This infraorder is defined by bionomic criteria rather than by morphological definitions. The species are ecto-or endo-parasitoids or parasites on arthropods or parasites of different living plant tissue. The Parasitica include parasitic wasps, gall wasps, fig wasps, chalcid wasps, and their allies.
The ovipositor retains its egg-laying function in the Parasitica, and the female deposits her egg into the host. The wing venation is reduced in most cases. The leg has an extra segment at its base, the trochantellus, located between trochanter and femur.
The Parasitica are distributed worldwide, with the exception of Antarctica and other environments with extreme conditions. The classification of the Parasitica has not been completely resolved; more research on fossilized taxa would probably bring greater clarity. The following grouping of superfamilies within the Parasitica is rather conservative: Ichneumonoidea, Trigonaloidea, Megalyroidea, Evanioidea, Proctotrupoidea, Ceraphronoidea, Chalcidoidea, and Cynipoidea.