**European Hornets** (*Vespa crabro*) are the only true hornets found in North America. They are large, aggressive predators and significant generalist feeders, playing a beneficial role in controlling various pest insects (such as grasshoppers, flies, and yellowjackets). However, they are often considered pests when they build nests near human activity, and they are known to strip the bark from ornamental shrubs and trees to obtain nesting material and sap, causing girdling and aesthetic damage.
Taxonomy and Classification
The European Hornet belongs to the family Vespidae (paper wasps, yellowjackets) in the order Hymenoptera. They are **eusocial insects**, forming large colonies with an annual life cycle (queen, workers, males, reproductives). They are often mistaken for large yellowjackets, but their larger size, distinct coloration, and unique **nocturnal activity** distinguish them from other common North American wasps.
Physical Description
European Hornets are the largest wasps in North America. Workers average $3/4$ to $1$ inch long, while queens can reach $1 \frac{1}{2}$ inches. They are reddish-brown and black with prominent yellow markings on the abdomen. Their head and thorax often have a rich, reddish hue, and their abdomen is patterned with black bands on a yellow background.
The nest is an enclosed, football-shaped paper structure built from wood fiber mixed with saliva. Nests are typically constructed in dark, sheltered voids, such as hollow trees, eaves, attics, or wall voids.
Distribution and Habitat
Native to Europe, they were introduced to the eastern United States in the mid-19th century and are now established across most of the eastern and mid-Atlantic states. Their habitat is primarily wooded areas. Unlike yellowjackets, European Hornets prefer to build their nests in **cavities** above ground, such as hollow trees, abandoned beehives, or structural voids within houses or sheds.
Behavior and Life Cycle
The colony cycle is annual. A single queen emerges from hibernation in the spring and begins building a small nest and laying eggs. The first workers emerge in early summer and take over nest expansion and foraging. The colony grows throughout the summer, peaking at several hundred workers in the fall.
A key distinguishing behavior is their **nocturnal activity**; workers are often seen flying around porch lights or windows after dark, which can cause significant alarm when they enter homes. They are also attracted to sap from trees, which is why they sometimes strip bark.
Feeding and Conflict
European Hornets are predators, feeding masticated insects to their developing larvae. Adults primarily feed on sugary substances, including tree sap and ripe fruit.
- **Aggression:** They are generally less aggressive than yellowjackets when away from the nest. However, they will defend the nest aggressively if they feel threatened. Their stinger is barbed but does not prevent the hornet from stinging multiple times.
- **Tree Damage:** They frequently scrape the bark from trees and shrubs (lilac, rhododendron, birch) to obtain wood fiber for nest construction and sap for food. This activity can result in **girdling** of young trees or branches, which may lead to the death of the limb above the damaged area.
- **Nuisance:** Their large size and noisy, aggressive flight make them alarming when encountered near the home, especially at night when they bang against windows.
Management and Prevention
Control is focused on elimination only when nests are in conflict with human activity (near doorways, inside structural voids).
- **Nest Elimination:** Due to the danger posed by a large colony, control should only be performed by a professional pest control operator. Insecticide dust is applied directly into the small nest entrance after dark when all workers are inside.
- **Exclusion:** Seal all cracks and openings (especially soffits and eaves) into attics and wall voids to prevent nest establishment.
- **Tree Protection:** If bark stripping is a problem, wrapping susceptible trees with paper or plastic wrap can deter feeding and nest material collection.
Conservation and Research
European Hornets are managed primarily as nuisance and minor tree pests. Research focuses on their predatory role in the ecosystem, particularly their interaction with native pest species and the highly invasive **Asian Giant Hornet** (*Vespa mandarinia*), though European Hornets are not effective controls against the larger Asian species.