Chalcidoidea are a large and diverse group of parasitoid wasps with more than 400,000 estimated species distributed among 19 families and more than 80 subfamilies. Despite the economic importance of this group, their taxonomy and classification is still very incomplete. A pair of specialized placoid sensilla located on the scutellum are known to exist only in the families Aphelinidae, Encyrtidae, Mymaridae, Signiphoridae and Trichogrammatidae. The shape and placement of the sensilla in relation to each other, and to the primary scutellar setae, is of taxonomic significance both at the species level and at high taxonomic levels. A survey of their distribution across Chalcidoidea is being conducted to assess the general arrangement, distribution, and presence of the sensilla as well as their potential homology. Following Patterson’s proposed tests of homology, similarity and conjunction will be tested by mapping the position and shape of the sensilla across Chalcidoidea and conducting detailed morphological studies of the sensilla for the five families. Congruence will be tested by mapping character distribution using phylogenetic hypotheses from both morphological and molecular data.