hornet

Hornet
Oriental hornet, Vespa orientalis
Scientific classification
Kingdom:	Animalia
Phylum:	Arthropoda
Class:	Insecta
Order:	Hymenoptera
Suborder:	Apocrita
Family:	Vespidae
Subfamily:	Vespinae
Genus:	Vespa Linnaeus, 1758
Species
See text

Hornets are the largest eusocial wasps; some species can reach up to 5.5 cm (2.2 in) in length. The true hornets make up the genus Vespa and are distinguished from other vespines by the width of the vertex (part of the head behind the eyes), which is proportionally larger in Vespa and by the anteriorly rounded gasters (the section of the abdomen behind the wasp waist). The best known species is the European hornet (Vespa crabro), about 2-3 cm in length, widely distributed throughout Europe, Russia, and Northeast Asia.

Life cycle

The structure of the nest

An entire nest

In Vespa crabro, the nest is founded in spring by a fertilized female known as the queen. It generally selects sheltered places like dark hollow tree trunks. It first builds a series of cells (up to 50) out of chewed tree bark. The cells are arranged in horizontal layers named combs, each cell being vertical and closed at the top. An egg is then laid in each cell. After 5–8 days, the egg hatches, and in the next two weeks, the larva undergoes its five stages. During this time, the queen feeds it a protein-rich diet of insects. Then, the larva spins a silk cap over the cell's opening and, during the next two weeks, transforms into an adult, a process called metamorphosis. Then, the adult eats its way through the silk cap. This first generation of workers, invariably females, will now gradually undertake all the tasks formerly carried out by the queen (foraging, nest building, taking care of the brood, etc.) with one exception: egg-laying, which remains exclusive to the queen.

Life history of Vespa crabro

As the colony size grows, new combs are added, and an envelope is built around the cell layers until the nest is entirely covered with the exception of an entry hole. At the peak of its population, the colony can reach a size of 700 workers, which occurs in late summer.

At this time, the queen starts producing the first reproductive individuals. Fertilized eggs develop into females (called "gynes" by entomologists), and unfertilized ones develop into males (sometimes called "drones"). Adult males do not participate in nest maintenance, foraging, or caretaking of the larvae. In early to mid autumn, they leave the nest and mate during "nuptial flights". Males die shortly after mating. The workers and queens survive at most until mid to late autumn; only the fertilized queens survive over winter.

Other temperate species (e.g. the yellow hornet, V. simillima, or the Oriental hornet, V. orientalis) have similar cycles. In the case of tropical species (e.g., V. tropica), life histories may well differ, and in species with both tropical and temperate distributions (such as the Asian giant hornet, Vespa mandarinia), it is conceivable that the cycle depends on latitude.

Distribution

Hornets are found mainly in the Northern Hemisphere, most of them in Asia. The common european hornet, also called Vespa crabro, is the better known species, widely distributed in Europe (but is never found north of the 63rd parallel), in North China and also the only species introduced to North America, Ukraine and European Russia (except in extreme northern areas). In the east, the species' distribution area stretches over the Ural Mountains to Western Siberia (found in the vicinity of Khanty-Mansiysk). Needs to be protected in some areas. The common european hornet has also been accidentally introduced to North America about the middle of 19th century, and has lived there since about the same latitudes as in Europe, however it has never been found in western North America. In Asia, the common european hornet found in southern Siberia, as well as in eastern China.

The Asian giant hornet (Vespa mandarinia) lives in semi-dry sub-tropical areas of Asia, southern Europe, also in North Africa and along the shores of the Gulf of Aden. It can be found in the Primorsky Krai region of Russia, China, Korea, Taiwan, Cambodia, Laos, Vietnam, Indochina, India, Nepal, Sri Lanka, Thailand, but is most commonly found in the mountains of Japan, where they are commonly known as the Giant Sparrow Bee. The Asian giant hornet is also widespread in southern Europe (Italy, Malta, Albania, Romania, Greece, Bulgaria, Cyprus), in North Africa (Algeria, Libya, Egypt, Sudan, Eritrea, Somalia), in the Middle East and Central Asia (Iran, Turkey, Afghanistan, Oman, Pakistan, Turkmenistan, Uzbekistan, Tajikistan). It has been also introduced to Madagascar.

Throughout tropical Asia, it is commonly found Vespa velutina that builds nests on the open branches of trees.

Stings

Hornets have stings used to kill prey and defend hives. Hornet stings are more painful to humans than typical wasp stings because hornet venom contains a large amount (5%) of acetylcholine.^[1] See Schmidt Sting Pain Index.^[2] Individual hornets can sting multiple times; unlike typical bees, hornets and wasps do not die after stinging because their stingers are not barbed and are not pulled out of their bodies.

The toxicity of hornet stings varies according to hornet species; some deliver just a typical insect sting, while others are among the most venomous known insects.^[3] Single hornet stings are not in themselves fatal, except sometimes to allergic victims.^[3] Multiple stings by non-European hornets may be fatal because of highly toxic species-specific components of their venom.^[4] The stings of the Asian giant hornet (Vespa mandarinia japonica) are the most venomous known.^[3]

People who are allergic to wasp venom are also allergic to hornet stings. Allergic reactions are commonly treated with epinephrine (adrenaline) injection using a device such as an EpiPen, with prompt followup treatment in a hospital. In severe cases, allergic individuals may go into anaphylactic shock and die unless treated promptly.^[5]

Attack pheromone

Hornets, like many social wasps, can mobilize the entire nest to sting in defense, which is highly dangerous to animals, including humans. The hornet attack pheromone is released in case of threat to the nest, and to mark prey, such as bees.^[6] Three biologically active chemicals: 2-pentanol, 3-methyl-1-butanol, and 1-methylbutyl 3-methylbutanoate, have been identified. In field tests, 2-pentanol alone triggered mild alarm and defensive behavior, but adding the other two compounds increased aggressiveness in a synergistic effect^[6].

If a hornet is killed near a nest it may release pheromone which can cause the other hornets to attack. Materials that come in contact with pheromone, such as clothes, skin, and dead prey or hornets, can also trigger an attack, as can certain food flavorings, such as banana and apple flavorings, and fragrances which contain C₅ alcohols and C₁₀ esters.^[6]

Prey

Adult hornets and their relatives (e.g., yellowjackets) feed themselves on nectar and sugar-rich plant foods. Thus, they can often be seen on the sap of oak trees, rotting sweet fruits, honey and any sugar-containing foodstuffs. Hornets frequently fly into orchards to feast on over-ripe fruit. One who heedlessly plucks a fruit, for example a pear, where a hornet is at the moment (they tend to gnaw a hole into the fruit and to be gradually immersed in its juicy meat) can be easily attacked by the disturbed insect.

However, the adults prey on various insects as well, which they kill with stings and jaws. Due to their size and the power of poison, hornets are able to kill large or dangerous insects such as honey bees, grasshoppers and locusts without difficulty or much effort. The victim is fully masticated and then fed down in the form of slurry to the larvae developing in the nest, rather than consumed by the adult hornets. Given that some of their prey are considered pests, hornets may be considered beneficial under some circumstances.

Hornets and other Vespidae

European hornet with the remnants of a honey bee

While taxonomically well-defined, there may be some confusion about the differences between hornets and other wasps of the family Vespidae, specifically the yellowjackets, which are members of the same subfamily. Yellowjackets are generally smaller than hornets and are bright yellow and black, whereas hornets may often be black and white. Wasp and bee characteristics.

Some other large wasps are sometimes referred to as hornets, most notably the bald-faced hornet (Dolichovespula maculata) found in North America. It is set apart by its black and ivory coloration. The name "hornet" is used for this and related species primarily because of their habit of making aerial nests (similar to the true hornets) rather than subterranean nests. Another example is the Australian hornet (Abispa ephippium), which is actually a species of potter wasp.

Species

Notable species

• Asian giant hornet Vespa mandarinia
  • Vespa mandarinia japonica (sometimes known as Japanese giant hornet) - the largest wasp, and the most venomous known insect (per sting).^[3]
• Asian predatory wasp Vespa velutina
• Black-bellied hornet Vespa basalis
• Black shield wasp Vespa bicolor
• European hornet Vespa crabro, (sometimes known as Old World Hornet, or Brown Hornet).
• Greater banded hornet Vespa tropica
• Japanese hornet Vespa simillima (sometimes known as Japanese yellow hornet).
• Lesser banded hornet Vespa affinis
• Oriental hornet Vespa orientalis
• Vespa luctuosa the most lethal wasp venom (per volume).^[3]

See also

Notes

External links

Look up hornet in Wiktionary, the free dictionary.

• European hornet protection site (English) (also available in French, German, Russian, Spanish and Swedish)
• Differences between Yellowjackets and HornetsPDF (218 KiB)
• Paper Wasps and Hornets
• Hornetboy's homepage
• Controlling Wasps, Hornets, and Yellowjackets
• Hornets & Yellowjackets
• Yellowjackets and Other Social Wasps
• Vespidae of the World
• yellowjackets and hornets of Florida on the UF / IFAS Featured Creatures Web site

Wikispecies has information related to: Vespa