Moths produce extremely quiet ultrasonic courtship songs by rubbing specialized scales

Abstract

Insects have evolved a marked diversity of mechanisms to produce loud conspicuous sounds for efficient communication. However, the risk of eavesdropping by competitors and predators is high. Here, we describe a mechanism for producing extremely lowintensity ultrasonic songs (46 dB sound pressure level at 1 cm) adapted for private sexual communication in the Asian corn borer moth, Ostrinia furnacalis. During courtship, the male rubs specialized scales on the wing against those on the thorax to produce the songs, with the wing membrane underlying the scales possibly acting as a sound resonator. The male's song suppresses the escape behavior of the female, thereby increasing his mating success. Our discovery of extremely low-intensity ultrasonic communication may point to a whole undiscovered world of private communication, using ''quiet'' ultrasound.acoustic communication ͉ hearing ͉ playback experiment ͉ receiver bias ͉ sound-producing organ

New model for gain control of signal intensity to object distance in echolocating bats

“…Animals having a 'private' conversation with a conspecific close by emit very silent signals (Nakano et al, 2008), whereas animals communicating over large distances in general emit loud signals (e.g. Naguib and Wiley, 2001).…”

Double meaning of courtship song in a moth

“…Nearly all males produce a long pulse of 297-381 ms duration (95% confidence interval (CI), n ¼ 66). Therefore, females of this species, as well as those of the Asian corn borer, accept most of the normal singing males [7,18,19,21]. As shown in figure 1b and the electronic supplementary material, movie S1, which depict female mate acceptance to artificial long ultrasounds, wing-raising seemed to be an inevitable response to a long pulse of more than 200 ms. We cannot confirm the mechanism of this response, but signal processing via the central nervous system must be involved because decapitated or mated females never raise their wings.…”

“…In some moths with the deceptive song, a male emits ultrasonic signals that provoke a female's freeze response, which is also seen as a defence against attacking bats. For example, to increase their opportunities for copulation, singing males of the Asian corn borer, Ostrinia furnacalis (Pyraloidea, Crambidae), exploit the female's freeze response to ultrasound [7,18,19,21]. This mechanism is probably also present in the common cutworm, Spodoptera litura (Noctuoidea, Noctuidae), because mating is achieved even when bat-like sounds are broadcast instead of male songs [20].…”

Mechanical tuning of the moth ear: distortion-product otoacoustic emissions and tympanal vibrations

“…Under pure-tone stimulation, both cell types exhibit identical tuning curves that differ by ~20dB in sensitivity; A1 is the most sensitive receptor (Suga, 1961;Coro and Pérez, 1993). However, when describing moth hearing, the neural tuning curve of the A1 cell serves as the standard (Skals et al, 2005;Fullard et al, 2008;Lane et al, 2008;Nakano et al, 2008;Jackson et al, 2010). Neural audiograms indicate that moth ears are broadly tuned with low Q 10dB (<2) values and frequencies at minimum threshold between 20 and 50kHz (Fullard, 1982;Surlykke, 1986).…”

“…These moths are generally unpalatable after the accumulation of defensive compounds, frequently noxious by virtue of their capacity to irritate, damage, poison and/or drug potential predators (Hristov and Conner, 2005). In some of these species, the acoustic communication between moths is ecologically more relevant than bat-to-moth communication and accordingly, their hearing capabilities correlate with the acoustic features of conspecific mating sounds (Coro and Pérez, 1993;Sanderford et al, 1998;Nakano et al, 2008). In either acoustic interaction, i.e.…”