| 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 Asian giant hornet (V. mandarinia). It is a large insect and adults can be more than 4 centimetres (1.6 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. [1] In Japan it is known as the Oo-Suzumebachi (オオスズメバチ（大雀蜂、大胡蜂）, literally "Giant Sparrow Bee").
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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 victims in order 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 who in return produce a fluid consumed by the workers. This fluid, known as vespa amino acid mixture (VAAM), is the only sustenance workers imbibe during their adult lives, which is remarkable considering they can fly 100 kilometres (62 mi) per day and reach up to 40 kilometres per hour (25 mph). The fluid thus enables intensive muscle activities over extended periods and is being produced artificially to increase athletic performance. In many Japanese mountain villages, the hornet is considered a delicacy when fried.[1]
In Japan, beekeepers often prefer European honey bees because they are more productive than the endemic Japanese honey bees. However, it is quite difficult to maintain a captive hive of European honey bees, as the hornets will often prey on the bees.
Once a Japanese giant hornet has located a hive of European honey bees it leaves pheromone markers around it, that within a short time attract nest mates that quickly converge on the hive. A single hornet can kill forty European honey bees in a minute and a group of 30 hornets can finish off an entire hive containing 30,000 bees in a little more than three hours. The hornets not only kill the bees, but also dismember them, leaving heads and limbs behind, to finally return to their nest with the bee thoraxes which they feed to their larvae. The hornets also gorge themselves on the bees' honey.
The Japanese honey bee, on the other hand, has a defense against attacks of this manner. When a hornet approaches the hive to release pheromones, the bee workers emerge from their hive in an angry cloud-formation with some 500 individuals. As they form a tight ball around the hornet, the ball increases in heat to 47 °C (117 °F) from their vibrating wings, forming a convection oven as the heat released by the bees' bodies is spread over the hornets. Because bees can survive higher temperatures (48 to 50 °C (118 to 122 °F)) than the hornet (44 to 46 °C (111 to 115 °F)), the latter dies.[1]
The Japanese giant hornet is large and fearsome, but it is not particularly aggressive unless it feels threatened. It has a venom which is injected from the 6.25 millimetres (0.246 in) stinger and attacks the nervous system and damages tissues of its victims.[1] Compared to other hornet venom, it is not particularly lethal by weight (having an LD50 of 4.1 mg/kg, which compares to the deadliest wasp venom by weight of Vespa luctuosa at 1.6 mg/kg). Instead, the potency of its sting derives from the relatively large amount of venom it is able to inject with each sting.[2] Being stung is extremely painful and requires hospital treatment. On average 40 people die every year of anaphylactic shock after having been stung,[1] which makes the Japanese giant hornet the most lethal animal in Japan, as bears kill about ten people and venomous snakes kill five to ten people each year.