The anatomical cluster that consists of the apical regions of the left and right first valvulae, which are interlocked with each other in a manner similar to how the first and second valvulae are connected by olistheter.
written by: Eggs, B., S. Fischer, M. Csader, I. Mikó, A. Rack, and O. Betz. 2023. Terebra steering in chalcidoid wasps. Frontiers in Zoology 20:26.
