The Asian hornet (Vespa velutina), also known as the yellow-legged hornet, is an invasive species that has rapidly spread across France and other European countries since its accidental introduction in 2004. Originally from Asia, its presence has raised increasing concerns due to its impact on local ecosystems, beekeeping, and biodiversity. This article explores the biology, behavior, ecological impact of the Asian hornet, as well as effective control methods to curb its spread.
How to Identify an Asian Hornet?
The Asian hornet (Vespa velutina) can easily be confused with other hymenopterans such as the European hornet (Vespa crabro) or certain species of wasps. However, some notable differences allow for precise identification:
- Size: The Asian hornet measures between 2.5 and 3 cm for workers and up to 3.5 cm for the queen, whereas the European hornet is slightly larger (up to 4 cm for the queen).
- Body color: The Asian hornet has a completely black thorax and a brownish-orange abdomen with a wide black band and a yellow tip. In contrast, the European hornet has a yellow abdomen with distinct black stripes.
- Legs: One of the most obvious distinguishing signs is that the Asian hornet has yellow leg tips, unlike the European hornet, which has entirely brown or reddish legs.
- Head: The head of the Asian hornet is black with an orange face, while the European hornet's head is lighter with a yellowish hue.
- Nest: Asian hornet nests are often large (up to 1 meter in diameter) and built high in trees (over 10 meters), whereas the European hornet usually nests in cavities (tree holes, attics, walls).
Unlike common wasps, which are smaller (1 to 1.5 cm), with a slimmer body and bright yellow and black colors, the Asian hornet is bulkier and darker.
If you are unsure about identification, it is recommended to take a photo and report its presence to local authorities or specialized platforms.
Biology and Life Cycle of the Asian Hornet
The life cycle of the Asian hornet follows an annual pattern with several key phases:
- Hibernation (December to February): Only fertilized queens survive the winter by entering diapause in protected shelters. They emerge in spring to establish new colonies.
- Nest Foundation (March to April): Queens begin constructing a small primary nest in sheltered areas such as hedges, bushes, or artificial structures. They lay the first eggs, which will develop into workers.
- Colony Expansion (May to July): Workers take over nest expansion and food supply. The colony may relocate to a secondary nest, often high in trees or buildings.
- Intensive Predation Period (August to October): The nest population peaks, reaching thousands of individuals. During this period, predation on honeybees and other insects is at its highest.
- Reproduction and Dispersal (October to November): New queens and males are produced. After mating, the new queens seek hibernation sites, while the rest of the colony perishes as winter sets in.
Habitat and Distribution
The most probable hypothesis is that the Asian hornet was accidentally introduced into France via the trade of Asian pottery deposited in Lot-et-Garonne. Since then, the species has rapidly spread throughout the country and other European regions. It is now present in most French departments and continues its expansion north and eastward in Europe (Belgium, the Netherlands, Germany, Switzerland…). It prefers urban, peri-urban, and rural areas, building its nests in various locations, from trees to artificial structures.
Since 2016, Vespa velutina has been listed as an invasive alien species of concern by the European Union.
Feeding Behavior and Ecological Impact
The Asian hornet is a generalist predator that primarily feeds on insects, particularly honeybees, wasps, flies, and butterflies. This intense predation places significant pressure on bee populations, affecting plant pollination and agricultural production.
Moreover, the Asian hornet threatens local biodiversity by reducing pollinator populations and disrupting ecosystems. Its presence can also lead to a decline in honey production and increase stress on bee colonies, jeopardizing their survival.
Control Methods Against the Asian Hornet
Several strategies are employed to manage Asian hornet populations:
- Nest Destruction: The most effective method is to eliminate active nests between March and November. This operation must be carried out by trained professionals equipped with specific tools, including telescopic poles that allow access to high nests. MABI has designed treatment kits with telescopic extensions to reach nests over 15 meters high, applying insecticidal powders or liquids.
- Selective Trapping in Spring: Capturing founding queens in spring can help reduce new colony formation. However, this method must be used carefully to avoid trapping non-target insect species.
- Beehive Protection: Beekeepers can protect their hives by installing protective nets or electric harps, preventing hornets from attacking bees.
- Awareness and Coordination: Effective control of the Asian hornet requires cooperation among local authorities, beekeepers, and the general public. Awareness campaigns and training are crucial for reporting nests and promoting effective and environmentally friendly control methods.
Recommended Equipment for Asian Hornet Control
To safely and effectively combat the Asian hornet, appropriate equipment is essential:
1. Personal Protective Equipment (PPE)
- Full-body anti-hornet suit: Thicker than a standard beekeeper suit, featuring reinforced mesh and leather gloves.
- High boots or protective footwear: Combined with gaiters to prevent insect intrusion.
- Protective goggles: Prevents accidental exposure to chemical sprays.
- Respiratory protection: According to the manufacturer’s recommendations of the chemical product used.
Nest Treatment and Destruction Equipment
- Telescopic pole: Allows access to high nests. A special nozzle tip can pierce the nest for internal insecticide spraying.
- Pressure sprayer: Efficiently applies insecticide inside the nest.
- Specific insecticides (powders or liquids): Designed to neutralize colonies quickly.
- Capture nets: Used in some cases to trap worker hornets and prevent their dispersal.
3. Safety Measures During Intervention
- Warning signs or barrier tape: To secure the treatment area.
- Elevated work platforms: For nests located at extreme heights.
- Equipped intervention vehicle: To transport necessary equipment safely.
Conclusion
The Asian hornet poses a serious threat to biodiversity, beekeeping, and European ecosystems. A thorough understanding of its biology and behavior is essential for developing effective management strategies. Collaboration between researchers, beekeepers, local authorities, and the public is crucial to monitor and control the spread of this invasive species while minimizing