giant hornet

Asian giant hornet

The Asian giant hornet, Vespa mandarinia, also known as the Japanese hornet and known colloquially as the yak-killer hornet, is the world's largest hornet, native to temperate and tropical Eastern Asia. Its body length is approximately 50.8 mm (2.0 in), with a wingspan of about 76 mm (3 in). Queens may reach a length of 55 mm (2.2 in). Due to its size, it is known in Japan as the .

Anatomy

The head of the hornet is orange and quite wide in comparison to other hornet species. The compound eyes and ocelli are dark brown, and the antennae are dark brown with orange scapes. The clypeus (the shield-like plate on the front of the head) is orange and coarsely punctured; the posterior side of the clypeus has narrow, rounded lobes. The mandible is large and orange with a black tooth (inner biting surface).

The thorax and propodeum (the segment which forms the posterior part of the thorax) of the Asian giant hornet has a distinctive golden tint and a large scutellum (a shield-like scale on the thorax) that has a deeply-impressed medial line; the postscutellum (the plate behind the scutellum) bulges and overhangs the propodeum. The hornet's forelegs are orange with dark brown tarsi (the distal—furthest down—part of the leg); the midlegs and hindlegs are dark brown. Wings are a dark brownish-gray. The tegulae are brown.

The gaster (the portion of the abdomen behind the thoraxabdomen connection) is dark brown with a white, powdery covering; with narrow yellow bands at the posterior margins of the tergite, the sixth segment is entirely yellow. It is similar in appearance to the established European hornet, Vespa crabro.

Geographic distribution

It can be found in Primorsky Krai, Korea, China, Taiwan (where it is called 虎頭蜂; "tiger head bee"), Indochina, Nepal, India, and Sri Lanka, but is most common in mountainous areas of Japan.

Sting

The stinger of the Asian giant hornet is about 6 mm (¼ in) in length, and injects an especially potent venom that contains, like many bee and wasp venoms, a cytolytic peptide (specifically, a mastoparan) that can damage tissue by stimulating phospholipase action, in addition to its own intrinsic phospholipase. Masato Ono, an entomologist at Tamagawa University near Tokyo, described the sensation as feeling "like a hot nail being driven into my leg.".

An allergic human stung by the giant hornet may die from an allergic reaction to the venom; but the venom contains a neurotoxin called mandaratoxin which can be lethal to people who are not allergic if the dose is sufficient. Between 20 and 40 people die each year in Japan after being stung by giant hornets.

A few interesting notes on Vespa mandarinia's venom and stinger:

  • The venom contains at least eight distinct chemicals, some of which damage tissue, some of which cause pain, and at least one which has an odor that attracts more hornets to the victim.
  • The venom contains 5% acetylcholine, a greater concentration than is present in bee or other wasp venoms. Acetylcholine stimulates the pain nerve fibers, intensifying the pain of the sting.
  • Vespa mandarinia uses its large crushing mandibles, rather than its sting, to kill prey.
  • The venom of the Asian giant hornet is more toxic than that of most other bees or wasps, giving this species one of the greatest lethal capacities per colony.
  • The enzyme in the venom is so strong that it can dissolve human tissue. On some occasions, the sting may be compared to the effects of a spider bite.
  • Like all hornets, V. mandarinia has a barbless stinger, allowing it to sting repeatedly.
  • Its sting venom will also cause more hornets to be drawn to the victim.

Sting Prevention and Precautions

  • Japanese Hornets protect their nest and will attack humans that venture within about 10 meters. They will start to swarm and then attack en masse, sometimes emitting a loud noise. It is advisable therefore to retreat immediately from groups of Japanese Hornets, and at great haste should they start to emit a rattling noise.
  • Japanese Hornets will also display similarly aggressive behavior to protect food sources such as secretions of the sap of trees (e.g. Sawtooth Oak) particularly in summer, and hives of honey bees particularly in autumn (fall), and become generally aggressive when attacking other hornet nests.
  • Some types of perfume contain pheromones, particularly 2-pentanol, that are similar to the hornet pheromones that encourage a group attack. The use of perfumes and other fragrances when in areas where Japanese Hornets are present, such as mountain paths, is strongly discouraged.
  • Black clothes are said to increase the risk of Japanese Hornet attack. White clothes may also be particularly at risk at night.
  • Single stings can also be fatal, so even in the absence of small groups of hornets, extreme precaution is advised, particularly (but not only) if one has been stung before since there is a greater risk of an extreme allergic reaction.
  • Japanese Hornets are attracted to beverages containing alcohol and glucose, so care should be taken when drinking from a can or other vessel containing such liquids that has been left unattended for long enough for a hornet to enter, especially when in mountainous regions where Japanese Hornets are common.

Sting First Aid

The sting of a Japanese Hornet is extremely painful and potentially fatal, and contains chemical pheromones that attract and encourage other hornets to attack the same victim.

  • Once stung, one should attempt to retreat quickly without undue movement that might increase the chance of multiple attacks.
  • Compression and/or the use of a vacuum device to remove venom from the wound is recommended. Do not attempt to use oral suction to remove venom, since the venom would be transmitted to the mouth.
  • Wash the wound with water or better,
  • Use liquids (such as tea or wine) containing tannin to wash the wound since tannin combats the effect of one or more of the toxins.
  • The use of creams containing antihistamines and steroids is also recommended.
  • While cooling the wound, seek medical treatment immediately.
  • Those that have been stung previously are at greater risk of anaphylactic shock. Shock is the cause of the majority of fatalities from Japanese Hornet stings.

Predation

The Asian giant hornet is a relentless hunter that preys on other large insects such as bees, other hornet species, and mantises.

The hornets often attack honey bee hives with the goal of obtaining the honey bee larvae. A single scout, sometimes two or three, will cautiously approach the nest, giving off pheromones which will lead the other hornets to the hive's location.

The hornets can devastate a colony of honey bees: a single hornet can kill as many as 40 honey bees per minute thanks to their large mandibles which can quickly strike and decapitate a bee. It takes only a few of these hornets a few hours to exterminate the population of a 30,000-member hive, leaving a trail of severed insect heads and limbs. The European honey bees Apis mellifera have small stings which do little damage to hornets that are three times their size and twenty times their weight. The honey bees make futile solo attacks without mounting a collective defense, and are easily killed individually by the hornets. Once a hive is emptied of all defending bees, the hornets feed on the honey and carry the larvae back to feed to their own larvae. The hornets can fly up to 60 miles (95 km) in a single day, at speeds up to 25 mph or 40 km/h.

Adult hornets cannot digest solid protein, so the hornets do not eat their prey, but chew them into a paste and feed them to their larvae. The larvae produce a clear liquid, vespa amino acid mixture, which the adults consume; larvae of social Vespidae produce these secretions, the exact amino acid composition varying considerably among species. The passing of nutrition to adult wasps by larvae is widespread in these wasps, and not restricted to the genus Vespa.

Native honey bees

Although a handful of Asian giant hornets can easily defeat the defenses of many individual honey bees, whose small stings cannot inflict much damage against such a large predator, the Japanese honey bee (Apis cerana japonica) possesses a collective defense against them.

When a hornet scout locates and approaches a Japanese honey bee hive it will emit specific pheromonal hunting signals. When the honey bees detect these pheromones, a hundred or so will gather near the entrance of the nest and keep it open, apparently to draw the hornet further into the hive or allow it to enter on its own. As the hornet enters the nest, a large mob of about five hundred honey bees surrounds it, completely covering it and preventing it from moving, and begin quickly vibrating their flight muscles. This has the effect of raising the temperature of the honey bee mass to 47 °C (117 °F). The honey bees can just about tolerate this temperature, but the hornet cannot survive more than 45 °C (113 °F), so it dies. Often several bees perish along with the intruder, but the death of the hornet scout prevents it from summoning reinforcements which would wipe out the colony.

Life Cycle

The hornet and the Japanese diet

In Japan's mountain villages, the larvae and pupae of hornets are valued as a delicacy. They are eaten deep fried or as a kind of hornet sashimi.

Hornet supplement manufacturers

Recently, several companies in Asia and Europe have begun to manufacture dietary supplements and energy drinks which contain synthetic versions of secretions of the larvae of Vespa mandarinia, which the adult hornets usually consume. The manufacturers of these products make claims that consuming the larval hornet secretions (marketed as "hornet juice") will enhance human endurance because of the effect it has on adult hornets' performance. Because these products are marketed as dietary supplement rather than pharmaceuticals, they do not have to support their claims. Some studies, however, have suggested that the vespa amino acid mixture itself may influence animal performance in minor ways.

One such company, VAAM, manufactures several such hornet-themed supplements. According to the product's nutritional information, these all consist mostly of common amino acids and flavorings.

Notes

External links

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