Imagine a wasp the size of a human thumb, with distinctive reddish-orange wings and a body adorned in striking brown and yellow stripes. This is the European hornet (Vespa crabro), the largest eusocial wasp native to Europe and the only true hornet (genus Vespa) found in North America, having been introduced to the United States and Canada as early as 1840. These remarkable insects are known for their intricate paper-like nests and unique behaviors that set them apart from their smaller wasp relatives.
Unlike most other vespine wasps, European hornets practice a form of reproductive suppression called worker policing, where workers actively destroy eggs laid by other workers instead of relying on queen pheromone control. While they can sting in defense if stepped on or grabbed, these European hornets generally avoid conflict and are primarily carnivorous, hunting large insects such as beetles, wasps, moths, dragonflies, and mantises. They also supplement their diet with fallen fruit and other sugary food sources.
Key Takeaways
- The European hornet is the largest eusocial wasp native to Europe, with distinctive reddish-orange wings and brown/yellow striped body.
- European hornets are the only true hornets (genus Vespa) found in North America, having been introduced from Europe as early as 1840.
- These insects build intricate paper-like nests from plant materials and fibers, and use worker policing rather than queen pheromones to suppress reproduction.
- European hornets are primarily carnivorous, hunting large insects, but also feed on fallen fruit and other sugary foods.
- While they can sting in defense, European hornets generally avoid conflict and are not considered highly aggressive.
Introduction to the European Hornet
The European hornet (Vespa crabro) is a true hornet, a member of the genus Vespa, which is characterized by eusocial species. This genus belongs to the subfamily Vespinae, whose members are known for chewing their food to feed their young, as well as using paper-like materials to construct their intricate nests. According to a recent phylogenetic study, the European hornet’s closest relative is Vespa dybowskii, and the former subspecies of V. crabro are now considered to be geographic color forms.
Classification and Taxonomy
The European hornet is a true hornet (genus Vespa), a group characterized by eusocial species. The genus is in the subfamily Vespinae, members of which are known for chewing up their food to feed it to their young, as well as chewing up paper-like materials to make their nests. According to a recent phylogenetic study, its closest relative is Vespa dybowskii. The former subspecies of V. crabro are now considered to be geographic color forms.
Physical Description
The eyes of V. crabro are deeply indented and shaped like a “C”. Its wings are reddish-orange, while the petiolate abdomen is striped with brown and yellow. It has hair on the thorax and abdomen, although the European hornet is not as hairy as most bees. Typical mass size for the European Hornet is 477.5±59.9 mg. Workers average around 25 mm (1.0 in) in length, while the larger queens can reach up to 35 mm (1.4 in). This is significantly larger than most common wasps (such as Vespula vulgaris), but smaller than the Asian giant hornet. Females are typically larger than males in both size and mass. However, male abdomens have seven segments, whereas female abdomens have six.
Native Habitat and Distribution
As the name “European hornet” implies, V. crabro originated in Eurasia. Nests historically ranged from Japan to the United Kingdom. However, Saussure reported that V. crabro was introduced to North America in the mid-19th century, where it is now well established. In 2010, they were found as far south as Guatemala, but the few nests in Guatemala were thought to be recent, accidental introductions, as they were the first to be documented.
The Intricate World of European Hornet Nests
European hornets (Vespa crabro) are renowned for their remarkable nest-building abilities. These social wasps typically construct their nests using a paper-like material made from chewed wood fibers and saliva. The nests consist of a pedicle, a central paper comb, and a protective envelope surrounding the structure, with a single entry hole on the outside.
To create their nests, the workers break down twigs, branches, and other available plant materials, carefully chewing and shaping them into the desired form. Interestingly, the nest components are not uniform in shape, but are meticulously glued together to form a cohesive and sturdy structure. Additionally, the nests often incorporate minerals such as titanium, iron, and zirconium, which are commonly found in the surrounding soil, further enhancing the nest’s durability and water-resistant properties.
The average dry weight of a European hornet nest is approximately 80.87 grams (2.853 oz), with the individual cells in the paper comb typically measuring 8–9 millimetres (0.31–0.35 in) in length and 4–5 millimetres (0.16–0.20 in) in diameter. The ratio of fibrous material to the hornets’ own saliva is a critical factor in determining the nest’s water absorption capacity, with studies conducted in Turkey revealing an optimal 23% fiber content and 77% hornet saliva, resulting in excellent water resistance and moisture control within the nest.
These intricate european hornet nests not only serve as the hornets’ primary living quarters but also play a vital role in the species’ overall ecology and survival. The careful construction and unique material composition of these nests underscore the remarkable engineering abilities and adaptations of the European hornet, a fascinating insect that continues to captivate our understanding of the natural world.
European Hornet Behaviors and Life Cycle
The European hornet, Vespa crabro, exhibits a unique and fascinating life history. These social wasps prefer to build their nests in dark, enclosed spaces, such as hollow tree trunks. After choosing a nesting site, the queen lays her eggs within the combs inside the nest. Interestingly, the workers actively dispose of any eggs that are not laid by the queen, a behavior known as worker policing. Based on laboratory data, the average egg-laying rate is 2.31 eggs per day, though the cell construction rate is slightly lower at 1.63 cells per day.
Unique Life History
The European hornet colonies also demonstrate a seasonal shift in their foraging strategies. During the spring, when the queen typically lays her eggs, the workers actively forage for food. However, as the seasons change and progress towards fall, the foraging workers transition to becoming more like scavengers, taking advantage of readily available food sources such as fallen fruit and garbage.
Worker Policing and Colony Organization
Very few workers lay eggs in healthy European hornet colonies. While only the queen mates and produces fertilized female eggs, the workers are capable of laying haploid male eggs. Interestingly, workers are generally more closely related to the male offspring of other workers than to the male offspring of the queen. To maintain the colony’s organization and productivity, the workers enforce sterility on one another through a strategy called worker policing. This involves either physically destroying worker-laid eggs or discriminating against those workers that attempt to lay eggs, ensuring that only the queen reproduces.
Alarm Behavior and Communication
Social hymenopteran species, like the European hornet, often communicate with each other through behaviors or pheromones. In the case of V. crabro, a typical alarm dance is performed outside the nest. This display consists of consistent buzzing, darting in and out of the nest, and attacking or approaching the target of the alarm pheromone. The alarm pheromone is stored in and secreted from the hornet’s internal venom sacs, with 2-Methyl-3-butene-2-ol being the main pheromone component that triggers this defensive behavior.
Kleptoparasitism and Prey Acquisition
European hornets have been observed engaging in a behavior known as kleptoparasitism, where they steal prey from spiders. This behavior was first documented in 2011, when a European hornet flew into a yellow garden spider’s web, appeared entangled, and then cut free a captured insect (possibly a eumenine wasp) from the web. The spider did not attack or interfere with the hornet during this prey-stealing incident. In addition to kleptoparasitism, European hornets are also predatory for most of the year, hunting a variety of insects, including grasshoppers, flies, and yellowjackets. They have also been known to attack honey bees, although this behavior appears to be more common in Europe than in North America.
European Hornet and Humans
The European hornet, despite its large size and intimidating appearance, is often the victim of unwarranted fear and destruction. This has led to the decline of the species, which is now considered locally threatened or even endangered in some areas. Fortunately, the European hornet benefits from legal protection in certain countries, such as Germany, where killing a European hornet or its nest has been illegal since January 1, 1987, with a fine of up to €50.
Legal Protection and Conservation Efforts
The legal protection afforded to the European hornet in some regions reflects the growing awareness of the importance of conserving this remarkable insect. As a significant predator of other insects, the European hornet plays a vital role in maintaining the balance of local ecosystems. Conservation efforts aim to educate the public about the benefits of the European hornet and the need to protect its dwindling populations from unwarranted destruction.
Potential Threats and Medical Importance
Despite their large size, European hornets can pose some threats to humans and their property. They are known to strip the bark from trees and shrubs to access the sap, which can cause damage to the plants. Additionally, European hornets use the bark fiber to construct their intricate paper nests. While their sting is only about as painful as a honey bee sting, the fact that they have smooth stingers and can sting multiple times means that individuals who are allergic to bee and wasp stings or who receive multiple stings may require immediate medical attention. For most people, however, a European hornet sting will resolve on its own within one to a few hours without complications.
Conclusion
The European hornet is a fascinating and impressive insect found in Europe, Asia, and parts of North America. Known for its large size and distinctive markings, this social wasp builds intricate paper nests, exhibits complex behaviors like worker policing and kleptoparasitism, and has an important ecological role as a predator of other insects.
While European hornets can pose some risks to humans, they are generally not aggressive unless directly threatened, and efforts are underway in some regions to protect this species from unwarranted destruction. Overall, the European hornet offers valuable insights into the natural world and the remarkable adaptations of insects.
As the article has explored, the European hornet is a captivating creature that deserves further study and conservation efforts to ensure its continued presence in the ecosystems it inhabits. Its unique behaviors and intricate nesting strategies provide a glimpse into the complex social dynamics of the insect world, and its role as a predator highlights the delicate balance of nature.
