony migrates from July onwards to a secondary nest. Every nest should be reported regardless of the season: even an empty nest in winter remains useful for documenting the spread of the species.

Feature	Primary nest	Secondary nest

When	March – July	From July, then through to autumn
Where	Sheltered, often accessible location: eaves, garage, shed, window frame, sometimes a bush	Tree canopy, often >10 m; sometimes a bush or the ground
General appearance	Small, often spherical, light grey	Much larger
Visibility	Often spotted by eye or by chance	Often difficult to see in foliage; easier to spot after leaf fall
What to do	Report promptly	Report; do not approach

Fig. 4: Field rule: A nest that is often pear-shaped, hanging freely in the canopy of a tree, frequently more than 10 m above the ground, and sometimes in a bush or more rarely on the ground, is more suggestive of the Asian hornet; it often becomes substantially larger than a primary nest and remains difficult to spot in foliage, becoming more visible after leaf fall. A nest hidden in a cavity (tree trunk, wall, roof) is more suggestive of the European hornet; in spring, small nests can look very similar, so a conclusion should never be drawn from the nest alone.

2.4. Confusions to avoid

Two confusions are particularly common and important:

The European hornet: a native species, more yellow and reddish in overall appearance.
The European hornet's nest: very similar morphology, especially early in the season. Without a photographed individual, it may be impossible to distinguish the two at a distance.

Absolute rule: Never draw a conclusion from the nest alone. Always try to photograph an individual before taking action.

Fig. 5: All native species must be strictly protected! It is therefore essential not to trap them or destroy nests that are not causing a problem. Source: BAFU

3. What to do if you suspect Asian hornet presence

Objective
To turn an observation into correct conduct: observe safely, document effectively, report promptly, and understand what happens next.

When faced with a suspect insect or nest, the objective is not to manage the problem yourself, but to document the situation correctly, stay safe, and pass on the information promptly. The earlier and more usable the report, the greater the chances of an effective response.

3.1. Observing without putting yourself at risk

Do not approach a suspect nest within 5 m.
Do not vibrate the support, blow towards the nest, or make sudden movements.
Do not attempt to catch the insect by hand.
At the apiary, observe soberly: repeated presence in front of the entrance, hunting behaviour, frequenting of a watering point.

If hornets start flying towards you in an agitated manner, move away immediately without running.

Practical reflex: Observe, step back, document. Do not intervene.

3.2. Documenting the case correctly

Photo or video: minimum criterion

At least one individual clearly visible and usable for identification.
A photo that is too blurry or taken from too far away often makes identification impossible.
A smartphone is sufficient: professional equipment is not required.
Do not wait for a perfect image: an imperfect but usable photo is better than no image at all.

Information to note

Date and time
Precise location: municipality, place name, or GPS coordinates if possible
Context: nearby apiary, building, forest edge, water source, approximate height of the nest

3.3. Reporting the case

The procedure is public, free of charge, and can be completed with a smartphone. It applies equally to the observation of an insect and to the discovery of a primary nest or a secondary nest.

Official platforms

Information required: first and last name, email address, telephone number, photos, and location.

It is not necessary to confirm the identification to 100% before reporting: a plausible, correctly documented case is better than a report that comes too late.

3.4. What happens after reporting

In general, reports are processed promptly. If the case is not retained, you will be informed. If the presence of the Asian hornet is confirmed, the information is passed on to the competent actors to organise the follow-up.

What is expected of the beekeeper after confirmation:

Strengthen monitoring of the apiary in the affected area
Report any new cases
Leave the operational follow-up to the competent authorities

4. Protecting the apiary: what is supported by evidence, what is not, and what remains under evaluation

Objective
To clearly distinguish between the best-supported protective measures, those not recommended at this stage, and those still under evaluation.

Protecting an apiary against the Asian hornet is not about multiplying devices, but about choosing measures proportionate to the actual pressure. The following table summarises the current state of knowledge.

Current status	Measure	Practical message
Best supported	Strengthened monitoring of the apiary and watering points	Basic measure, to be intensified when presence is confirmed
Best supported in heavily affected areas	Meshed entrance in front of the hive entrance	Concrete option when pressure is strong and confirmed
Not recommended at this stage	Trapping around hives or mass spring trapping	No convincing efficacy demonstrated; high levels of bycatch
Under evaluation	Cages, electric harps, automated detection	Interesting approaches, but not yet a standard solution for all

4.1. The best-supported measures today

The primary protection remains strengthened monitoring. It allows earlier detection of a presence, assessment of the pressure on the apiary, and adaptation of the subsequent response.

Period	Frequency	What you observe
July	Occasional	First individuals at watering points and around the apiary
August – November	Once per week, sunny days, 9 a.m.–7 p.m., 30 min	Hovering flight in front of the entrance, capture in flight
Confirmed presence within 2 km	Increased where possible	Any hunting behaviour in front of hives

In heavily affected areas, colonies can also be protected by a meshed entrance fitted in front of the hive entrance. This is currently the material measure most clearly put forward. It can hinder capture during hovering flight, without replacing reporting of cases, nest searching, or coordination of interventions.

Practical reading: monitoring first; meshed entrance when the pressure justifies it.

4.2. Measures not recommended at this stage

Bottle traps are not a standard solution for protecting hives.

No study has convincingly shown that they reduce predation pressure on colonies.
They also catch numerous non-target species: wild bees, hoverflies, native wasps.
In some cantons, the capture of insects may require authorisation.

Traps marketed as "selective" cannot be recommended at this stage either. Their efficacy and selectivity remain insufficiently quantified.

Mass trapping of queens in spring has not, to date, demonstrated a convincing reduction in nest numbers.

The most robust conclusion therefore remains: traps are not currently a standard protective measure for apiaries.

4.3. Devices still under evaluation

Several approaches appear promising but remain in the evaluation phase rather than in common practice.

Device	Status
Cages or protective nets	Promising results, but significant practical constraints
Electric harps	Under study, but results remain to be confirmed across different contexts
Automated detection and monitoring tools	In development or testing, primarily for detection and nest location

These approaches deserve to be followed, but they do not yet constitute generalised recommendations for all apiaries.

5. Avoiding mistakes: safety, reporting, and misguided solutions

Objective
To identify the most common mistakes when dealing with the Asian hornet, and to provide the simple line of conduct that avoids them.

In case of suspicion: mistakes to avoid

Do not approach a nest within 5 m
Do not attempt to destroy a nest yourself
Do not trust "miracle solutions"
Do not delay reporting while trying to verify everything alone
Document, report, then leave the follow-up to the competent authorities ►frelonasiatique.ch

With the Asian hornet, the classic mistake is wanting to act quickly and alone. Yet the safest approach is not improvisation, but a simple sequence: identify, document, report, then leave nest searching and control to the competent authorities.

5.1. Do not intervene alone on a nest

The first mistake is to want to approach, handle, or destroy a nest yourself. In the presence of a suspect nest, stay at least 5 m away, avoid disturbing it, and report it.

Do not approach unnecessarily or attempt to act alone.
Do not shake, vibrate, or open the immediate surroundings of the nest.
Leave assessment and removal to the competent authorities.

The beekeeper's role is central to monitoring and reporting, not to the technical removal of the nest.

5.2. Do not trust miracle solutions

A great deal of inaccurate information circulates, particularly regarding control methods. An appealing method is not necessarily an effective one.

Three questions to ask before adopting a method

Has it been seriously tested?
Is it recommended by the competent authorities?
Is it authorised in Switzerland?

If the answer to any of these questions is no or unknown, it is better not to use it.

Specifically to avoid

Recipes circulating on social media or YouTube
Commercial offerings without a verifiable scientific reference
Use of fire against a nest
Use of firearms
Unauthorised chemical substances or substances used outside the prescribed framework

"Doing something" must not be confused with "doing the right thing". An ineffective, dangerous, or unauthorised method can worsen the situation rather than resolve it.

5.3. Do not delay reporting while trying to verify everything alone

Another common mistake is to wait too long — either because one wants to confirm the species with absolute certainty, or because one hopes to resolve the problem without using the platform. In practice, it is better to submit a plausible, correctly documented case than to delay reporting until it is too late.

This also applies to nests discovered late. Even in winter, an empty secondary nest is still worth reporting: it documents the regional spread and helps to prepare for the following season.

The simple line of conduct to keep in mind

Identify — dark insect, orange band, hovering flight in front of the entrance
Observe — without approaching within 5 m, without disturbing
Document — photo with a visible individual, location, date, context
Report — via ►frelonasiatique.ch
Protect the apiary — strengthened monitoring, meshed entrance if the pressure justifies it
Do not intervene on the nest — leave the follow-up to the competent authorities

For any questions, it remains useful to consult the up-to-date information provided by the official platforms and the competent actors in the beekeeping sector.

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