Japanese giant hornet

For the Japanese hornet, see Vespa simillima.

Japanese giant hornet
Scientific classification
Kingdom:	Animalia
Phylum:	Arthropoda
Class:	Insecta
Order:	Hymenoptera
Family:	Vespidae
Genus:	Vespa
Species:	Vespa mandarinia
Subspecies:	V. mandarinia japonica

The Japanese giant hornet (Vespa mandarinia japonica) is a subspecies of the world's largest hornet, the Asian giant hornet (V. mandarinia). It is a large insect, with adults frequently growing to greater than 4.5 centimetres (1.8 in) long, with a wingspan greater than 6 centimetres (2.4 in). It has a large yellow head with large eyes, and a dark brown thorax with an abdomen banded in brown and yellow. The Japanese giant hornet has three small, simple eyes on the top of the head between the two large compound eyes. As the name implies, it is endemic to the Japanese islands, where it prefers rural areas where it can find trees to nest in. In Japanese it is known as the ōsuzumebachi (おおすずめばち（大雀蜂、大胡蜂）, literally "giant sparrow bee").

Description

Japanese giant hornet

Workers forage to feed their siblings. Their diet consists of a wide range of insects, including crop pests, and for this reason the hornets are regarded as beneficial. The workers dismember the bodies of their prey to return only the most nutrient-rich body parts, such as flight muscles, to the nest. There, the workers chew the prey into a paste before feeding the larvae which in return produce a fluid consumed by the workers. This fluid is known as vespa amino acid mixture (VAAM). Synthetic VAAM is being produced artificially as a dietary supplement, with claims that it can increase athletic performance. In many Japanese mountain villages, the hornet is considered a delicacy when fried.

Bee predation

In Japan, beekeepers often prefer European honey bees because they are more productive than the endemic Japanese honey bees. However, it can be difficult to maintain a captive hive of European honey bees, as the giant hornets are devastating to the bee hives. Once a Japanese giant hornet has located a hive of European honey bees it leaves pheromone markers around it that quickly attract nest-mates to converge on the hive. An individual hornet can kill forty European honey bees a minute while a group of 30 hornets can destroy an entire hive containing 30,000 bees in less than four hours. The hornets kill and dismember the bees, returning to their nest with the bee thoraxes, which they feed to their larvae, leaving heads and limbs behind. The honey and bee larvae are also taken to feed the hornet larvae.

Unlike their European relatives, the Japanese honey bee has a defense against the hornets. When a hornet approaches the hive to release pheromones, the bee workers will retreat back to the hive, leaving an opening to allow the hornet scout to enter. The bees then emerge from their hiding places in an angry cloud formation containing some 500 individuals. They form a tight ball around the attacking hornet that acts like a convection oven with the bees vibrating their wings to generate heat via muscular exertion and then directing the air warmed around them inward to the center of the ball. This causes the interior temperature of the ball to rise to 47 °C (117 °F). Additionally, the bees' activity also increases carbon dioxide concentration inside the ball. The hornet's ability to withstand heat decreases as carbon dioxide concentrations increase so that, ultimately, the increased temperature becomes lethal.

Venom

The Japanese giant hornet is large and can be very aggressive if provoked. Its venom, which is injected by the 6.25 mm-long stinger, attacks the nervous system and damages the tissue of its victims. Tests involving mice found that the venom falls short of being the most lethal of wasp venom, having an LD₅₀ of 4.0 mg/kg. In comparison, the deadliest wasp venom (at least to lab mice) by weight belongs to Vespa luctuosa at 1.6 mg/kg. The potency of the sting is due, rather, to the relatively large amount of venom injected. Being stung is extremely painful and can require hospitalization. The warrior wasp, tarantula hawk, and bullet ant are among the very few insects with a sting more painful. Asian giant hornet stings can cause anaphylactic shock in allergic people but can still be lethal to people who are not allergic, provided the dose is sufficient. In China, where the hornet can also be found, the conventional wisdom is that people stung more than 10 times need medical help, and emergency treatment if stung more than 30 times. The stings can also cause renal failure. Thirty to forty people die in Japan every year after having been stung by the Japanese hornet.