hornet

hornet, (genus Vespa), genus of about 20 species of the wasps (order Hymenoptera), most of which are native to Eurasia. Hornets are large social insects that tend to be black or brown with yellow or yellowish markings. Due to their size, hornets have a reputation for being more dangerous than other wasp species, though they are not always more aggressive. One species, the northern giant hornet, or Asian giant hornet (V. mandarinia), which is native to Asia, is the largest known wasp species in the world. For a full description of wasps and their natural history, see wasp.

Taxonomy

Hornets are closely related to yellow jackets, and together these two groups constitute the subfamily Vespinae within the family Vespidae, which includes all the social wasps. True hornets belong to the genus Vespa, while yellow jackets belong to the genera Vespula and Dolichovespula. Distinguishing between hornets and yellow jackets can be confusing, and some yellow jacket species are referred to as hornets, such as the bald-faced hornet (D. maculata). The most common distinction is that, in general, hornets build nests aboveground, while yellow jackets tend to build nests underground. There is an expectation that yellow jackets have more yellow coloration in their patterning, while hornets have more black, but this is not always the case.

Eusociality

All true hornets are social wasps, and like other related social insects, such as ants and bees, hornets have a caste system that defines the roles within a colony. A hornet colony revolves around a queen—the only female in the colony that sexually reproduces. Infertile females in the colony are called workers, whereas males are called drones. Colonies are founded by a queen who lays both fertilized and unfertilized eggs. The queen’s fertilized eggs develop into workers who expand, protect, and feed the nest. In contrast, unfertilized eggs develop into drones, the males that mate with the queen. Workers and drones typically lead short lives of only a few weeks or months, and, in places where winters are cold, they do not survive it. Queens may live up to a year, hibernating through the winter as needed to establish a new colony in the spring. Worker wasps can sometimes develop into queens if a colony’s queen dies or if the queen fails to maintain her dominant position. (See also eusocial species.)

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Like other social wasps, hornets make communal nests out of a paperlike substance made from wood pulp and saliva. A queen will begin a new nest with a small brood comb consisting of just a few cells, which is expanded once workers have been produced. Often, hornets’ nests are made within a tree or hanging from it, though they may also be constructed within the walls or ceilings of buildings. These nests are often dangerous to human beings because hornet workers may defend them aggressively. Like other wasps, hornets can sting repeatedly, and their stings are painful and venomous, but the venom of most hornet species is no more dangerous than that of other wasps. However, the venom contains histamines that can trigger allergic reactions. One of the most severe of these is anaphylactic shock, which is sometimes fatal.

Northern giant hornet

True hornet species are not native to North America, but at least two species have been introduced. The best known is the European hornet (V. crabro), which was introduced during the 19th century and has become well established in the eastern part of the continent. The northern giant hornet (V. mandarinia) was first reported in western Canada in 2019. Like other wasps, it is a predator species that aggressively hunts other insects, in particular honeybees (Apis mellifera), heightening the concerns of wildlife officials that it might damage already-stressed honeybee populations. Due to its size, which ranges generally from about 3.8 to 5 cm (1.5 to 2 inches) long—with workers being considerably smaller than the queen—the species poses some danger to people. Though its venom is not the most toxic among wasps, the volume that it can inject is large enough that multiple stings delivered by a swarm could be deadly, even to victims who are not allergic to wasp stings. It also possesses an unusually long stinger that is capable of piercing thick clothing, including typical beekeeping gear. Together, these factors have caused some researchers and people in the media to refer to the hornet as the “murder hornet”; however, this nickname has been criticized as alarmist.