Suborder Symphyta consists of the more primitive hymenopterans. The waist is not present and the ovipositor is adapted for sawing or boring. Parasitism is rare. Suborder Apocrita contains the majority of Hymenoptera with the typical 'waisted' appearance. There are a large number of parasitic families, all with the ovipositor adapted for piercing.
Several families produce galls on plants.
The Cynipidae, for instance, produce the familiar oak galls and also those on roses. Most are parasitic on other insect eggs, larvae, or pupae, and several are used for biological control of pests. The families are grouped in the superfamilies Trigonaloidea, Ichneumonoidea, including ichneumon flies, Evanioidea, Cynipoidea, including gall wasps, and Chalcidoidea. Most are small insects. The two superfamilies Proctotrupoidea and Bethyloidea also contain many species that are parasitic on other insects or form galls.