Hearing in Butterflies: Neurophysiological Characterization of the Auditory Afferents in Morpho Peleides (Nymphalidae)

Many butterflies have well developed tympanal ears on their wings but little is known about what they are capable of hearing in their natural environments. The tympanal ear of many butterflies, including Morpho peleides, comprises an outer membrane and a conspicuous inner dome (tholus), both of which are innervated by two separate auditory nerve branches (NII and NIII) and their respective sensory organs. Using extracellular neurophysiological recordings, I explored how this morphology contributes to mechanical sound frequency and amplitude discrimination. I also show that the auditory nerves of M. peleides responded to playbacks of the broadband cyclic sounds produced passively during flight of blue jays (Cyanocitta cristata), as well as to the low frequency vocalizations of one of its main avian predators, the rufous-tailed jacamar (Galbula ruficauda), providing further evidence that butterflies and possibly other diurnal insects could be using their sense of hearing to detect and avoid avian predators.