That rhythm unmistakable and persistent that accompanies us on warm days from June to September – unlike crickets, which chirp in the dark – is the sound emitted by cicadas which, contrary to what Aesop’s famous fable “the ant and the grasshopper” says, are insects particularly active. But why do we only hear them in the summer? cicadas they are chirping only in summer because their I singproduced by males to attract females femalesis only possible when the temperature exceeds the 22 °C. This is due to the fact that their organ stridulatorcomposed of thin sheets called timbalescan vibrate and produce sound only at temperatures high. When it is cold or rainy, the cicada’s diaphragm loses elasticity and the insect cannot sing. In this article we discover the “song” of cicadas, which species are present in Italy and Europe and what their life cycle is.
Why Cicadas Only “Sing” When It’s Hot
Reproduction is the crucial moment in the adult stage of a cicada and lasts a few weeks. The characteristic and exhausting sound, called to chirp, It is produced by males to attract females and is emitted only when it is hot for a very specific reason: the male has a organ stridulatorcomposed of a series of thin sheets, called timbales.
To produce sound the cicada must vibrate these sheets, but this is only possible when the room temperature reaches at least 22°C. When it rains or the temperature drops, the diaphragm loses elasticity and the insect stops singing. The chirping of the cicada is a sound species-specificwhich means that each species emits its own call at a specific wavelength and with a rhythm distinguishable only by females of the same species.
In fact, many entomologists distinguish the different species by recording their song and analyzing its frequency. cicada more noisy to the world is an African cicada brevis which reaches the 106.7 decibels. The whole mechanism of sound culminates with the moment of reproduction; once the eggs are laid at the end of the summer the adults die en masse and to hear the cicadas again we will have to wait for the heat of the following summer.
Where are cicadas found?
Cicadas represent a complex of over 3,000 species spread throughout the world, belonging to theOrder Hemiptera. They prefer environments arid with the presence of woods And bushesmixed with open and sunny areas. They are found mainly on pine and olive trees, but they also appreciate other trees and shrubs. The most common cicada in the whole Mediterranean area is the Ash Cicada (Cicada orni) which has a very strong and characteristic “song”, while one of the most widespread species throughout Europe is the Mountain Cicada (Mountain Cicadette) which also populates areas of Scandinavia thanks to the fact that its larval stage can tolerate even rather rigid winter temperatures.
The life cycle of cicadas
The life cycle of the cicada is divided into an underground evolutionary phase and an adult phase that lives on trees and shrubs. The immature stage, of nymphas soon as it hatches from the egg, it burrows into the ground and lives underground for several years, feeding on the sap extracted from the roots of plants, until it reaches an appearance very similar to the adult but still without wings.
At this point, thanks to a pair of burrowing front legs, it emerges from the ground to climb onto a plant and molt; from the transparent exoskeleton of the nymph emerges an adult individual ready to fly and reproduce.
Some species, the so-called annual cicadaslive underground in the nymph stage for periods ranging from two to five years. Other species, called periodical cicadashave the peculiarity of spending a large part of their life underground for many years, and then emerging from the ground all together at very precise intervals.
The most surprising case is that of some species of cicada from North America, of the genus Magicicada that live in the ground at the nymph stage for a period ranging from 13 to 17 years and then emerge all at once by the thousands, sometimes with densities of 350 individuals per square meter. A phenomenon that scares and fascinates at the same time.
