European Hornet
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The European hornet (''Vespa crabro'') is the largest
eusocial Eusociality ( Greek 'good' and social) is the highest level of organization of sociality. It is defined by the following characteristics: cooperative brood care (including care of offspring from other individuals), overlapping generations wit ...
wasp A wasp is any insect of the narrow-waisted suborder Apocrita of the order Hymenoptera which is neither a bee nor an ant; this excludes the broad-waisted sawflies (Symphyta), which look somewhat like wasps, but are in a separate suborder ...
native to
Europe Europe is a continent located entirely in the Northern Hemisphere and mostly in the Eastern Hemisphere. It is bordered by the Arctic Ocean to the north, the Atlantic Ocean to the west, the Mediterranean Sea to the south, and Asia to the east ...
. It is also the only true hornet (genus ''Vespa'') found in
North America North America is a continent in the Northern Hemisphere, Northern and Western Hemisphere, Western hemispheres. North America is bordered to the north by the Arctic Ocean, to the east by the Atlantic Ocean, to the southeast by South Ameri ...
, having been introduced to the United States and Canada from Europe as early as 1840. Vespines, such as ''V. crabro'', are known for making intricate paper-like nests out of surrounding plant materials and other fibers. Unlike most other vespines, reproductive suppression involves worker policing instead of queen pheromone control, as was previously thought. This species stings in response to being stepped on or grabbed, but generally avoids conflict. It is also defensive of its nest and can be aggressive around food sources. Care should be taken when they are found in these circumstances, as they may sting without warning. European hornets are largely carnivorous and hunt large insects such as
beetle Beetles are insects that form the Taxonomic rank, order Coleoptera (), in the superorder Holometabola. Their front pair of wings are hardened into wing-cases, elytra, distinguishing them from most other insects. The Coleoptera, with about 40 ...
s,
wasp A wasp is any insect of the narrow-waisted suborder Apocrita of the order Hymenoptera which is neither a bee nor an ant; this excludes the broad-waisted sawflies (Symphyta), which look somewhat like wasps, but are in a separate suborder ...
s, large
moth Moths are a group of insects that includes all members of the order Lepidoptera that are not Butterfly, butterflies. They were previously classified as suborder Heterocera, but the group is Paraphyly, paraphyletic with respect to butterflies (s ...
s,
dragonflies A dragonfly is a flying insect belonging to the infraorder Anisoptera below the order Odonata. About 3,000 extant species of dragonflies are known. Most are tropical, with fewer species in temperate regions. Loss of wetland habitat threate ...
, and mantises. They also feed on fallen fruit and other sources of sugary food. Mutual predation between medium-sized hornets and the
Asilidae The Asilidae are the robber fly family, also called assassin flies. They are powerfully built, bristly flies with a short, stout proboscis enclosing the sharp, sucking Insect mouthparts#Hypopharynx, hypopharynx. The name "robber flies" reflects t ...
(robber flies) is often reported.


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'' (e.g.) are now considered to be geographic color forms; while a history exists of recognizing subspecies within many of the ''Vespa'' species, the most recent taxonomic revision of the genus treats all subspecific names in the genus ''Vespa'' as synonyms, effectively relegating them to no more than informal names for regional color forms.A.H. Smith-Pardo, J.M. Carpenter, L. Kimsey (2020) The diversity of hornets in the genus ''Vespa'' (Hymenoptera: Vespidae; Vespinae), their importance and interceptions in the United States. Insect Systematics and Diversity 4(3) https://doi.org/10.1093/isd/ixaa006


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. Due to this coloration and abdomen pattern, ''V. crabro'' is often mistaken for the Asian giant hornet. Typical mass size for the European Hornet is . Workers average around in length, while the larger queens can reach up to . 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. There is a cerebral
ganglion A ganglion (: ganglia) is a group of neuron cell bodies in the peripheral nervous system. In the somatic nervous system, this includes dorsal root ganglia and trigeminal ganglia among a few others. In the autonomic nervous system, there are ...
, two
thoracic The thorax (: thoraces or thoraxes) or chest is a part of the anatomy of mammals and other tetrapod animals located between the neck and the abdomen. In insects, crustaceans, and the extinct trilobites, the thorax is one of the three main ...
ganglia, and five abdominal ganglia. Only females possess a stinger, it is a modified egg laying device (ovipositor): males cannot sting. The antennae of males are slightly longer, with 13 segments compared to twelve segments in females.


Nests

Individuals 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 other available plant resources are broken up, chewed, and shaped into a nest by the workers. These pieces are not uniform in shape, but are glued together very closely. Because social wasps generally prefer to build nests in the dark, envelopes are commonly found surrounding the nests to make them dark if the colony could not locate a dark crevice in which to build. The
rove beetle The rove beetles are a family (biology), family (Staphylinidae) of beetles, primarily distinguished by their short elytra (wing covers) that typically leave more than half of their abdominal segments exposed. With over 66,000 species in thousand ...
'' Velleius dilatatus'' is
commensal Commensalism is a long-term biological interaction (symbiosis) in which members of one species gain benefits while those of the other species neither benefit nor are harmed. This is in contrast with mutualism, in which both organisms benefit f ...
with the European hornet, living much of its life in the detritus of the nest.


Construction

The nest is composed of a paper-pulp mixture created by female workers chewing up dead bark, trees, or plant matter from nearby surroundings and mixing it with their saliva. To build the actual comb, saliva is used as a cement to piece together organic and inorganic materials that are readily available to the colony. This cement not only holds together the comb, but also protects the comb from being damaged by water. It provides a protective barrier to help protect the colony from wind or other harsh weather conditions. Available resources, location, and amount of mastication affect the final nest's appearance, so much variation is seen among the nests of ''V. crabro''.


Physical and chemical composition

Minerals such as
titanium Titanium is a chemical element; it has symbol Ti and atomic number 22. Found in nature only as an oxide, it can be reduced to produce a lustrous transition metal with a silver color, low density, and high strength, resistant to corrosion in ...
,
iron Iron is a chemical element; it has symbol Fe () and atomic number 26. It is a metal that belongs to the first transition series and group 8 of the periodic table. It is, by mass, the most common element on Earth, forming much of Earth's o ...
, and zirconium are commonly found in the soil and they, too, become part of the comb walls. The average dry weight of the nest is about . Cells in the paper comb are typically long and in diameter. Analysis of the composition of nests in northern Turkey revealed oxygen, carbon, and nitrogen as the main elements, while trace amounts of
silicon Silicon is a chemical element; it has symbol Si and atomic number 14. It is a hard, brittle crystalline solid with a blue-grey metallic lustre, and is a tetravalent metalloid (sometimes considered a non-metal) and semiconductor. It is a membe ...
,
calcium Calcium is a chemical element; it has symbol Ca and atomic number 20. As an alkaline earth metal, calcium is a reactive metal that forms a dark oxide-nitride layer when exposed to air. Its physical and chemical properties are most similar to it ...
, iron, and
potassium Potassium is a chemical element; it has Symbol (chemistry), symbol K (from Neo-Latin ) and atomic number19. It is a silvery white metal that is soft enough to easily cut with a knife. Potassium metal reacts rapidly with atmospheric oxygen to ...
were found, although none of
aluminium Aluminium (or aluminum in North American English) is a chemical element; it has chemical symbol, symbol Al and atomic number 13. It has a density lower than that of other common metals, about one-third that of steel. Aluminium has ...
,
magnesium Magnesium is a chemical element; it has Symbol (chemistry), symbol Mg and atomic number 12. It is a shiny gray metal having a low density, low melting point and high chemical reactivity. Like the other alkaline earth metals (group 2 ...
, or
sodium Sodium is a chemical element; it has Symbol (chemistry), symbol Na (from Neo-Latin ) and atomic number 11. It is a soft, silvery-white, highly reactive metal. Sodium is an alkali metal, being in group 1 element, group 1 of the peri ...
, providing evidence that European hornets use the surrounding soil as a resource in building their nests. The ratio of fibrous material to actual saliva affects the nest's ability to absorb water, and thus how well its inside stays dry. In the nests studied in
Turkey Turkey, officially the Republic of Türkiye, is a country mainly located in Anatolia in West Asia, with a relatively small part called East Thrace in Southeast Europe. It borders the Black Sea to the north; Georgia (country), Georgia, Armen ...
, fiber content was 23%, with 77% hornet saliva. This combination resulted in optimal water absorption capacity.


Distribution

The European hornet ''V. crabro'' originated in Eurasia. Nests historically ranged from
Japan Japan is an island country in East Asia. Located in the Pacific Ocean off the northeast coast of the Asia, Asian mainland, it is bordered on the west by the Sea of Japan and extends from the Sea of Okhotsk in the north to the East China Sea ...
to the
United Kingdom The United Kingdom of Great Britain and Northern Ireland, commonly known as the United Kingdom (UK) or Britain, is a country in Northwestern Europe, off the coast of European mainland, the continental mainland. It comprises England, Scotlan ...
. 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 Guatemala, officially the Republic of Guatemala, is a country in Central America. It is bordered to the north and west by Mexico, to the northeast by Belize, to the east by Honduras, and to the southeast by El Salvador. It is hydrologically b ...
. The few nests in Guatemala were thought to be recent, accidental introductions, as they were the first to be documented.


Life cycle

''V. crabro'' prefers to build nests in dark places, usually hollow tree trunks. After the site has been chosen, the queen lays eggs in the combs inside the nest. The workers dispose of any eggs that are not laid by their queen; this behavior is called worker policing. Based on laboratory data, the average rate of egg-laying is 2.31 eggs per day. However, in this same nest, cell construction rate was only 1.63 cells per day. ''V. crabro'' colonies seasonally change strategies of obtaining food for both the larvae and adults. In April, when the queen normally lays her eggs, the workers actively go out and forage. Later, typically around the fall season, the foraging workers switch to scavengers. Instead of putting forth the effort to catch food sources, the workers try to take what is more easily available. For example, European hornets have been seen hovering around garbage cans and picnic areas in the fall.


Worker policing

Very few workers lay eggs in healthy ''V. crabro'' colonies. While only queens mate and produce fertilized female eggs, workers are capable of laying
haploid Ploidy () is the number of complete sets of chromosomes in a cell (biology), cell, and hence the number of possible alleles for Autosome, autosomal and Pseudoautosomal region, pseudoautosomal genes. Here ''sets of chromosomes'' refers to the num ...
male eggs. Workers are generally more closely related to male offspring of other workers than to male offspring of the queen. Workers would have reproductive benefits from laying male eggs, but do not do so. This was originally thought to be caused by
pheromone A pheromone () is a secreted or excreted chemical factor that triggers a social response in members of the same species. Pheromones are chemicals capable of acting like hormones outside the body of the secreting individual, to affect the behavio ...
control by the queen, but new evidence has shown that this is not the case. Workers enforce sterility on one another in a strategy known as worker policing. Workers either physically destroy worker-laid eggs or discriminate against those workers that attempt to lay eggs. Ensuring that only the queen reproduces is thought to be likely to benefit the organization and productivity of the colony as a whole, by reducing conflicts.


Alarm behavior

Social hymenopteran species typically communicate with each other through behaviors or pheromones. In the European hornet, a typical alarm dance is performed outside of the nest and 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, internal venom sacs. 2-Methyl-3-butene-2-ol is the main pheromone component that causes ''V. crabro'' to express this defensive behavior. Other pentenols and pentanols are contained within these venomous sacs, but their primary purpose is likely not to warn fellow hornets that danger is nearby, because these chemicals do not induce alarm behavior.


Kleptoparasitism

European hornets have been observed to steal prey from
spider Spiders (order (biology), order Araneae) are air-breathing arthropods that have eight limbs, chelicerae with fangs generally able to inject venom, and spinnerets that extrude spider silk, silk. They are the largest order of arachnids and ran ...
s, which can be classified as an example of
kleptoparasitism Kleptoparasitism (originally spelt clepto-parasitism, meaning "parasitism by theft") is a form of feeding in which one animal deliberately takes food from another. The strategy is evolutionarily stable when stealing is less costly than direct f ...
. This behavior was first documented in 2011 against a yellow garden spider, '' Argiope aurantia''. A European hornet flew into the spider’s web and appeared entangled. The hornet cut free a captured insect (possibly a eumenine wasp), wrapped in silk, from the spider’s web. The spider did not attack or interfere with ''V. crabro'' while it was stealing its prey. This behavior follows the pattern of most vespines' changing their foraging techniques from hunting to scavenging, especially once the autumn season begins. ''V. crabro ''has also been observed attacking '' Polistes nimpha'' nests.


Relationship with humans


Endangered species and legal protection

Unwarranted fear of ''V. crabro'' has often led to the destruction of nests. This has led 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 Germany, officially the Federal Republic of Germany, is a country in Central Europe. It lies between the Baltic Sea and the North Sea to the north and the Alps to the south. Its sixteen States of Germany, constituent states have a total popu ...
, where killing a European hornet or nest has been illegal since January 1, 1987, with a fine up to €50,000. However, the highest reported fine levied in Germany for killing of wasps was €45, and experts report that fines are rarely imposed.


Problems associated

European hornets hunt many species of insects to feed their larvae. While many of these insects are considered to be garden pests, European hornets also prey on
western honey bee The western honey bee or European honey bee (''Apis mellifera'') is the most common of the 7–12 species of honey bees worldwide. The genus name ''Apis'' is Latin for 'bee', and ''mellifera'' is the Latin for 'honey-bearing' or 'honey-carrying', ...
s (''Apis mellifera''). However, they do not typically pose a threat to healthy western honey bee colonies, unlike the Asian hornet or Asian giant hornet, which are invasive in some parts of the world. Some
beekeeper A beekeeper is a person who keeps honey bees, a profession known as beekeeping. The term beekeeper refers to a person who keeps honey bees in beehives, boxes, or other receptacles. The beekeeper does not control the creatures. The beekeeper ow ...
s in Europe may keep hornets and their nests in specially designed boxes hanging on trees, on the premise that the protection they provide against wax moths is worth the occasional bee they may prey upon. European hornets tend to girdle branches, which results in dead branches.


Stings: case study

Most cases of stings from ''V. crabro'' do not require medical attention, but in rare cases can be serious. A documented case requiring treatment displayed symptoms including tingling at the site of the sting, headaches, and shortness of breath. In the hospital, the victim was found to have a fast, irregular heartbeat with a
blood pressure Blood pressure (BP) is the pressure of Circulatory system, circulating blood against the walls of blood vessels. Most of this pressure results from the heart pumping blood through the circulatory system. When used without qualification, the term ...
of 111/63. A subsequent EKG demonstrated
atrial fibrillation Atrial fibrillation (AF, AFib or A-fib) is an Heart arrhythmia, abnormal heart rhythm (arrhythmia) characterized by fibrillation, rapid and irregular beating of the Atrium (heart), atrial chambers of the heart. It often begins as short periods ...
with a rapid ventricular response. ''V. crabro'' venom contains
neurotransmitter A neurotransmitter is a signaling molecule secreted by a neuron to affect another cell across a Chemical synapse, synapse. The cell receiving the signal, or target cell, may be another neuron, but could also be a gland or muscle cell. Neurotra ...
s such as
dopamine Dopamine (DA, a contraction of 3,4-dihydroxyphenethylamine) is a neuromodulatory molecule that plays several important roles in cells. It is an organic chemical of the catecholamine and phenethylamine families. It is an amine synthesized ...
,
serotonin Serotonin (), also known as 5-hydroxytryptamine (5-HT), is a monoamine neurotransmitter with a wide range of functions in both the central nervous system (CNS) and also peripheral tissues. It is involved in mood, cognition, reward, learning, ...
,
histamine Histamine is an organic nitrogenous compound involved in local immune responses communication, as well as regulating physiological functions in the gut and acting as a neurotransmitter for the brain, spinal cord, and uterus. Discovered in 19 ...
and noradrenalineneurotoxin apamin, as well as enzymes phospholipase A and hyaluronidase, and proteins melittin and
bradykinin Bradykinin (BK) (from Greek ''brady-'' 'slow' + ''-kinin'', ''kīn(eîn)'' 'to move') is a peptide that promotes inflammation. It causes arterioles to dilate (enlarge) via the release of prostacyclin, nitric oxide, and endothelium-derived hyperpo ...
. These compounds have been shown to cause episodes of
tachycardia Tachycardia, also called tachyarrhythmia, is a heart rate that exceeds the normal resting rate. In general, a resting heart rate over 100 beats per minute is accepted as tachycardia in adults. Heart rates above the resting rate may be normal ...
in smaller animals. The mechanism of the described attack is still undetermined, but the victim was possibly abnormally susceptible to vespine stings. Currently, the two most effective treatments for reactions are
electrical cardioversion Cardioversion is a medical procedure by which an abnormally fast heart rate (tachycardia) or other cardiac arrhythmia is converted to a normal rhythm using electricity or drugs. Synchronized electrical cardioversion uses a therapeutic dose of ...
or propafenone. The victim in this case study was given an oral dose of propafenone (150 mg) and his atrial fibrillation resolved.


Gallery

Vespa crabro, f, side2, denmark 2016-01-08-13.29 (24091127210).jpg, ''Vespa crabro'' face Vespa crabro-dorsal.jpeg, Female ''V. crabro'' dorsal view Vespa crabro ventral view.jpg, Male ''V. crabro'' ventral view Hornets' nest.jpg, Hornets' nest in hollow tree Hornissen 720x576.ogv, Video of European hornets on their nest European-Hornet.jpg, European hornet


See also

* Hornet stings *
Paper wasp Paper wasps are a type of Eusociality, social vespid wasps. The term is typically used to refer to members of the Vespidae, vespid subfamily Polistinae, though it often colloquially includes members of the subfamilies Vespinae (hornets and yel ...
s * Vespidae


Notes


External links


European hornet protection site
* ttps://www.youtube.com/watch?v=CBWJIoNlUQg "The European hornets and oak sap" {{Authority control Vespidae Articles containing video clips Hymenoptera of Europe Wasps described in 1758 Taxa named by Carl Linnaeus Predatory animals