Convergence in the ovipositor system of platygastroid wasps (Hymenoptera)

Abstract

It is widely accepted that there are two ovipositor system types in Platygastroidea. The Scelio-type ovipositor system features telescoping conjunctiva between metasomal tergites 6 and 7 and operates via internal changes in hydrostatic pressure alone, whereas muscles are involved in ovipositor extension and retraction in the Ceratobaeus-type. We here provide analyses of ovipositor systems in two platygastrine genera that cannot be classified as either Scelio- or Ceratobaeus-type, but exhibit telescoping conjunctivae and extend the ovipositor system without musculature. These represent unique derivations that are clearly identifiable by the location of the telescoping conjunctiva. In Gastrotrypes Brues, the telescoping conjunctiva occurs between T5 and T6, and in Platygaster tubulosa Brues it occurs between each segment from T3 to T6. If there are convergent derivations of a Scelio-type ovipositor system within Scelionidae (sensu Masner 1976), their identification will require examination of new characters, one of which we provide here, the presence and form of a ring of acanthae on the conjunctiva between T6 and T7.