The antenna cleaner in gall-inducers, inquilines and parasitic cynipoid wasps: a comparative study

Hymenoptera evolved structures on the legs which are able to remove particles from their antennae through grooming behaviour. The antenna cleaner (strigil) consists of an apical and modified protibial spur (calcar, composed of a trunk and a velum) and a modified basitarsus including a fine comb made up of setae and a notched inner surface. In “Terebrantia”, the non-aculeate Apocrita, large comparative studies of strigil are scarce, especially within lineages. Here, we studied in detail this structure in Cynipoidea, a group of wasps including parasitoids (Ibaliidae, Liopteridae and Figitidae), gall-inducers (Cynipidae) and gall-inquilines (Cynipidae), through a SEM analysis. We found some traits quite conserved across species and lineages. For example, the shape of protibia is almost invariably broadening towards apex, and one single, straight rather than curved, dorso-apical socketed spur on apical margin of protibia occurs in almost all species. Other characters roughly differentiate families. For example, thick and long setae on the protibia are arranged in one row especially in Figitidae, Ibaliidae and Liopteridae, while they more often occur in more than one rows in Cynipidae, which was the family with the shortest calcar. Figitidae have shorter basitarsal notch, but had longer and denser setae on the notch, compared with Cynipidae and Ibaliidae. Further characters were extremely variable across and within lineages. The observed morphological variation did not seem to reflect the phylogeny of Cynipoidea, and a role of life-history traits on such variation was not suggested, at least with the methodological approach used here.