Cicada

• 1. Introduction

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  Cicadas, the loud insects of the superfamily Cicadoidea, produced a rare coincidence in 2024. Two groups of periodical cicadas surfaced in the same year across the midwestern and eastern United States. One group keeps a 13-year underground clock, and the other keeps a 17-year clock. Their calendars line up only once every 221 years, and the last meeting before 2024 came in 1803. Most cicadas keep no such schedule. More than 3,000 species are described worldwide, and many more still lack a formal description. Why would an insect spend years beneath the soil and then live above it for under two months? How does a creature this small sing loudly enough to damage a human ear? And why did Homer, Aristotle and the artists of the Shang dynasty all pay attention to the same singer?

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• 2. Underground Years

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  Somewhere among the roots of an oak, willow or maple, a cicada nymph is digging a chamber with its strong front legs. There it drinks watery xylem sap, and its body and burrow become coated in its own fluid waste. In wet habitats, larger species build mud towers above ground to bring air into their burrows.

  Most cicadas go through a life cycle lasting 2-5 years. Annual cicadas can spend anywhere from one to nine or more years as nymphs. Because their adults do not emerge in step with one another, some members of each species appear every single year.

  The exit tunnel is the last thing a nymph digs. It climbs onto a nearby plant and molts for the final time. The empty exoskeleton, called an exuvia, stays clinging to the bark.

  The winged adult, known as an imago, measures 2 to 5 cm in most species. Its time in the light is short. Both males and females die within a few weeks of leaving the soil, and the natural adult lifespan is under two months. Folklore says adults do not eat, yet they do drink plant sap through sucking mouthparts, though only in very small amounts.

  In some species, males stay in one spot and call, sometimes together in a chorus. In others, males roam from place to place with quieter calls while they search for females. After mating, the female cuts slits into the bark of a twig and lays her eggs. When the eggs hatch, the tiny nymphs drop to the ground and burrow, and the cycle begins again. In one North American genus, that hidden stage runs far longer than any of these figures.

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• 3. Prime Number Clocks

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  Brood XIII of the genus Magicicada spends 17 years underground, while Brood XIX, in some parts of the region, spends 13. This genus is found only in North America. Its adults appear suddenly and briefly in enormous numbers, at intervals that can be predicted years ahead.

  One explanation points to predators such as the cicada killer wasp and the praying mantis. Suppose a specialist predator has a five-year life cycle. Against a 17-year cicada, its population would peak at an emergence only every 85 years, which is 5 times 17. A cicada on a 15-year cycle, which is not a prime number, would be endangered every time it emerged.

  A second hypothesis reaches back to the ice ages. Under this idea, long cycles evolved so that cicadas could outlast cold spells. As different groups emerged together and hybridized, the species that stayed distinct were those with periods matching prime numbers.

  Synchronization itself may also pay off. Emerging all at once may make cicadas a less reliable meal and may overwhelm predators before serious losses occur. When the swarm does arrive, amphibians, fish, reptiles, mammals and birds change their foraging habits to profit from the glut.

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• 4. The Loudest Song

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  A single cicada can sing at up to 120 decibels, among the loudest sounds any insect makes. Only males produce it. A pair of tymbals, drum-like structures made of a rubbery protein called resilin, sits below each side of the front abdomen. Muscles buckle the tymbals, and when the muscles relax they snap back quickly, producing clicks.

  By vibrating the membranes rapidly, a cicada blends those clicks into apparently continuous notes. In many species the male abdomen is largely hollow and works as a sound box. Enlarged chambers derived from the breathing tubes amplify the sound further. The cicada also shapes its song by pointing its abdomen toward or away from its perch.

  Each species combines its clicks in its own pattern, so the song attracts only fitting mates. Entomologists treat these songs as unique to a species, and several resources exist for collecting and analysing them. Some cicadas add a quieter courtship song once a female has been drawn in. Males also use encounter calls, either in courtship or to keep personal space within a chorus, and many species have a broken, erratic distress call when seized.

  Both sexes have tympana, membranes that work like ears. Males disable their own tympana while calling, which protects their hearing. At close range, the song can cause permanent hearing loss in humans. Some small species sing at pitches too high for people to hear at all.

  Locating a singer is hard for a human listener. The pitch is nearly constant, the sound seems continuous, and cicadas sing in scattered groups. Not every cicada relies on tymbals. In the Chinese species Subpsaltria yangi, both males and females stridulate by rubbing their wings over ridges on the thorax. The hairy cicadas of the family Tettigarctidae have rudimentary tymbals in both sexes. They send vibrations through the tree they perch on instead of making airborne sound, and they are considered close to the original state of cicada communication.

  Timing matters too. Most cicadas call by day and sing most actively in the hottest hours, since they depend on outside heat to warm up. The South American species Fidicina rana lives where the average temperature is about 29 C, yet its tymbal muscles run significantly hotter while it sings. Kanakia gigas and Froggattoides typicus are known to call at night. Two Californian species, Okanagana pallidula and Okanagana vanduzeei, call from hollows at the base of a tree, below ground level. The burrow does not amplify or change their calls, and why they do it remains unclear, though it may help them avoid predators.

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• 5. Built For Heat And Rain

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  Above about 39 C, a desert cicada such as Diceroprocta apache does something unusual among insects. It sucks up extra sap and pushes the surplus water out through pores in its back plate, cooling itself the way sweat cools a mammal. This can lower its body temperature by some 5 C. The trick works only because the cicada feeds on water-rich xylem sap. A non-desert species, Magicicada tredecem, also cools itself this way, though less dramatically. Many other cicadas do the opposite and can raise their body temperature as much as 22 C above the air around them.

  The fore wing is covered in minute waxy cones, blunt spikes that make the surface superhydrophobic, or strongly water-repellent. Rain rolls across the wing and carries dirt away. In dry weather, dew condenses on the wing, and when droplets merge the cicada leaps several millimetres into the air, which cleans the wing again. Bacteria that land on the surface are not pushed off. Instead, the nanoscale spikes tear their membranes apart, making this the first-known biomaterial that can kill bacteria.

  The jets of fluid that cicadas expel travel at up to 3 meters per second. That makes them the fastest of any animal assessed, faster than those of elephants and horses. The reason is a diet of enormous volumes of xylem sap.

  Three small eyes called ocelli sit in a triangle on top of the head, between the two large compound eyes set wide apart. These ocelli distinguish cicadas from other members of the order Hemiptera. A large, nose-like structure called the postclypeus makes up most of the front of the head and holds the pumping muscles. Females end in a large, saw-edged ovipositor for cutting into bark.

  Unlike their relatives the leafhoppers and froghoppers, cicadas are feeble jumpers, and nymphs cannot jump at all. Adults walk poorly and fly whenever the distance exceeds a few centimetres. The largest species, the empress cicada Megapomponia imperatoria, has a head and body about 7 cm long and a wingspan of 18-20 cm.

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• 6. Hunters And Defenses

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  In northern Japan, brown bears dig up the ground in summer to reach cicada nymphs in their final stage. Birds, mammals, bats, wasps, mantises, spiders and robber flies also eat cicadas. Newly hatched nymphs may be eaten by ants, and moles hunt nymphs underground.

  The Australian cicada killer wasp, Exeirus lateritius, stings and stuns cicadas high in the trees so that they fall to the ground. The wasp then mounts its victim and pushes it along with its hind legs, sometimes over 100 m. At its burrow, it shoves the numb cicada onto one of many shelves in a catacomb of food for the grub that hatches from its egg.

  Some predators exploit the song itself. A katydid predator in Australia imitates the timed click replies of receptive females, and singing males of many species come to it. The sarcophagid fly Emblemasoma also hunts cicadas by sound. Singing males respond by softening their song so that a listener is drawn to louder neighbours, or by falling silent as a predator approaches. A loud chorus has been claimed to repel predators, but observations of how predators actually respond contradict the claim.

  The fungus Massospora cicadina attacks adults of periodical cicadas, and its spores lie dormant in the soil between outbreaks. It can dose cicadas with psilocybin, the psychedelic compound in magic mushrooms, along with cathinone, an alkaloid similar to amphetamines. The chemicals alter behaviour and drive males to attempt mating, even with other males. This is thought to help the fungus, since more infected carriers spread more spores. Fungi of the genera Ophiocordyceps and Isaria attack nymphs instead.

  Plants fight back as well. Resinous conifers such as pine do not allow the eggs of Magicicada to hatch, because the resin seals up the egg cavities.

  Most cicadas rely on disguise. Colored like tree bark and marked with outline-breaking patterns, they press their partly transparent wings close to the surface and become hard to see. Some species play dead when threatened. Hemisciera maculipennis flashes bright colors on its hind wings to startle a predator and buy time to escape. In Malaysia, Huechys sanguinea borrows the red and black colors that warn of toxicity in other animals and flies boldly in full view.

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• 7. Deep Time Wide Range

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  In 1873, a fossil fore wing from the Taynton Limestone Formation of Oxfordshire, England, was described as a butterfly. It was later recognised as a cicada-like form and renamed Palaeontina oolitica. It belongs to the Palaeontinidae, the so-called giant cicadas, which are only distantly related to true cicadas. They lived in the Jurassic and Lower Cretaceous of Eurasia and South America.

  By the Middle Jurassic, about 165 million years ago, fossils related to both living cicada families already existed, so the two lineages had split earlier. Early relatives of the Cicadidae preserved in mid-Cretaceous Burmese amber from Myanmar were probably silent or only made quiet sounds. The oldest unambiguously identified modern cicadid is Davispia bearcreekensis, from the Paleocene, around 56-59 million years ago.

  Today the two families are very unequal. The Tettigarctidae include only two living species, one in southern Australia and one in Tasmania. The Cicadidae are found on every continent except Antarctica, in essentially any habitat with deciduous trees, and most live in the tropics. Cicadas as a group are the sister of the froghoppers, the Cercopoidea.

  Australian cicadas carry nicknames such as cherry nose, brown baker, red eye, greengrocer, yellow Monday, whisky drinker, double drummer and black prince. The greengrocer, Cyclochila australasiae, is among the loudest insects in the world. Australian species live on tropical islands, on cold beaches around Tasmania, in deserts, in alpine areas of New South Wales and Victoria, and in cities including Sydney, Melbourne and Brisbane.

  New Zealand has more than 40 species from five genera, all endemic to New Zealand and its surrounding islands, including the Kermadec Islands and the Chatham Islands. Their closest relatives live in New Caledonia and Australia. Elsewhere, South Africa has around 150 species, America north of Mexico has over 170, Latin America has at least 800, and Southeast Asia and the Western Pacific have over 200. Many genera are confined to a single region, and that high endemism has helped scientists study the biogeography of island groups such as Indonesia.

  About 100 species occur in the Palaearctic. Europe has only a few, and England once knew a single species, the New Forest cicada, Cicadetta montana, which also lives on the continent. In North America, the annual cicadas of the genera Neotibicen, Megatibicen and Hadoa are called jarflies or dog-day cicadas because they emerge in late July and August. Many species still await formal description, and many well-known ones have not yet had their songs characterized with modern acoustic tools.

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• 8. Cicadas And People

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  Diaochan, a character in the 14th-century Chinese novel Romance of the Three Kingdoms, took her name partly from cicada-shaped jade decorations that adorned the hats of high officials. Cicadas appear as motifs in decorative art from the Chinese Shang dynasty (1766-1122 BCE). In Chinese tradition the cicada symbolises rebirth and immortality. The phrase "to shed the golden cicada skin" names a stratagem of leaving a decoy behind to fool enemies, and in Journey to the West the Priest of Tang is called the Golden Cicada.

  Homer's Iliad features cicadas, and Aristotle describes them in his History of Animals. Pliny the Elder covers them in his Natural History. Hesiod wrote in Works and Days: "when the Skolymus flowers, and the tuneful Tettix sitting on his tree in the weary summer season pours forth from under his wings his shrill song". The Greeks used a cicada sitting on a harp as an emblem of music.

  The Homeric Hymn to Aphrodite tells of the goddess Eos, who asked Zeus to let her lover Tithonus live forever. She forgot to ask that he also stay young, so he grew old without end. He shrank until he turned into the first cicada.

  In La Fontaine's fables, the first story, "La Cigale et la Fourmi", is based on one of Aesop's fables. The cicada sings through the summer while the ant stores food, and the cicada is left hungry when winter turns bitter. In France, the cicada stands for the folklore of Provence and the Mediterranean cities.

  In Japan, many people feel summer has not begun until the first cicada songs are heard. According to Lafcadio Hearn, the song of Meimuna opalifera, called tsuku-tsuku boshi, signals the end of summer. In The Tale of Genji, the title character likens one of his love interests to a cicada for the way she delicately sheds her robe. Cicadas are a frequent subject of haiku, where, depending on type, they can indicate spring, summer or autumn. In the Philippines, Kapampangan mythology says the goddess of dusk, Sisilim, is greeted by the sounds and sight of cicadas.

  Modern artists keep returning to the insect. Shaun Tan's illustrated book Cicada tells of a hardworking but underappreciated cicada in an office. Branden Jacobs-Jenkins's play Appropriate calls for the sound of mating cicadas throughout. María Elena Walsh wrote the protest song "Como La Cigarra", in which the cicada stands for survival and defiance against death, and Mercedes Sosa recorded it. Raymundo Perez Soto wrote the mariachi song "La Cigarra", which romanticises a creature that sings until it dies. The Brazilian artist Lenine built the track "Malvadeza", from the album Chao, on cicada sound. On her 2021 album Solar Power, New Zealand artist Lorde used cicada song as an emblem of the New Zealand summer.

  Cicadas were eaten in Ancient Greece and are eaten today in China, Myanmar, Malaysia, central Africa, parts of Mexico and North America, and the Balochistan region of Pakistan, especially in Ziarat. In China, people eat both adults and, more often, nymphs. Females are prized for being meatier. The 17-year Onondaga Brood of Magicicada is culturally important to the Onondaga people and a particular delicacy. Cicada shells are used in traditional Chinese medicine, with claims of anti-convulsive, sedative and fever-lowering effects, and the lightweight shells can serve as hair or clothing accessories.

  Cicadas do not bite or sting, though one may mistake a person's arm for a plant limb and try to feed, causing slight discomfort. They are not major agricultural pests. In outbreak years, though, females laying eggs in the shoots can overwhelm trees, so small trees may wilt and larger ones lose small branches. Some species have turned from wild grasses to sugarcane, and in a few isolated cases females have laid eggs in date palms, grape vines, citrus trees, asparagus and cotton.

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