The Waterston’s evaporatorium of Ceraphronidae (Ceraphronoidea, Hymenoptera): A morphological barcode to a cryptic taxon

Abstract

The Waterston’s evaporatorium (=Waterston’s organ), a cuticular modification surrounding the opening of an exocrine gland located on metasomal tergite 6, is characterized and examined for taxonomic significance within the parasitoid wasp family Ceraphronidae. Modification of the abdominal musculature and the dorsal vessel are also broadly discussed for the superfamily Ceraphronoidea, with a novel abdominal pulsatory organ for Apocrita being discovered and described for the first time. Cuticular modification of T6, due to the presence of the Waterston’s evaporatorium, provides a character complex that allows for genus- and species-level delimitation in Ceraphronidae. The matching of males and females of a species using morphology, a long standing challenge for the group, is also resolved with this new character set. Phylogenetic analysis including 19 Waterston’s evaporatorium related characters provides support for current generic groupings within the Ceraphronidae and elaborates on previously suggested synapomorphies. Potential function of the Waterston’s organ and its effects on the dorsal vessel are discussed.