Annotated illustrations of hearing organ forms. Figures reproduced and adapted from Yager and Svenson (2008). A Parasphendale agrionina Gerstaecker, 1869 ♂ DK form hearing organ B Mantoidasp. ♀ MSMT form hearing organ C Parasphendale agrionina ♀ DNK form hearing organ D Angela Serville, 1839 ♂ MSMT form hearing organ E Tarachodes afzelii (Stål, 1871) ♀ DO form hearing organ F Hymenopus coronatus ♀ MESO form hearing organ. Asterisks indicate the ventral rod (B–F), which is not visible in the DK form (see Yager and Svenson 2008). Orange arrows indicate the knob, present on DK and DNK forms, barely visible in DO forms, and not present in MSMT forms. Blue arrows indicate opening to the auditory chamber. Abbreviation: kn = knob.