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The Ichneumonoidea comprises a huge group (over 100,000 estimated species worldwide) of primarily parasitoid insects that attack other arthropods, especially the immature stages of other insects (Gauld and Bolton, 1988; Wahl and Sharkey, 1993). A few taxa are secondarily phytophagous, and several groups that attack egg masses or food provisions of other arthropods are difficult to classify as either "parasitic", predaceous or parasitoid. The species of Ichneumonoidea vary tremendously in size, from approximately 1 mm in length to 5-6 cm (even larger if the ovipositor of some larger species is included).
The superfamily currently is considered to contain two extant families, Braconidae and Ichneumonidae, as well as one fossil family (Eoichneumonidae), and a fossil genus, Tanychora, of uncertain relationship to the other families (Sharkey and Wahl, 1992). Past classifications have sometimes included other groups, such as Stephanidae and Megalyridae, now transferred elsewhere, or they have recognized subfamilies of Braconidae (e. g. Aphidiinae and Apozyginae) and Ichneumonidae (Agriotypinae and Paxylommatinae) as distinct families.
Ichneumonoidea have been present since at least the early Cretaceous, being represented by Tanychora from Transbaikalia (Townes, 1973), as well as several genera of Eoichneumonidae from Australia, Siberia and Mongolia (Jell and Duncan, 1986; Rasnitsyn and Sharkey, 1988). The placements of the early Cretaceous Praeichneumon townesi as an ichneumonoid and of Eobracon inopinatus as a braconid (Rasnitsyn, 1983) have been questioned recently (Sharkey and Wahl, 1992; Whitfield, 2002); nevertheless it is clear that the superfamily was still represented at least by extinct groups from the very early Cretaceous.