How the 'mute' cicada sings
"Mute" cicadas may use the sound of wing impact to communicate, according to a study published February 25, 2015 in the open-access journal PLOS ONE by Changqing Luo from Northwest A&F University, China, and colleagues.
Most male cicadas use specialized physical mechanisms, like the tymbal and/or the stridulatory organs, to produce loud and diverse sounds for communication. "Mute" cicadas from the genus Karenia do not have any specialized sound-producing structures, but the name is somewhat misleading, as they are still able to produce sounds. The authors of this study analyzed sounds produced by the male cicadas and their body shape to investigate how a species of "mute" cicada K. caelatata emits acoustic signals, as well as determine their function in communicating with other cicadas.
The researchers discovered that K. caelatata produces wing impact sounds by banging the forewing costa against the operculum, in what may be a newfound sound-production mechanism for cicadas. They also found that the body parts used to produce the sound had a modified shape when compared to cicadas with tymbal or stridulatory organs. The acoustic playback and behavioral observations suggest that the wing impact sounds of K. caelatata are used in communication with cicadas and function as calling songs. The newfound sound-production mechanism expands our knowledge on the diversity of acoustic signaling behavior in cicadas, and indicates the need for more bioacoustic studies on cicadas that lack the tymbal mechanism.