Keywords: mandarinia
Description: Vespa mandarinia is found in eastern and southeastern parts of Asia, north of the tropics. It is most common in Japan, where it has been well studied. (Abe, et al. 1982 ; Matsuura and Sakagami, 1973

Vespa mandarinia is found in eastern and southeastern parts of Asia, north of the tropics. It is most common in Japan, where it has been well studied. (Abe, et al. 1982 ; Matsuura and Sakagami, 1973 )

Vespa mandarinia tends to live in low mountains and/or forested areas. It is notably absent in plains and at higher elevations. The species creates subterranean nests by digging, coopting cavities that were dug by small rodents, or finding suitable spaces near rotted pine roots. The depth of their nests ranges between 6 and 60 cm. (Matsuura and Sakagami, 1973 ; Yamane, 1976 )

The Asian giant hornet is so named because it is the world’s largest hornet. A queen’s body length can exceed 5 cm, with a wingspan that can exceed 7.6 cm. Males and the female workers are considerably smaller than the queens (3.5 to 3.9 cm in body length). Queens and workers differ only in size. Both queens and workers have reproductive anatomy, although workers do not reproduce. Males of this species are morphologically similar to females, but as in all hymenopterans. males lack the stinger that is evolved from the ovipositor. Coloration is the same between sexes. Vespa mandarinia has a broad head that is a light shade of orange. Its antennae are typically a medium or dark shade of brown, with yellow-orange scapes. It has a set of compound eyes that range from dark brown to black. It also has three simple eyes that are similar in color to that of the compound eye. The Asian giant hornet can be distinguished from other species by the presence of a deeply incised clypeus and a rather large genae. The mandible is relatively large and is a deep orange hue, with a black tooth that can be used for burrowing.

The thorax region has a few distinguishing features. The thorax is dark brown, with a distinctly large scutellum that has a noticeable impressed medial line. Its two sets of wings are typically grey and extend far from the body. Its forelegs are brighter with dark tarsi, while the mid- and hind legs are dark brown throughout.

The abdomen (gaster) contains bands of dark brown and black, which alternate with bands that are a similar orange-yellow hue as the head. The sixth segment is entirely yellow. The stinger region can reach up to 6 mm and the associated toxin is considerably venomous. (Elzinga, 1981 ; Matsuura and Sakagami, 1973 ; Shreeves and Field, 2008 )

    Other Physical Features
  • venomous
    Sexual Dimorphism
  • female larger
  • Range length 3.5 to 5.5 cm 1.38 to 2.17 in
  • Range wingspan 3.5 to 7.6 cm 1.38 to 2.99 in

The Asian giant hornet emerges from its egg as a soft, white, apodous larva. The larva has a yellow head that is covered with chitin. The body has three thoracic and ten abdominal segments that do not have constrictions between them. The larvae feed on a paste consisting of prey that was masticated by the workers or queen. The larvae eventually grow large enough to enter the pupal stage and undergo complete metamorphosis. After metamorphosis, they emerge as adults. The workers require about 40 days to grow from egg to adult. Queens and males develop later in the season, with males maturing faster than queens. (Ross and Matthews, 1991 ; Yamane, 1976 )

Mating in Vespa mandarinia takes place during the fall. In contrast to other hornets, copulation takes place at nest entrances. Sex pheromones are also used to initiate male sexual behavior. Once a queen exits the nest, a male will seize her in mid-air, causing both of them to fall to the ground. Copulation continues for 8 to 45 seconds. Following copulation, the queen finds a place to overwinter. (Richards, 1971 ; Ross and Matthews, 1991 ; Wilson, 2005 )

After overwintering, a fertilized queen starts her colony in the spring. Once the queen has established a rudimentary nest, she produces an initial clutch of up to 40 eggs, which becomes the first generation of workers. Toward the end of summer, the queen produces thousands of additional eggs. Fertilized eggs become the queens of the next season, and unfertilized eggs become the males of the next season. The new queens and males are cared for by the workers, whereas the first generation of workers were cared for by the queen.

Vespa mandarinia has a eusocial mating system. This type of mating system involves an advanced level of colonial existence. Cooperative care for the young, overlapping generations, and the existence of reproductive and non-reproductive classes are hallmarks of eusociality, all of which are exhibited by V. mandarinia. Cooperative care for the young is observed primarily in the workers that help raise the larvae, although the queen raises the initial workers. Overlapping generations occur during the autumn, when new queens and males begin to mate while the original colony-founding queen is still alive. Vespa mandarinia colonies include diploid queens (reproductive females), workers (non-reproductive females), and haploid reproductive males. (Matsuura and Sakagami, 1973 ; Ross and Matthews, 1991 ; Takahashi, 2004 ; Yamane, 1976 )

Vespa mandarinia exhibits a great deal of parental investment. This hornet species builds nests underground, in tree hollows, or in urban buildings, which workers aggressively defend. The young are fed by adults that have chewed their prey, typically bees, into a fine paste. This paste is then regurgitated and fed to the young. The paste is highly nutritious for the growing larvae. (Lee, 2010 ; Matsuura and Sakagami, 1973 ; Ross and Matthews, 1991 ; Shreeves and Field, 2008 )

Workers live from spring until winter. Males typically die shortly after mating in the fall. Queens live for up to one year; they build colonies in the spring after their mating season, while the current adult queens die in the winter. (Matsuura and Sakagami, 1973 )

Vespa mandarinia is a eusocial species; thus, its social structure involves a complex colonial existence, which includes cooperative care of the young, overlapping generations, and the existence of reproductive and non-reproductive classes.

The species builds subterranean nests in cavities that it digs itself or that have already been dug by small rodents. These nests also can be found near rotted pine roots, in tree hollows, and even in urban structures.

Vespa mandarinia is unique in that it is the only eusocial wasp species to stage group attacks against beehives and other eusocial wasp nests. These attacks do not usually take place until the end of the summer, more than halfway through a colony’s lifespan. These group attacks can be divided into three stages. The first, termed the hunting phase, involves solitary workers waiting near the entrance to a hunted hive. These workers capture prey in flight using their mandibles. The prey are bitten to death, and body parts are removed from the mesosoma. Attacking hornets return to their nest and feed the prey to their larvae. The hunting phase can continue indefinitely, and progression to the next phase depends on the distance between the V. mandarinia nest and the prey colony.

The second phase is termed the slaughter phase. This phase involves 2 to 50 V. mandarinia hornets. The attacking hornets focus on a single hive or nest that has been marked with a chemical secreted by a V. mandarinia worker. The attackers usually stay near the hive entrance and kill counter-attacking prey. The dead bodies of the prey species are ignored during the slaughter phase. Vespa mandarinia casualties are uncommon during attacks on Apis mellifera hives, but up to half of the attackers may be killed in an encounter with another Vespa species. Once engaged in this part of the attack, the attacking hornets will not stop, even if disturbed. In a particularly long slaughter phase, attacking V. mandarinia occasionally will starve to death. The length of the slaughter phase is variable and depends on both the number of attacking hornets and the intensity of the defense.

Once the defense has ceased, the occupation phase begins. Vespa mandarinia becomes territorial, and guards will threaten other animals that come near the occupied hive by audibly clicking their mandibles. Workers often will spend the night in an occupied hive instead of in their own colony’s nest.

Japanese honeybees (unlike some other bee species) have evolved a defense against the aggression exhibited by V. mandarinia. The honeybees can detect the pheromone that V. mandarinia hornets use to mark beehives for future attacks. When they detect this pheromone, the honeybees respond by increasing the number of defenders stationed at the nest entrance. More than 500 honeybees can mob an individual hornet scout, surrounding it faster than the hornet can bite and kill them. The bees form a ball around the hornet, then vibrate their wing muscles in the same way that they warm their nest in the winter. This coordinated behavior raises the temperature and the CO2 concentration to lethal levels around the trapped hornet. The hornet cannot survive, but the bees can withstand the conditions. Thus, the honeybees kill the hornet before it can report the location of the beehive to its nestmates. (Lee, 2010 ; Matsuura and Sakagami, 1973 ; Ono, et al. 1995 ; Ross and Matthews, 1991 ; Taylor, et al. 2011 )

Vespa mandarinia workers often fly 1 to 2 km from their nest. They can travel up to 8 km from their nest.

Vespa mandarinia uses visual cues for flight navigation. Communication through scent marks and pheromones is also known to occur. Workers apply secretions to the colonies of honeybees and wasps to recruit nestmates for a group attack. A “royal court” has been observed in V. mandarinia. This “royal court” is formed by workers that cluster around a queen, licking and biting her, ingesting pheromones. Sex pheromones also are used to initiate male sexual behavior. Some acoustic communication exists in this species. Hornet larvae make an audible sound by scraping their mandibles along the cell wall, and this is believed to indicate hunger. Adult hornets also click their mandibles as a warning to organisms that come too close to their nest or a nest that they have taken over. (Ross and Matthews, 1991 ; Taylor, et al. 2011 ; Toh and Okamura, 2003 )

Vespa mandarinia is a primarily insectivorous omnivore. Workers prey mainly on beetles (Coleoptera ), but they also will hunt hornworms (Manduca ), mantids (Mantodea ), and eusocial wasp and bee species.

Vespa mandarinia is the only eusocial wasp species to attack beehives and other eusocial wasp nests. Colonies of Apis mellifera. Apis cerana. and all sympatric Vespa and Vespula species are targeted by V. mandarinia for group attacks. The bee or wasp prey collected in these attacks are chewed into a ball, which is taken to the V. mandarinia nest and fed to the larvae. After a successful attack of a beehive or other nest, the pupae of the prey species are removed from their cocoons. The bodies of larvae and pupae in the occupied hive or nest are chewed into balls and fed to V. mandarinia larvae. The most mature pupae are preferred, and larvae are taken only when no pupae remain. Some of the adult victims and dead attackers also are fed to the V. mandarinia larvae. Workers will retrieve food from an occupied nest for a period of several days to two weeks. Mass attacks are only observed in the autumn, when hundreds of new hornet queens and males are being reared in the nest. These new hornets require large amounts of protein, and the necessity of feeding them may prompt V. mandarinia nestmates to attack beehives.

Vespa mandarinia frequently eats tree sap, especially in oaks ( Quercus ). Fruits with soft pericarps and high sugar levels are also eaten. Vespa mandarinia is the only Vespa species to frequently engage in extranidal trophallaxis, or feeding outside the nest via regurgitation. Adult workers cannot digest solid foods; thus, they subsist on sap and larval saliva. All solid food is fed to larvae by trophallaxis. Extranidal trophallaxis often occurs among workers at sap sources. Most often, the flow of food is unidirectional. Reciprocal trophallaxis occurs among starving workers. These individuals will tightly embrace, hanging from a branch by a single leg, or lying or rolling on the ground. They alternately beg for and receive food, and they may maintain this embrace for over ten minutes. (Abe, et al. 1995 ; Matsuura and Sakagami, 1973 ; Ono, et al. 1995 ; Ross and Matthews, 1991 ; Taylor, et al. 2011 )

Predators of Vespa mandarinia appear to be rare; however, V. mandarinia nests are attacked by conspecific colonies, and honey buzzards may prey on this hornet.

Anti-predator adaptations include aposematic clicking with their mandibles and stinging. (Lack, 1946 ; Matsuura and Sakagami, 1973 ; Schmidt, et al. 1986 )

The Asian giant hornet dominates insect tree sap communities during the day, affecting the foraging behaviors of other species. Less dominant species must either wait for V. mandarinia to leave the patch or look for a separate patch elsewhere. Vespa mandarinia occupies the highest rank in the arthropod food web within its geographic range. During the later stages of the nesting period, V. mandarinia is the most perilous natural enemy of sympatric Vespa species at the colony level. In some years, more than half of the colonies of Polistes testaceicolor. Vespa simillima. and Vespula flaviceps may be exterminated within a particular area due to V. mandarinia group attacks.

Predators of V. mandarinia may include Pernis apivorus (honey buzzard). Vespa mandarinia also is a host to Xenos moutoni. a strepsipteran endoparasite. (Lack, 1946 ; Maeta, et al. 1998 ; Ross and Matthews, 1991 ; Yoshimoto, 2009 )

A compound derived from Vespa mandarinia larval saliva (called Vespa Amino Acid Mixture) is sold as a nutritional supplement. Mice that were administered VAAM have demonstrated increased swimming endurance, along with decreased lactate and increased glucose concentrations in their blood after swimming. These results suggest that VAAM inhibits muscle catabolism during endurance exercise and could be used to improve athletic performance. However, at the time of this writing, no peer-reviewed scientific evidence exists to suggest that this effect occurs in humans. (Abe, et al. 1995 )

Vespa mandarinia can deliver a venomous sting that is harmful to humans. In Japan, V. mandarinia causes an estimated 30 to 50 deaths each year.

Vespa mandarinia also is a major pest of apiaries in Japan. Apis mellifera is the most common apicultural species, and it has not evolved defenses against V. mandarinia. Attacks on an A. mellifera hive by 20 to 30 Asian giant hornets usually will result in the deaths of 5,000 to 25,000 bees within 1 to 6 hours. Tens of thousands of A. mellifera hives are damaged each year by V. mandarinia. (Matsuura, 1988 ; Yanagawa, et al. 2007 )

Zach Barth (author), The College of New Jersey, Thomas Kearns (author), The College of New Jersey, Elizabeth Wason (author, editor), Animal Diversity Web Staff, Keith Pecor (editor), The College of New Jersey.

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