Hornets (insects in the genus 'Vespa') are the largest of the eusocial wasps, and are similar in appearance to their close relatives yellowjackets. Some species can reach up to 5.5 cm (2.2 in) in length. They are distinguished from other vespine wasps by the relatively large top margin of the head and by the rounded segment of the abdomen just behind the waist.

Most species only occur in the tropics of Asia, though the European hornet ('Vespa crabro'), is widely distributed throughout Europe, Russia, North America and Northeast Asia. Wasps native to North America in the genus Dolichovespula are commonly referred to as hornets (e.g., baldfaced hornets), but are actually yellowjackets.

Adult hornets feed themselves with nectar and sugar-rich plant foods. Thus, they can often be found feeding on the sap of oak trees, rotting sweet fruits, honey and any sugar-containing foodstuffs. Hornets frequently fly into orchards to feed on overripe fruit. Hornets tend to gnaw a hole into fruit to become totally immersed into its pulp. A person who accidentally plucks a fruit with a feeding hornet can be attacked by the disturbed insect.

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