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Bethylidae

Very small parasitoid wasps. Males winged, wings rarely reduced, females winged, wingless or with reduced wings. Adults usually black. The adults are active from April until October, but mainly during the summer months. They are external parasitoids on beetle or lepidopterous larvae. The host is rapidly paralysed and may be killed. It may be dragged or carried to a concealed place, or may already be in a concealed place, e.g. within rolled leaves or under bark. One or more eggs are laid on the host. The larvae feed externally on the host. The female may stay with the larvae until they mature. Females probably over-winter as adults. Nationally: 9 genera with 14 native species, with a further species restricted to the Channel Islands, and several introduced species associated with granaries and storehouses.

Chrysididae

These solitary wasps are often called cuckoo, or ruby-tailed, wasps. They have a heavily armoured, brightly coloured cuticle. The apical gastral segments have been modified to form a thin, tubular structure that can be telescoped into the hind end of the gaster. In the female this tubular structure has been secondarily modified to act as an ovipositor. They have a parasitoid life history.

Embolemidae

Small reddish-brown parasitoid wasps. Males are winged, females wingless. The adults are active from August until October and the females again during April and May. One British species with an unknown natural history.

Pompilidae

Solitary species known as spider, or spider-hunting, wasps. With their long legs they are usually seen making short rapid movements across bare ground and through short vegetation during warm, sunny weather. The female hunts for spiders as food for the larvae. See Day (1988) for details of prey. One spider is provided for each larva. The female paralyses its prey and then usually carries or drags it across the ground to a place for temporary concealment or to a previously prepared nest site. Once the prey is in a cell an egg is laid on it and often the burrow to the cell is blocked. On hatching, the larva punctures the host's body and begins to suck its internal fluids. The spider eventually dies. Over-wintering is usually as a mature larva. There may be one or several generations a year. Nationally: 15 genera with 44 species (2 species restricted to the Channel Islands). Nine of the genera have been selected for further comment.

Sapygidae

Medium-sized to large wasps. Black, often with red, yellow or white markings. The larvae are cleptoparasites on solitary bees of the genera Osmia and Chelostoma. The female introduces an egg into the cell of its host by using her sting to penetrate the cell wall. On hatching, the first instar larva, although without legs, is active and destroys the host's egg with its large mandibles. The larva then moults into the next instar which has smaller mandibles and feeds on the host's provisions. Probably one generation a year. Nationally: 2 genera with 2 species.

Wasp

There are eleven families of wasps, split between the superfamilies Vespoidea and Apoidea. These are the Dryinidae, Embolemidae, Bethylidae, Chrysididae, Tiphiidae, Mutillidae, Sapygidae, Pompilidae, Sphecidae, Crabronidae and Vespidae. Most of the species are solitary and each family or group of solitary species specialises in a particular type of prey, e.g. flies, spiders, aphids, caterpillars. Some species do not build a nest for their brood but utilise natural crevices such as beetle borings, hollow plant stems or holes in masonry, while others excavate their own nests in suitable substrate such as dead wood or sand or friable soil. Prey is usually paralysed or killed by stinging and is then dragged or carried to the nest. Some species are cleptoparisitic on other species of wasps and so do not build a nest of their own, but lay their eggs in the nests of other solitary species. Some primitive species, after causing temporary paralysis of their prey by stinging it, lay their eggs directly on the bodies of the target host species. The host recovers and carries on with its normal behaviour but eventually dies due to the developing wasp. The more familiar social species construct their nests from chewed-up wood pulp and locate them underground, in hollow trees and roof-spaces. Others are hung in suitable trees and under eaves of houses. While most wasps hunt for suitable prey to either provision their nests or to feed directly to their young, the adults cannot digest large fragments of  food material, as it will not pass through their narrow waist and into the digestive system. For this reason adult wasps exist largely on a semi-liquid diet consisting of nectar, honeydew, sap, or insect haemolymph. Hunting for prey and nest building is carried out by the females.