Fig. 1. (A) Close-up of the tympanum of the ear of Noctua pronuba. An opaque membrane, the conjunctivum (Cj), is situated distally from the tympanic membrane (TM), both of which lie above the tympanic cavity at the posterior lateral margin of the metathoracic segment. The stigma (arrow) marks the attachment site of the auditory receptor organ. Scale bar, 0.25 mm. (B) Morphological features of the tympanal system, highlighted as they pertain to the vibrational characteristics of the tympanum. The TM, sensu stricto, is bordered distally by a nodular sclerite, the epaulette (Ep), which separates it from the Cj. The attachment site of the auditory chordotonal organ (arrow in A) appears as a dark spot at the centre of the opaque zone (OZ), which is surrounded by the transparent zone (TZ).