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Insects utilize sound for various purposes such as communication, attack, defense and mating. In the case of cicadas, the song is used by males to attract females and thus perform copulation. “The cicadas’ song is produced by an organ at the base of the abdomen, a kind of acoustic box, which has a vibrating membrane”, says agronomist engineer Sinval Silveira Neto, from the Luiz de Queiroz Higher School of Agriculture (Esalq), in Piracicaba. (SP). Females also have this same organ, but without the vibrating membrane, which makes it impossible to produce sound. In addition to the cicada – which belongs to the order Homoptera -, crickets, grasshoppers and hopes, all of the order Orthoptera, also produce sounds (see the table below). As the song is only used during the reproductive season, cicadas only emit it in the adult stage. During periods of this animal symphony, the males settle on top of the plants, usually at dawn or dusk, and sing incessantly in search of a mate.
Typical insect noise is produced by the vibration of an internal air pocket
1 – In the abdomen of the male cicada there is the cymbal organ. It has muscles that are contracted when the insect wants to emit its characteristic sound to attract females.
2 – When these muscles contract, they make a kind of acoustic box vibrate inside the cicada, an air pocket surrounded by a membrane
3 – It is this vibration that produces the typical sound of the male cicada. Females have an atrophied cymbal organ and lack the vibrating membrane, so they don’t emit the sound.
Grasshopper and hope make more strident sounds than the cicada and the cricket
Insect – Cicada
How it makes sound – Organ in the abdomen
Frequency* – 4 to 5 kHz
Insect – Cricket
How it makes sound – Wing friction
Frequency* – 4 to 5 kHz
Bug – Hope
How it makes sound – Wing friction
Frequency* – 11 to 12 kHz
Insect – Grasshopper
How it makes sound – Wings rubbing against legs
Frequency* – 17 to 18 kHz
* The higher the frequency, the sharper the sound.