Japanese Giant Hornets (Vespa mandarinia japonica)

The Japanese Giant Hornet (Vespa mandarinia japonica) is one of the most dangerous insects in the world, injuring thousands and killing tens of people in its home range every year. This hornet is a member of Family Vespidae within Order Hymenoptera and is a subspecies of the Asian Giant Hornet, Vespa mandarinia. While the Asian Giant Hornet is found in Russia, China, Japan, Taiwan, Indochina, Nepal, India, and Sri Lanka, the Japanese Giant Hornet is only found in China and Japan (California Academy of Sciences, 2017). There have been reports of the species in Europe and the United States but some say that these reports stem from a mis-identification of other hornet species.

Japanese Giant Hornets nest underground, typically around rotting roots of pine trees. Sometimes the hornets will claim a burrow that was previously inhabited by a snake or rodent. These insects are usually found at low altitudes in mountainous, forested areas of Japan, meaning that contact with humans is typically limited. However, as humans encroach further into the hornets’ habitat, encounters have become more frequent. Japanese Giant Hornets are considered common, although they have not been officially classified by the IUCN Red List.

Japanese Giant Hornet queen (right) and Vespa ducalis (left). Vespa ducalis is a smaller hornet species, which is also found in Japan.

The Japanese Giant Hornet is a primitively eusocial insect. This categorization means that while a caste system can be observed in the species (including worker, drone, and queen roles) these castes are not well differentiated from each other. These hornets also cooperate in caring for their young, which undergo holometabolous development. Because adult hornets cannot consume solid foods, they rely on the excretions of their larvae for sustenance. These excretions are called vespa amino acid mixture or VAAM and contain a large amount of energy that allow adults to fly at speeds of over 25 miles per hour (Handwerk, 2002).

A Japanese Giant Hornet Drone. Drones are very similar to their female worker counterparts, but do not have a stinger.

While Japanese Giant Hornets are caring parents, the way they obtain food for their offspring is anything but kind. Voracious predators, the hornets hunt and kill many different insect species including mantises, other hornets, and bees (Campbell, 2013).  Large crushing mandibles are used to kill prey, sometimes by decapitation. The most dramatic example of predation by this species takes place when they attack a honeybee hive. Japanese honeybees have evolved alongside the hornets and therefore know how to respond to a hornet invasion. The bees lure the hornets into the hive and surround them, beating their wings rapidly. The temperature in the hive rapidly increases to 47 degrees Celsius which roasts the hornets alive while leaving the honeybees unharmed (Backshall, 2007). European honeybees on the other hand, have no defense against the hornets; they were imported to Asia and have not had time to evolve a defense.  A single hornet can kill 40 European honeybees in a minute, ripping them apart with its large jaws (Campbell, 2013). Once most of the adult bees are dead, the hornets go after the real prize, the honeybee larvae. The defenseless larvae are taken back to the hornet nest, where they are ground into a paste and fed to the hornet offspring.

While the mandibles are the Japanese Giant Hornet’s main weapon, these insects also possess another defense, a one centimeter long stinger. This stinger, which can be used as many times as the hornet desires, pumps a powerful venom into its target. The venom contains a large amount of acetylcholine and can dissolve human tissue. Most people who succumb to the venom are allergic to it, but anyone who is stung will need medical attention. While the venom of this species is not the most lethal hornet venom, it does have the highest lethal capacity. Lethal capacity is determined by the amount of venom that one individual has combined with its lethality (Schmidt, 1986).

If one is unlucky enough to come upon a Japanese Giant Hornet nest, the best course of action is to calmly walk away. Running will only encourage the hornets to pursue and possibly feel the need to defend their nest from someone they see as suspicious. Although the Japanese Giant Hornet has a reputation for being a brutal killer, these insects are just trying to raise their young and defend their family as any other eusocial insect would.

Links

European invasion of Asian Hornets: http://www.dailymail.co.uk/news/article-2648558/Emergency-powers-tackle-invasion-killer-Asian-Hornet-blamed-six-deaths-France.html

A video of Japanese Giant Hornets attacking a beekeeper’s beehive in Japan: https://www.youtube.com/watch?v=ZdtfWh9aO20

A clip from a documentary detailing how Japanese Giant Hornets attack European honeybee hives: https://www.youtube.com/watch?v=EZ1eAM8CChc

Asian Giant Hornet attacks in China and Japan in 2013 : http://www.cnn.com/2013/10/03/world/asia/hornet-attack-china/index.html

References

Backshall, S. (2007). Steve Backshall’s Venom: Poisonous Creatures in the Natural World. New Holland Publishers Ltd.

California Academy of Sciences. (2017, November). Asian Giant Hornet (Vespa mandarinia). Retrieved from iNaturalist: https://www.inaturalist.org/taxa/322284-Vespa-mandarinia

Campbell, D. (2013, October 5). Brief Summary. Retrieved from Encyclopedia of Life: http://eol.org/data_objects/26420945

Handwerk, B. (2002, October 25). “Hornets From Hell” Offer Real-Life Fright. Retrieved from National Geographic News: https://news.nationalgeographic.com/news/2002/10/1025_021025_GiantHornets.html

Schmidt, J. O., Yamane, S., Matsuura, M., & Starr, C. K. (1986). Hornet Venoms: Lethalities and Lethal Capacities. Toxicon, 950-954.

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