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European Hornet
A female European hornet
Conservation status
Least Concern (IUCN 3.1)
Scientific classification
Kingdom:	Animalia
Phylum:	Arthropoda
Class:	Insecta
Order:	Hymenoptera
Family:	Vespidae
Genus:	Vespa
Species:	V. crabro
Binomial name
Vespa crabro Linnaeus, 1758

Metapolybia cingulata is a social paper wasp known for having queens who exhibit usurpation behaviors and also known for having flexible behavior groups. It is also difficult to tell what a specific wasp’s role is just upon observation so usually dissections have to be performed in order to determine the sex and thus the wasp’s role in the colony.1 The regulating behavior or nest building most closely resembles that of primitive Polistes models where a queen solicits liquid from a fellow worker and then takes pulp to initiate a cell without leaving the nest. In nest building, the amount of water present in the nest as well as the activity of the builders of the nests determines the activity of the colony as a whole.3

Taxonomy

Vespa crabro is a hornet that is part of the vespidae family which is characterized by eusocial wasps. It is also part of the subfamily Vespinae which is 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 phylogentic study, it’s closest relative is Vespa dybowski. Other neighbors on the phylogeny tree include: V. orientalis L., V. soror, V. mandarina, V. ducalis, V. philippinensis, V. tropica. V. cabro is also part of the aculeata lineage which is known for having stingers modified from ovipositors (organ normally used to lay eggs).

Description

Vespa crabro dorsal view

Male Vespa crabro ventral view

The eyes are deeply indented, shaped like a C. The wings are reddish-orange, while the petiolate abdomen is brown striped with yellow. The European hornet is larger than the common wasp, but smaller than some Asian hornet species. 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. Females are typically larger than males in both size and mass. Only females are equipped with an ovipositor while the males have a regular stinger. Antennae adorn both male and female heads, but typically the males are just slightly longer.

Distribution

As the name, European hornet, implies, it used to only be found in Europe. It ranged from Japan to the United Kingdom. However, Saussure found that it was introduced to North America in the mid-nineteenth century. This explains why Davis has spotted several V. crabro parasitizing spiders in Georgia. More recently, it was discovered that they have also made their way into Central America, more specifically Guatemala. As of now, the European hornet is a common find in North America, but the few who were found in Guatemala were thought to be introduced there accidentally rather recently since this is the first documented event of spotting them in Guatemala.

Life cycle

Vespa crabro prefers to build nests in dark places, usually hollow tree trunks. After the site has been chosen, the queen will lay eggs in the combs inside the nest. The workers will dispose of any eggs that aren’t from their queen directly due to worker policing. Based on a laboratory raised nest, the egg laying rate is roughly 2.31 eggs per day. However, in this same nest, the cell making rate was only 1.63 cells per day. .

As the year progresses, the colony will change their style of obtaining food for both their larvae and themselves. In April, when the queen normally lays her eggs, the workers actively go out and forage. However, typically around the fall season a change is observed in the colony as the foraging workers now turn into scavengers. Instead of putting forth the effort to go and find food sources, the workers try to take what is more easily available. For example, European hornets have been seen to hover around garbage cans and picnic areas around this season.

Life history of Vespa crabro

Worker Policing

When V. crabro sexual behaviors were first studied, it seemed that the colony was under pheromone control by the queen because none of the workers reproduced. However, new evidence has shown that even though each of the workers has the machinery to reproduce, they will only do it after weighing the cost and benefit of them laying eggs versus the queen laying eggs. In a colony with a queen, the workers are more related to the queen’s larvae than their own. Experiments performed by Foster showed that unlike previous assumptions, the workers were actually enforcing the sterility in each other. Worker policing is the behavior exhibited by fellow workers to prevent other workers within the colony from producing males. This can be completed by either physically destroying worker-laid eggs or by discriminating against those workers who wish to reproduce..

Reproductive Suppression

While workers in Vespa crabro are fully capable of reproducing, we see little or no offspring actually produced from the workers. This suppression of reproducing is not coming from the queen herself, but rather from fellow workers. This is most probably due to the fact that by letting only the queen produce larvae, the overall organization and productivity of the colony as a whole goes up because conflicts are avoided. Workers are more related to fellow workers offspring compared to the queens offspring, but by eliminating the competition and cost of having to get rid of queen eggs, the overall productivity of the colony can increase.

Species of the order Hymenoptera typically communicate with each other through behaviors or chemical excretions. In the European hornet, a typical alarm dance is performed outside of the nest and consists of consistent buzzing, dating in and out of the nest, and attacking or approaching the source of the alarm pheremone. Vespa crabro has internal venomous sacs, some of which contain pheromones that are secreted in response to alarm. Experiments done by Veith determined that 2-methyl-3-butene-2-ol is the main component which causes V. crabro to express this alarmed and defensive behavior. Other pentenols and pentanols are also contained within these venomous sacs, but their primary purpose is to not to warn fellow hornets that there is danger nearby because these chemicals did not induce any alarmed behavior..

Nesting Behavior

They typically live in paper nests, which consist of a pedicle, a paper comb on the inside, an envelope, and a single entry hole on the outside. Materials such as twigs, branches, and any other plant source available to them is broken up, chewed, and shaped into a nest by the workers. These plant fibers, leaf paste, or twigs aren't uniform in shape, but they are glued together very closely. Social wasps in general typically prefer to build nests in the dark so envelopes are commonly found surrounding the nests to make them dark if the colony couldn’t locate a dark crevice to build in.

Relationship with humans

Endangered species and legal protection

Unwarranted fear has often led to the destruction of nests, leading to the decline of the species, which is often locally threatened or even endangered. European hornets benefit from legal protection in some countries, notably Germany, where it has been illegal to kill a European hornet or nest since 1 January 1987, with a fine of up to 50,000 Euros.

Problems associated

European hornets are carnivores and eat many species of insects. Many of these insects are considered pests in the garden, which indicates that the hornet provides a benefit to the average garden/farm. However, they are known to eradicate domestic honeybee hives, resulting in fewer honeybees for open pollination. They also tend to girdle branches, which results in dead branches.

Geographic colour forms

European hornet with prey (a honeybee)

European hornet

European hornets worldwide are found with geographic colour forms:

• Vespa crabro crabro Linnaeus, 1758
• Vespa crabro vexator Harris, 1776. A European hornet found in southern counties of England, and continental Europe. This subspecies can be distinguished from the Common European hornet as V. crabro vexator has a yellow head.
• Vespa crabro germana Christ, 1791
• Vespa crabro crabroniformis Smith, 1852
• Vespa crabro borealis Radoszkowski, 1863
• Vespa crabro oberthuri du Buysson, 1902
• Vespa crabro flavofasciata Cameron, 1903
• Vespa crabro altaica Pérez, 1910
• Vespa crabro caspica Pérez, 1910
• Vespa crabro chinensis Birula, 1925

See also

• Hornet stings

External links

• European hornet protection site
• European Hornet - Penn State Entomology Department Fact Sheet

Category:Vespidae