Hornet
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| Hornet | ||||||||||||||||
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European hornet, Vespa crabro | ||||||||||||||||
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Hornets are the largest eusocial wasps, reaching up to 45 millimetres (1.8 inches) 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). See wasp and bee characteristics to help identify an insect.
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[edit] Geographical distribution
The genus Vespa comprises about 20 species, most of which are native to tropical Asia, but there is a species found across temperate Eurasia from Britain to Japan, the European hornet (V. crabro), and another, Oriental hornet (V. orientalis), that extends via southern and central Asia to the Arabian peninsula, up to northern and eastern Africa and the Mediterranean basin (including southern Italy and Sicily). Another occurs in temperate eastern Asia, Yellow hornet (V. simillima), and some tropical species also range as far north as China, Siberia, or Japan. The Asian giant hornet (V. mandarinia) is a native of temperate and tropical Asia. The European hornet V. crabro, has been accidentally introduced to North America and is present in many eastern regions.
[edit] Life cycle
In Vespa crabro, the nest is founded in spring by a fertilized female, known as the queen. She generally selects sheltered places like hollow tree trunks. She builds a first 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 it 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 her way through the silk cap. This first generation of workers, invariably females, will now gradually undertake all the tasks that were 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.
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. This occurs in late summer.
At this time the queen starts producing the first reproductive individuals. Fertilized eggs develop into females (called "gynes" by entomologists), unfertilized ones 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.
[edit] Worker tasks
The workers accomplish a variety of tasks during the colony's lifetime. These include:
- Foraging. Workers feed mainly on carbohydrate-rich fluids such as tree sap. They also hunt other insects, primarily flies but also other species including smaller wasps and bees; they have been known to attack dragonflies. After subduing the prey, the hornet may discard all nutrient-poor parts such as the wings, legs, head, and/or abdomen. This leaves only the thorax with the protein-rich flight muscles, which constitutes the main food of the larvae. On hot days, workers will bring water to the nest and deposit it on the envelope, thus cooling the interior.
- Expanding and rearranging the nest. This includes building new combs and new cells.
- Feeding the larvae. On returning back to the nest, masticated prey flesh is fed to the larvae, which have higher protein needs (for growth) than the workers, since they no longer grow. The larvae, in turn, produce a nutrient fluid, rich in amino acids, which is consumed by the adults, especially the queen.
[edit] Stings
A Hornet's sting is harmful, but the sting toxicity varies greatly by hornet species. Some deliver just a typical insect sting, while others are among the most venomous known insects[1]. Allergic reactions can occur. Depending on the severity, these may result in death.
[edit] European hornet sting
- in itself is not fatal (for those without an allergy).[1]
- multiple stings (several hundred) may be fatal due to the amount of venom (similar to wasps and bees).[citation needed]
- is similar to a wasp's.
- is less toxic than a bee sting.
[edit] Non-European hornet sting
- in itself is not fatal (for those without an allergy).[1]
- multiple stings (a nest full) can be fatal due to highly toxic species-specific additions in the venom[2].
- is more toxic than a wasp's or bee's sting
- Vespa mandarinia japonica is the most venomous known insect (per sting)[1].
[edit] All hornet stings
- are an allergen for people with an allergy to wasp venom - they can suffer anaphylactic shock - a condition which can be fatal, and must be treated immediately (within a few minutes) in hospital, or before.
- the allergy (wasp allergy) is a separate allergy to bee sting allergy.
- contains less volume of venom than a bee sting.
- are primarily for killing insect prey.
- are not evolved to sting vertebrates / mammals - in contrast with a bee sting which is used for defending the nest against vertebrates/mammals (from taking honey).
- are slightly more painful than a typical wasp's due to a large amount - 5% - of acetylcholine [3]. See Schmidt Sting Pain Index [4].
As in all stinging wasps, hornets can sting multiple times - they do not die after stinging like a worker honey bee (honey bees actually survive when stinging other insects). They can also bite and sting at the same time.
[edit] Alarm escalation
Hornets, like many social wasps, can mobilize the entire nest to sting in defense. This situation is highly dangerous and must be avoided. The hornet alarm pheromone is used to raise alarm of nest attack, and to identify prey, for example bees [5]. It is not advised to kill a hornet anywhere near a nest, as the distress signal can trigger the entire nest to attack. Remove any materials - well away from hornets - that come in contact with pheromone, either on clothes, skin or dead prey or hornet. Perfumes, and other volatile chemicals can be falsely recognized as pheromone.
[edit] Pest status
Hornets and yellowjackets prey on many insects that are considered to be pests, so are actually beneficial. They do also prey on bees, but unlike honey bees, hornet and yellowjacket colonies die out every winter.
[edit] Actions to avoid
- Disturbing a nest (including vibrations and loud noises)
- Being within a few meters of a nest
- Disturbing or killing a hornet within a few meters of a nest
- Blocking the path of a hornet
- Breathing on the nest or hornet
- Rapid air movements
- Never pour gasoline or petroleum down a nest hole. This is extremely hazardous and environmentally unsound.
[edit] Hornets and other Vespidae
While taxonomically well-defined, there may be some ambiguity 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 be darker in color - see wasp and bee characteristics.
Another major difference between yellowjackets and hornets are their food choices and aggression towards humans. In the fall, yellowjackets may be attracted to human foods and food wastes, increasing potentially aggressive contact between yellowjackets and humans. Hornets, on the other hand, tend to stick to live insects.
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.
[edit] Species
- V. aethale
- V. affinis
- V. analis
- V. auraria
- V. basalis
- V. bellicosa
- V. bicincta
- V. bicolor
- V. bilineata
- V. binhami
- V. bipustulata
- V. capitata
- V. cayana
- V. chrysoptera
- V. chrysopteraarmata
- V. communis
- V. condigna
- V. conifera
- V. consimilis
- V. consobrina
- V. cordifera
- V. crabro
- V. crabroniformis
- V. crassipes
- V. cribriformis
- V. curvipes
- V. daedalea
- V. dentata
- V. diadema
- V. distincta
- V. ducalis
- V. dybowskii
- V. erythrycephala
- V. exotica
- V. ferruginata
- V. ferruginea
- V. fervida
- V. flavitarsus
- V. florisequa
- V. fluva
- V. fulvipes
- V. fumida
- V. fusus
- V. geniculata
- V. guttata
- V. hirsutissima
- V. horticola
- V. intersecta
- V. italica
- V. ligata
- V. longicornis
- V. luctuosa
- V. macrocephala
- V. magnifica
- V. mandarinia
- V. menstrua
- V. minima
- V. minuta
- V. mocsaryana
- V. mucronata
- V. multimaculata
- V. nigra Statz
- V. nigra Geoffroy
- V. ochropygos
- V. ochrosticta
- V. ocreata
- V. ordinata
- V. orientalis
- V. pacicephala
- V. petiolata
- V. philippinensis
- V. picipes
- V. pilosella
- V. pteropoda
- V. quadripunctata
- V. quinquefasciata Muller
- V. quinquefasciata Schrank
- V. scutellata
- V. sericea
- V. sessilis
- V. sexmaculata
- V. sexpustulata
- V. simillima
- V. sinuata
- V. soror
- V. sphaerogaster
- V. taenia
- V. tahitensis
- V. tenebricosa
- V. tesserazonia
- V. trizonata
- V. tropica
- V. unicolor
- V. usta
- V. velox
- V. velutina
- V. vivax
- V. xanthoptera
[edit] 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)[1].
- Black-bellied hornet Vespa basalis
- European hornet Vespa crabro, (sometimes known as Giant Hornet, Old World Hornet, or Brown Hornet).
- Greater banded hornet Vespa tropica
- Japanese hornet Vespa xanthoptera (sometimes known as Japanese yellow hornet).
- Lesser banded hornet Vespa affinis
- Oriental hornet Vespa orientalis
- Yellow hornet Vespa simillima
- Yellow-legged hornet Vespa velutina
- Vespa luctuosa the most lethal wasp venom (per volume)[1].