You hear it everywhere but hardly ever see it. The cicada is the sound of summer: that insistent chirring that sometimes keeps us from resting during the hottest hours. For the adult, though, the song is only the final act of a life spent mostly underground, in the dark.
What it looks like and which species live in Italy
The cicada is an insect of the order Hemiptera and the family Cicadidae, with a sturdy body, a broad head and transparent wings. Its colour ranges from grey to green and dark brown, and most species are between 2 and 5 cm long. There is no single “cicada”: Europe has more than 30 species. Three of those you can come across in Italy are:
- Ash cicada (Cicada orni): about 28 mm long on average, it is coloured brown, black and green with a greyish bloom, which camouflages it very well on bark.
- Common cicada (Lyristes plebejus): the largest in Europe, it has a black body of about 35 mm with ochre underparts. It lives in woodland and shrubland, on pines, oaks, olive trees and fruit trees.
- Mountain cicada (Cicadetta montana): widespread across Europe, it reaches as far as Scandinavia because its young stages can withstand quite harsh winters.
Why do cicadas only sing in summer?
Only the male sings, to attract the female. He does not use a voice or rub his wings together: the sound comes from the tymbals, elastic membranes on the sides of the abdomen that are made to vibrate by special muscles. Each species has its own call, so much so that entomologists also tell them apart by recording their songs.
There are two reasons for the summer timing. Adults only appear in the warm months, in Italy mainly between June and August, and they have just a few weeks to reproduce. They also need heat: the song is estimated to start above about 22 °C, because the membranes lose their elasticity in the cold. This is why cicadas are heard mostly during the hottest hours.
The life cycle: how long does a cicada live?
The adult usually lives for a few weeks, but the insect’s whole life lasts years. It all starts with mating, during which the two insects stay joined for several minutes. The female then uses her ovipositor to cut into the bark of twigs and brambles and lays her eggs inside. After reproducing, the adults die.
Small nymphs, often called larvae, hatch from the eggs, drop to the ground and burrow into the soil. They stay there for years, digging tunnels and feeding at the roots. Many species take 2 to 5 years, and the ash cicada is said to take about 3 years on average. The record holders are in North America: cicadas of the genus Magicicada stay underground for 13 or 17 years, then all emerge together.
When it is mature, the nymph leaves the ground and climbs a tree, still without working wings. There it moults for the last time and the adult emerges, leaving its exuvia, the empty casing, attached to the bark. Finding one of these “shells” in summer is often the easiest way to discover that there are cicadas nearby.
What do cicadas eat?
It feeds on plant sap, which it sucks up with piercing mouthparts: the nymph takes it from the roots, the adult from branches and trunks. This sap is low in nutrients, which helps explain why development takes so long.
What are the cicada’s predators?
As an adult it is preyed on mainly by birds, such as bee-eaters, while during its life underground it has to watch out for moles.
Are cicadas dangerous or harmful?
No, they are harmless to us: at most they disturb our rest. The effect on plants is also usually modest, and studies of North American cicadas show that large trees tolerate both the feeding and the cuts made for the eggs. Young plants can be more vulnerable.
Some people may find it hard to spot, but not to hear! Next time you hear one, follow the sound and look closely at the bark: it is there, perfectly camouflaged. You can find other small inhabitants of nature in my gallery of insects and in the macro world.
