Invertebrates
Cicada
Cicadidae · also called cicadas, dog-day cicada
A cicada is the sound of summer given a body: a stout, big-eyed, clear-winged insect whose males fill the air with a shrill electric drone. It makes that noise not by rubbing anything but by clicking a pair of drumhead membranes hundreds of times a second in a hollow, amplifying abdomen. And it earns the racket the hard way, after years spent alone underground drinking sap from roots in the dark.
Overview
Cicadas are the family Cicadidae, around 3,000 species on every continent except Antarctica, most diverse in tropical and subtropical woodland and savanna. They feed only on plant sap for their whole lives — the nymphs on roots underground, the adults on twig xylem — so they never bite, chew, or eat leaves.
The song and the years underground
Only males sing, buckling ribbed tymbal membranes on the abdomen hundreds of times a second, with the hollow abdomen as a resonator; the loudest species hit about 120 decibels. After hatching, a nymph burrows and feeds on roots for 2 to 5 years — or exactly 13 or 17 years in the North American periodical cicadas — then climbs a trunk at night, splits its skin, and pulls out as a soft adult, leaving the empty brown shell behind. The winged adult lives only two to six weeks.
Not locusts
Despite the North American folk name, cicadas are not locusts. True locusts are swarming grasshoppers that strip crops; cicadas do not swarm to feed, eat no foliage, and cause only minor twig damage from egg-laying. Many emerge in vast synchronised broods that swamp every predator, so enough survive to breed.
Status
Not Evaluated and in no broad danger — widespread, abundant, and shielded by their underground life. Some small-range species are vulnerable, and periodical cicada broods, each tied to a defined region of mature forest, can be lost locally when that forest is cleared, since a paved-over brood cannot move.
Cicada: common questions
Why are cicadas so loud, and how do they make the sound?
The noise is a mating call produced only by males, and it comes from a mechanism unlike anything in crickets or grasshoppers. On each side of the base of the abdomen is a stiff, ribbed membrane called a tymbal. Powerful internal muscles pull the tymbal in so that it buckles with a click, then let it spring back with another click, and by doing this hundreds of times a second the cicada produces a continuous buzz or whine. The abdomen of a singing male is largely hollow and acts as an air-filled resonating chamber that amplifies the sound, and air sacs and the position of the wings tune it further. The largest species are among the loudest of all insects, reaching about 120 decibels, and males often call together in choruses that are louder still and that space the singers out and swamp predators.
How long do cicadas live?
It depends on whether you count the underground years. A cicada spends by far the longest part of its life as a nymph in the soil, feeding on roots, for between about two and five years in most species and for exactly 13 or 17 years in the North American periodical cicadas. The winged adult stage that people see and hear lasts only about two to six weeks, just long enough to moult, harden, sing, mate, and for females to lay eggs in slits cut in twigs before the adults die. So an annual or dog-day cicada may be four or five years old as an adult, and a periodical cicada is 13 or 17, but no cicada lives long once it has wings.
What is the difference between an annual cicada and a periodical cicada?
Annual cicadas, also called dog-day cicadas, appear somewhere every summer because their broods overlap, and although each individual takes two to five years underground, there are enough of them at different stages that adults emerge every year. They are usually larger and greener or browner. Periodical cicadas, found only in the eastern United States, are smaller, black-bodied, and red-eyed, and an entire brood across a region emerges in a single synchronised wave after precisely 13 or 17 years, then nothing for over a decade until the next generation. The periodical cicadas hold the record for the longest known insect development time.
Are cicadas dangerous, do they bite or sting?
No. Cicadas have no sting, and their mouthparts are a fine tube built for piercing plant tissue and sucking sap, not for biting animals. A cicada that lands on a person and is left alone will do nothing, and the only way to be nipped is to hold one for a long time, when it may occasionally probe a finger with its beak, mistaking it for a branch, which feels like a pinprick and draws no blood. Cicadas are harmless to people, pets, and gardens beyond the minor twig damage from egg-laying, and in many cultures they are eaten, the newly emerged soft adults being the preferred stage.