The orbicula (manubrium) is a dorsal sclerite between the tarsal claws in the Hymenoptera. Its detailed external morphology was surveyed throughout the order using scanning electron microscopy. Four types of presumed mechanosensory sensilla were found: two sensilla trichodea and two sensilla campaniformia. Variation in number, shape, orientation, and associated structures are discussed in the light of current phylogenetic hypotheses. There are generally two sensilla trichodea A on each orbicula, and this is a putative synapomorphy for all of Hymenoptera excluding the Xyelinae. The presence of a single sensilla trichodea A with a marked socket is postulated as a synapomorphy for the Chalcidoidea, Mymarommatidae, Diapriidae, an undescribed New Zealand family of Proctotrupoidea, and possibly Ceraphronidae. Arrangement of the sensilla trichodea B in a single row supports a putative clade comprising the Chalcidoidea, Mymarommatidae, Ceraphronidae, Cynipoidea, Diapriidae, Platygastridae, and the undescribed New Zealand family. Presence of a spur at the base of the sensilla trichodea B is a putative synapomorphy for the Chalcidoidea and the undescribed New Zealand family. Possession of sensilla campaniformia type B suggests a clade comprising Chalcidoidea, Diapriidae, and Scelionidae.