Cicada song
Problems listening to these files? See media help. Male cicadas have loud noisemakers called "tymbals" on the sides of the abdominal base. Their "singing" is not the stridulation (where one structure is rubbed against another) of many other familiar sound-producing insects like crickets: the tymbals are regions of the exoskeleton that are modified to form a complex membrane with thin, membranous portions and thickened "ribs". Contracting the internal tymbal muscles produces a clicking sound as the tymbals buckle inwards. As these muscles relax, the tymbals return to their original position producing another click. The interior of the male abdomen is substantially hollow to amplify the resonance of the sound. A cicada rapidly vibrates these membranes, and enlarged chambers derived from the tracheae make its body serve as a resonance chamber, greatly amplifying the sound. The cicada modulates the sound by positioning its abdomen toward or away from the substrate. Additionally, each species has its own distinctive "song".[1]
Average temperature of the natural habitat for this species is approximately 29 °C (84 °F). During sound production, the temperature of the tymbal muscles was found to be slightly higher.[10] Cicadas like heat and do their most spirited singing during the hotter hours of a summer day, in a roughly 24 hour cycle.
Although only males produce the cicadas' distinctive sound, both sexes have tympana, which are membranous structures used to detect sounds and thus the cicadas' equivalent of ears. Males can disable their own tympana while calling.[11]
Some cicadas produce sounds up to 120 dB (SPL)[11] "at close range", among the loudest of all insect-produced sounds.[12] This is especially notable as their song is technically loud enough to cause permanent hearing loss in humans, should the cicada sing just outside the listener's ear (unlikely). Conversely, some small species have songs so high in pitch that the noise is inaudible to humans.[13] Species have different mating songs to ensure they attract the appropriate mate. It can be difficult to determine from which direction(s) cicada song is coming, because the low pitch carries well and because it may, in fact, be coming from many directions at once, as cicadas in various trees all raise one another to make noise in unison. Although relatively loud, cicada song can be comforting and even hypnotic at times, as it is at its loudest during the hottest time of an already hot day.
In addition to the mating song, many species also have a distinct distress call, usually a somewhat broken and erratic sound emitted when an individual is seized. A number of species also have a courtship song, which is often a quieter call and is produced after a female has been drawn by the calling song.
[EDLIS Notes]
Two examples of the cicada song. Neither sound file gives one a complete idea of the din created by hundreds of them singing at the same time in an area.