Similar but distinct ovipositor steering mechanisms in members of the parasitic wasp families Gasteruptiidae and Aulacidae are described. In both of these there are abrupt stops near the apex of each of the upper and lower ovipositor valves. These stops, which are closely apposed when the ovipositor is at rest, prevent the lower valves from being extended posteriorly relative to the upper valve. Attempts to extend the lower valves posteriorly force the ovipositor to bend dorsally. This ability to manipulate the ovipositor tip allows the wasps to locate their eggs more precisely in or near their hosts. In the Gasteruptiidae the stops are opposed, raised bosses which project laterally from the main ovipositor shaft. This mechanism is clearly visible externally in intact ovipositors. In the Aulacidae, the pre-apical stops are formed by the abrupt termination of a longitudinal ridge on each lower valve and of grooves on the upper valve. The ridges run within the grooves and the mechanism is not visible externally. The implications of these mechanisms for the classification of these two families are discussed.