Resonant wing systems in the Australian whistling moth Hecatesia (Agarasidae, Lepidoptera)

DARWIN described the sound made by the forewings of the nymphalid Ageronia feronia as a click of a spring catch on a toothed wheel. Descriptions of the sounds produced by the Agarasidae, which have similarly modified forewings, have repeatedly invoked the rubbing of either the antennae or foretibia on the ribbed forewing2,3. Nicholson4 suggested that the production of sound in the whistling moth Hecatesia was percussive, with the knobs of each forewing (castanets) striking each other at the top of the flight stroke. I have confirmed the existence of such a percussive system in two species of Hecatesia. Recordings of H. exultans Walker and H. thyridion Feisthamel from the coastal sand plain of Western Australia revealed two patterns of sound corresponding to the respective flight behaviour of the two species.