Hornet  (Vespa crabro)

Common only in parts of south England (3).

The hornet is an impressive insect, and is Britain's largest social wasp (4). Despite its rather fearsome appearance, it is rarely aggressive (1); this species has been much maligned and will usually only attack if the colony is threatened. Queens (reproductive females) are larger than males and workers (non-reproductive females. The head features large, c-shaped eyes, robust antennae and three simple eyes or 'ocelli' arranged in a triangle between the main eyes (2). The thorax and abdomen are separated by a distinct 'wasp-waist', and there are alternating bright orange-yellow and brownish-black stripes along the abdomen. There are two pairs of wings, which are joined together by means of tiny hooks, giving the appearance that there is just one pair of wings (2).

This species was considered rare in Britain in the 1960s, but it has since made a recovery and has become fairly common in some parts of the south of England. It seems to be spreading northwards and reached south Yorkshire in 1985 (1). It is found throughout Europe, but it is rare in many parts of Germany and is even threatened with extinction in some areas of central Europe (2). This species also occurs in Asia and Madagascar, and has been introduced to the United States and Canada (2).

Hornets nest in hollow trees, wall cavities, chimneys and similar structures (1). They show a preference for wooded areas (3).

Queens emerge from hibernation during the spring, and they search for a suitable location in which to start a new nest (2). She begins to build the nest with chewed wood pulp, and a few eggs are laid in individual paper cells; these eggs develop into non-reproductive workers. When 5-10 workers have emerged, they take over the care of the nest, and the rest of queen’s life is devoted solely to egg laying (2). Hornet workers capture insects, bringing them back to the nest to feed the brood. Most people do not realise that hornets control many species of insect pests, and their presence in a garden should be welcomed (2). Workers need more high-energy sugary foods such as sap and nectar, and hornet larvae are able to exude a sugary liquid which the workers can feed on (2).

The nest grows throughout the summer, reaching its peak size towards mid September. At this time the queen lays eggs that develop into males (drones) and new queens, she then dies shortly after. The new queens and males mate during a 'nuptial flight', after which the males die, and the newly mated queens seek out suitable places in which to hibernate; the old nest is never re-used (2).

In parts of Europe this beautiful wasp is threatened as a direct result of persecution by humans (2).

This species has a bad public image, yet it is generally a peaceful, non-aggressive species. More needs to be done to educate the public about this fascinating insect (2).

For more on invertebrates and their conservation see Buglife, the invertebrate conservation trust:
http://www.buglife.org.uk/

• Abdomen: in arthropods (crustaceans, insects and arachnids) the abdomen is the hind region of the body, which is usually segmented to a degree. In crustacea (e.g. crabs) the limbs attach to the abdomen; in insects the limbs are attached to the thorax (the part of the body nearest to the head) and not the abdomen. In vertebrates the abdomen is the part of the body that contains the internal organs (except the heart and lungs).
• Antennae: pair of sensory structures on the head of invertebrates.
• Hibernation: a winter survival strategy characteristic of some mammals in which an animal's metabolic rate slows down and a state of deep sleep is attained. Whilst hibernating, animals survive on stored reserves of fat that they have accumulated in summer. In insects, the correct term for hibernation is 'diapause', a temporary pause in development and growth. Any stage of the lifecycle (eggs, larvae, pupae or adults) may enter diapause, which is typically associated with winter.
• Larvae: stage in an animal's lifecycle after it hatches from the egg. Larvae are typically very different in appearance to adults; they are able to feed and move around but usually are unable to reproduce.
• Thorax: part of the body located near the head in animals. In insects, the three segments between the head and the abdomen, each of which has a pair of legs.

1. National Biodiversity Network Species Dictionary (March 2003): http://www.nhm.ac.uk/nbn/
2. The hornet (March 2003): http://www.vespa-crabro.de
3. Sterry, P. (1997) Collins Complete British Wildlife Photoguide. Harper Collins Publishers Ltd., London.
4. Buczacki, S. (2002) Fauna Britannica. Hamlyn, London.