Representatives may be social or solitary, free or parasitic. They are insects with two pairs of wings, the forewings and hindwings being interlocked by means of hooklets. The wing venation is often reduced and the hindwings are usually smaller. The abdomen is usually constricted forming a 'waist'.
Metamorphosis is complete, and the larvae are usually without legs.
Pupae are usually in a cocoon. Parthenogenesis is frequent, in some cases giving rise only to males but in others producing females as well. 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.