Hornets are the largest eusocial wasps, reaching up to 45 millimetres (1.8 inches) in length. The true hornets make up the genus Vespa, and are distinguished from other vespines by the width of the vertex (part of the head behind the eyes), which is proportionally larger in Vespa; and by the anteriorly rounded gasters (the section of the abdomen behind the wasp waist). See wasp and bee characteristics to help identify an insect.
The genus Vespa comprises about 20 species, most of which are
native to tropical Asia, but there is a species found across
temperate Eurasia from Britain to Japan, the European hornet (V.
crabro), and another, Oriental hornet (V. orientalis), that
extends via southern and central Asia to the Arabian peninsula,
up to northern and eastern Africa and the Mediterranean basin
(including southern Italy and Sicily). Another occurs in
temperate eastern Asia, Yellow hornet (V. simillima), and some
tropical species also range as far north as China, Siberia, or
Japan. The Asian giant hornet (V. mandarinia) is a native of
temperate and tropical Asia. The European hornet V. crabro, has
been accidentally introduced to North America and is present in
many eastern regions.
The structure of the nestIn Vespa crabro, the nest is founded in spring by a fertilized female, known as the queen. She generally selects sheltered places like hollow tree trunks. She builds a first series of cells (up to 50) out of chewed tree bark. The cells are arranged in horizontal layers named combs, each cell being vertical and closed at the top. An egg is then laid in each cell. After 5-8 days it hatches, and in the next two weeks the larva undergoes its five stages. During this time the queen feeds it a protein-rich diet of insects. Then the larva spins a silk cap over the cell's opening, and during the next two weeks transforms into an adult, a process called metamorphosis. Then the adult eats her way through the silk cap. This first generation of workers, invariably females, will now gradually undertake all the tasks that were formerly carried out by the queen (foraging, nest building, taking care of the brood, etc) with one exception: egg-laying, which remains exclusive to the queen.
As the colony size grows, new combs are added, and an envelope is built around the cell layers, until the nest is entirely covered, with the exception of an entry hole. At the peak of its population the colony can reach a size of 700 workers. This occurs in late summer.
At this time the queen starts producing the first reproductive individuals. Fertilized eggs develop into females (called "gynes" by entomologists), unfertilized ones into males (sometimes called "drones"). Adult males do not participate in nest maintenance, foraging, or caretaking of the larvae. In early to mid-autumn they leave the nest and mate during "nuptial flights". Males die shortly after mating. The workers and queens survive at most until mid to late autumn; only the fertilized queens survive over winter.
Other temperate species (e.g. the yellow hornet V. simillima or the Oriental hornet V. orientalis) have similar cycles. In the case of tropical species (e.g., V. tropica), life histories may well differ; and in species with both tropical and temperate distributions (such as the Asian giant hornet Vespa mandarinia), it is conceivable that the cycle depends on latitude.
A Hornet's sting is harmful, however the sting toxicity varies greatly by hornet species - from a typical sting, to among the most venomous known insects. Allergic reactions can occur, these may result in death depending on the severity.
This Hornet Page is Copyright The Animal Web Guide © 2004 - 2009 Chuck Ayoub