Giant Japanese Hornet—Japanese honeybee workers
forming a defensive ball around a giant Japanese
hornet. (Mike Shanahan)
Scientific name: Vespa mandarinia japonica
Scientific classification:
Phylum: Arthropoda
Class: Insecta
Order: Hymenoptera
Family: Vespidae
What does it look like? The giant Japanese hornet is a large insect. The adult can be more than
4 cm long with a wingspan of greater than 6 cm. It has a large yellow head with large eyes, a
dark brown thorax, and an abdomen banded in brown and yellow. Three small simple eyes
on the top of the head can be easily seen between the large compound eyes.
Where does it live? This subspecies of the Asian hornet is found on the Japanese islands. They
prefer forested areas where they make their nests in tree holes.
Marauding, Hive-Raiding Hornets
Japanese beekeepers, in an attempt to increase productivity, try to keep European honeybees
in Japan as they produce more honey than the indigenous Japanese honeybees. However, the
giant Japanese hornet often thwarts this enterprise. This hornet is a formidable brute of an
insect, which is in fact one of the largest living wasps. When a hornet locates a hive of European
honeybees, it leaves a pheromone marker all around the nest, and before long, its nest mates pick
up the scent and converge on the beehive. The hornets fl y into the beehive and begin a systematic
massacre. The European honeybee is no match for the hornet as it is one-fifth the size. A single
hornet can kill 40 European honeybees in one minute, and a group of 30 hornets can kill a
whole hive, something on the order of 30,000 bees, in a little over three hours. The defenseless
residents of the hive aren’t just killed but are horribly dismembered. After one of these attacks,
the hive is littered with disembodied heads and limbs as the hornets carry the thoraxes of the
bees back to their own nest to feed their ravenous larvae. Before they leave, the hornets also
gorge themselves on the bees’ store of honey.
This amazing natural phenomenon begs the question, well what about the native Japanese
honeybees? Do they get attacked? The answer is no, and the reason is particularly neat. The
hornet will approach the hive of the Japanese honeybee and attempt to leave a pheromone marker.
The Japanese honeybees sense this and emerge from their hive in an angry cloud. The worker bees
form a tight ball, which may contain 500 individuals, around the marauding hornet. This defensive
ball, with the hornet at its center, gets hot, aided by not only the bees vibrating their wing
muscles but also by a chemical they produce. Th e hornet, unlike the bees, cannot tolerate the high
temperature, and before long, it dies and the location of the Japanese honeybees’ nest dies with it.
• Aside from its large size and fearsome appearance, the giant Japanese hornet also has
very potent venom, which is injected through a 6.25 mm stinger. The venom attacks
the nervous system and the tissues of its victim, resulting in localized tissue damage
where the flesh is actually broken down. A sting from this insect requires hospital
treatment, and on average, 40 people are killed every year after being stung by giant
hornets, due to anaphylactic shock. Typically, the hornets are not aggressive animals,
but when threatened, they will attack. An attack initially involves one individual, but
the release of alarm pheromones will quickly attract its sisters. Not only is the venom
dangerous, but the sting is also very painful. A Japanese entomologist said of the
sting: “It was like a hot nail through my leg.”
• Hornet workers continually forage to feed their siblings developing in the nest. They
will take a range of insects, including crop pests, and for this reason, they are considered
beneficial. The insects they catch are dismembered, and typically, the most
nutritious parts, such as the flight muscles, are taken back to the nest where they
are chewed into a paste before being given to a larva. The larva returns the favor by
producing a fluid that the worker eagerly drinks.
• The fluid produced by hornet larvae has aroused interest recently as it is the only
sustenance the adult worker imbibes during its life. This substance somehow makes
prodigious feats of stamina possible, as worker hornets fl y for at least 100 km a day
at speeds of up to 40 km/h. The substance produced by the hornet larvae, known as
vespa amino acid mixture (VAAM), somehow enables intense muscular activity over
extended periods, perhaps by allowing the increased metabolism of fats. A company
has started producing VAAM commercially, and it has apparently improved the performance
of many athletes.
• Not only is VAAM popular amongst the Japanese athletic community, but the fully
grown larvae of the hornet are considered something of a delicacy and are eaten in
mountain villages, either deep-fried or as hornet sashimi.
• The defensive-ball strategy of the Japanese honeybee works because the temperature
inside the ball rises to 47°C, and the lethal temperature for the giant hornet is
44°C–46°C, whereas the lethal temperature for the bee is 48°C–50°C.
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