The expansion of the yellow-legged hornet across Europe represents one of the most rapid and well-documented biological invasions of modern times. From its accidental introduction in 2004, scientific research has meticulously tracked its progress, revealing complex patterns of natural dispersal combined with human-assisted jumps.

The hornet’s progression across Europe shows a clear radial pattern from its French epicenter, punctuated by long-distance jumps:

• 2004: First establishment in Lot-et-Garonne, France (source 1)
• 2006-2007: Spread throughout southwestern France
• 2010: Detection in Spain (Basque Country)
• 2011: First records in Portugal and Belgium
• 2012: Appearance in northern Italy
• 2014: Colonization of Germany and the Netherlands
• 2016: First sightings in the United Kingdom
• 2019-2020: Confirmed presence in Luxembourg, Switzerland, and further UK expansion
• 2022-2024: Continued northward and eastward spread, with established populations now reaching Denmark and southern Norway

The Asian hornet was first confirmed in Luxembourg in September 2020. Initial reports were few, but the species has since established a growing presence. By mid-2024, 68 observations had been recorded, and 123 nests removed, showing a steady increase and confirming that the hornet is now widespread.

The species is officially listed as an invasive alien species in Luxembourg. Nest removals have increased over recent years: from a few cases in the early years, to 28 nests in 2023, and 123 nests in 2024 (source 2).

Natural dispersal: Studies estimate an average radial expansion of 78-80 km per year under favorable conditions (source 3). New queens can disperse 30-60 km from their natal nests during autumn, establishing the foundation for continued expansion.

Human-mediated jump dispersal: Long-distance leaps occur when hibernating queens are transported in vehicles, shipping containers, or plant material. These jumps of 200-300 km have created satellite populations far ahead of the natural expansion front, significantly accelerating the overall invasion rate (source 4).

Recent sophisticated modeling using climate data predicts substantial future expansion. Under moderate climate change scenarios (RCP 4.5), suitable habitat for the hornet could expand to cover much of western and central Europe by 2050 (source 5).

Key findings from recent models include:

• High suitability: France, Iberian Peninsula, Italy, UK, Benelux, Germany.
• Moderate suitability: Southern Scandinavia, parts of Eastern Europe.
• Climate barriers: Alpine regions and northern Scandinavia remain less suitable due to temperature limitations.

The models suggest that climate change will generally increase habitat suitability in northern latitudes while potentially creating heat stress in southernmost regions during summer months (source 5, 6).

Climate compatibility: The hornet thrives in temperate climates with mean annual temperatures between 8-16°C. Warmer winters due to climate change have improved overwintering survival rates, particularly in northern regions (source 6).

Ecological niche shifts: The species has demonstrated significant niche shifts in Europe compared to its native range, exploiting new habitat types and food resources. This flexibility is a hallmark of successful invasive species (source 7).

Water availability and altitude: The species shows preference for areas with reliable water sources and is currently limited to altitudes below 1,500-1,800 meters in European mountain ranges (source 8).

Understanding these spread mechanisms is essential for effective management. 

Early detection of jump dispersal events allows for rapid response before new populations become established. 

Public reporting provides invaluable data for tracking the invasion front and modeling future risk areas.