Grooming behaviours from representatives of 36 families of Hymenoptera were video recorded and analysed. Thirty-three distinct types of grooming movements were recognized. The evolutionary pattern of each behaviour is discussed. Some behaviours displayed consistent variation between taxa, and appear to be informative regarding higher lever relationships within the order. Putative synapomorphies are reported that support the monophyly of the Apocrita, Cynipoidea, Platygastroidea, Ichneumonoidea, and Chalcidoidea including the Mymaridae. (C) 1999 The Linnean Society of London.