The recent media focus on unusually large or aggressive wasps has brought public attention to the question of whether hornets pose a threat to North American and European environments. Whether a hornet is a threat depends entirely on the species and its geographic location. While many hornet species are native and coexist peacefully within their natural ranges, a small number of non-native species introduced through global trade present significant ecological and economic risks outside of Asia. These introduced species have demonstrated an ability to establish themselves and negatively impact local ecosystems.
Defining True Hornets and Invasive Species
True hornets belong exclusively to the genus Vespa, a group of large, predatory, eusocial wasps native to parts of Europe and Asia. These insects are distinct from other common species often incorrectly called hornets, such as the North American bald-faced hornet, which is actually a species of yellowjacket wasp. Hornets are characterized by their robust size and the distinct shape of their heads and thoraxes.
An invasive species is defined as an organism that is non-native to a specific environment and whose introduction causes harm to the economy, the environment, or human health. Establishment occurs when a mated female, known as a gyne, is accidentally transported across continents, often within shipping containers or cargo. This single queen can then found an entire new colony, leading to a potentially disruptive population outside of its native range.
The Primary Invasive Threats: Asian Hornets
Two species represent the most publicized and concerning invasive threats globally. The Northern Giant Hornet, Vespa mandarinia, is the world’s largest hornet, with queens sometimes exceeding 45 millimeters in length. Native to temperate and tropical regions of East Asia, this species gained notoriety in North America following its detection in late 2019 in British Columbia and Washington State. While eradication efforts in the United States were successful, achieving a declaration of eradication in December 2024, its initial presence highlighted the risk of accidental introduction.
The Asian Hornet, or Yellow-legged Hornet (Vespa velutina), is a separate and smaller species that poses an active, rapidly expanding threat across Europe. Native to Southeast Asia, it was first recorded in France around 2005, believed to have arrived via commercial pottery shipments. Since then, it has spread quickly across Western Europe, establishing populations in Spain, Portugal, Belgium, and the United Kingdom. Unlike V. mandarinia, V. velutina is considered firmly established in Europe and continues to expand its range, with recent detections also occurring in the United States, such as a sighting in Georgia.
Impact on Ecosystems and Agriculture
These invasive hornets are a major concern due to their predatory behavior toward honeybee populations, especially the European honeybee (Apis mellifera). Honeybees in newly invaded regions lack the defensive behaviors that native Asian bee species evolved to counter hornet attacks, making them highly vulnerable.
The Yellow-legged Hornet, V. velutina, specializes in “hawking,” hovering outside a beehive entrance to capture foraging workers as they return. This sustained predation creates “foraging paralysis” in the honeybee colony, causing the bees to stop leaving the hive to collect food, which ultimately leads to the colony’s collapse. The Northern Giant Hornet, V. mandarinia, engages in a more devastating “slaughter phase,” where a group of hornets systematically kills all adult bees in a hive within hours to access the bee larvae and pupae as a protein source. The destruction of managed honeybee colonies poses a significant threat to agriculture, as these bees are responsible for pollinating billions of dollars worth of crops annually.
Identification and Citizen Reporting
Accurate identification is crucial for early detection, as both invasive species can be confused with native wasps or the European Hornet (Vespa crabro). The Northern Giant Hornet is recognized by its massive size and a striking appearance featuring a large, bright orange or yellow head contrasted with a dark brown thorax and a striped abdomen. In contrast, the Yellow-legged Hornet is predominantly dark, with a velvety black or dark brown thorax and abdomen, featuring a single broad yellow-orange band on its fourth abdominal segment and distinctively yellow-tipped legs.
Citizens are advised to exercise caution and never attempt to approach or eradicate a suspected nest themselves. If an insect matching the description of an invasive hornet is sighted, safely take a photograph to document its size and markings. This visual evidence should then be immediately reported to local agricultural or entomological authorities, such as the state department of agriculture, to ensure a rapid and coordinated response to the potential threat.