ABSTRACT
Wasps, along with ants, bees and sawflies, form the Hymenoptera, one of the largest orders of insects, with an estimated 300,000 species world-wide. Parasitic wasps are important natural enemies of insects and certain other small arthropods, including spiders, and they are a major factor in maintaining balanced ecosystems in terrestrial habitats throughout the world. Parasitoid wasps are either idiobionts or koinobionts, depending on the parasitic strategy adopted by the species concerned. Encyrtid wasps sometimes feature in classical biological control programmes. Seed-wasps aside, members of the Torymidae are associated with insect-induced plant galls, usually as parasitoids. Braconid wasps tend to be smaller than ichneumonids, and although most are endoparasitic koinobionts, many are either ectoparasitic idiobionts or egg–larval parasitoids. The role of ichneumonid wasps as beneficial insects in European field crops is highlighted in brassicaceous seed crops, where such parasitoids attack a range of harmful insects, including flea beetles, pollen beetles and ceutorhynchid weevils.
