Sounds of Summer: The Charming Cicada Cacophony

The central-eastern chunk of North America has a very distinctive background noise for a substantial chunk of the year.  While this sound is not totally distinctive to the United States and Canada east of the Mississippi River, the one here has special properties.  I speak, of course, of the buzz of the cicadas.  Erroneously called “locusts” because of their size and song, these insects have far more going on than meets the eye.

I remember my first encounter with one very well.  I added the placid, unknown behemoth to one of several plastic insect habitats that were my favorite toys during the warmer New Jersey months, alongside some houseflies and beetles I’d caught earlier that day.  I had to go inside, probably for food, and we soon heard a noise that we thought was some sort of chainsaw or motorcycle, but coming from the backyard.  Alarmed and confused, my parents and I went outside and quickly localized the sound to the insect dome, and to the huge bug inside.  The heat had given it a bit more energy and an amplifier, which it naturally devoted to its mating call.  I let the beast go shortly thereafter.  Cicadas would have a special place in my heart after that, combining teeming masses with an alien countenance.

Cicadas are easily the largest insects most city-dwellers in North America encounter, comparable in size to the largest local grasshoppers and far heavier than native roaches or butterflies.  Many people fear them on that basis alone, but the creatures are quite harmless to humans.  As nymphs, cicadas feed on xylem fluid from tree roots; as adults, they drink the same from stems and branches.  Reportedly, a cicada left unmolested on a person’s skin for hours might confuse them for a branch and try to insert its proboscis, which can be painful.  That is, to get a cicada to hurt you, you have to pretend to be a tree.

Cicadas do make nuisances of themselves in other ways.  They are drawn to loud noises, such as lawnmowers, and sometimes swarm people who operate such devices during their mating season.  As large insect herbivores, they can also damage garden plants, particularly ornamental trees grown somewhat outside their natural range and therefore growing less strongly than native flora.  While feeding, they often take in too much fluid and have to excrete some of it, which they also do when disturbed, adding a sticky, sugary “cicada rain” to the weather forecast of public parks and forests.  And, of course, there’s the noise.

Large 17-year cicada on a person's arm.  The cicada is black with red eyes and transparent wings with yellow-brown veins.
by New Jersey Star Ledger staff
Cicada song has a very different instrument than the songs of other insects.  Grasshoppers produce sound by rubbing their hind legs against their abdomens or forewings, using specialized hardened surfaces on both structures.  Crickets work similarly, but rub their forewings against each other.  Cicada song comes from the vibration of two abdominal organs called tymbals.  To sing, male cicadas rapidly contract and relax their abdominal muscles, which otherwise serve to control the shape and thickness of the abdomen, to rapidly click these tymbals back and forth.  Each cycle has two discrete clicks, much as a heart contracts and relaxes, but cicadas vibrate their tymbals so quickly that their song appears to humans as a continuous tone.  The air spaces that comprise the cicada’s respiratory system amplify the sound, and the cicada can further modulate its song by holding its abdomen closer or farther away from the surface on which it rests.  Singing cicadas are extremely responsive to their environment, and have separate songs to draw prospective mates, to woo female cicadas that have already responded to the calling song, to maintain small territories in calling groups, and to surprise creatures that disturb or grasp them.

And cicadas are loud.  Larger species can produce sound with an intensity of 100 or 120 decibels, comparable to a gasoline chainsaw, jackhammer, or vuvuzela one meter away and very close to the threshold of instantaneous hearing loss for humans.  Singing cicadas actually turn off their own ears to protect their ability to hear.  Fortunately, cicadas typically sing in trees and sound intensity decreases with the square of the distance from the source, so cicada mating swarms do not usually cause plagues of deafness.

A bush covered in freshly emerged, light brown cicada nymphs preparing to molt into adults.
From Wikimedia Commons.  Photo by Arthur D. Guilani.
Also, those swarms are not omnipresent.  Cicadas are additionally famous for their extremely long and bizarrely synchronized life cycles.  Some species, called “annual” cicadas, have emergences every year, though individuals take several years to reach maturity.  The best-known cicadas take 13 and 17 yearsto mature, emerging in massive recurring broods that entomologists both professional and amateur have learned to track and anticipate.  Cicadas on a particular cycle in a given area tend to emerge in the same year, so most years have small numbers of cicadas (from annual species, from the edges of nearby broods on offset cycles, or by chance), punctuated with years of huge swarms.  The long prime-number life cycles have been the subject of much speculation and theorizing, and it remains unclear what selection pressures could potentially lead in that direction.  Prime-number life cycles are unlikely to regularly coincide with shorter- or longer-period population cycles of other species, which may enable the cicadas to avoid timing their emergences with population booms among their many predators.  Some suggest that such long life cycles may protect the periodic cicadas from parasitoid wasps, which tend to be species-specific and therefore could not survive on such rare hosts.  Periodical cicadas have no parasitoids, whereas their annual kin do, bolstering this hypothesis.

Several cooked cicadas on a skewer, near a pile of similar cicada-laden skewers
As large, noisy, slow insects that appear predictably in large numbers, it is no surprise that cicadas feature in the cuisines of many parts of the world.  The indigenous peoples of North America roast them in fires, North Chinese cuisine features them deep-fried, and eaters as far-flung as Greece and indigenous Australia find recipes for these curious insects.  Eating cicadas is such a well-developed practice that enterprising entomophages as well-known as Aristotle have suggestions about which molts and genders are tastiest.  (Apparently it’s freshly-emerged cicadas, before their shells harden, and females full of eggs.)  Modern recipes add them to banana bread, marinate them in Worcestershire sauce, or stir-fry them with coriander and water chestnuts.  Cicadas are unlikely to be farmed anytime soon, given the nature of their life cycles, so such recipes will remain a novelty for Westerners and a fact of life for people who rely on wild seasonal food for sustenance.

Snack tray from Provence in the shape of a cicada, with additional decorative olive motifs.

Cicadas also feature prominently in folklore and myth from around the world.  In Japan, cicadas are symbols of seasonal change, as the islands feature sequential emergences of different species; and of deception, as animals that leave curiously intact shells behind them as they emerge.    Japanese and Chinese folklore also holds the creatures as symbols of reincarnation, for similar reasons.  In France, cicadas are symbolic of Provençal culture, used as a visual shorthand or decorative motif throughout southern France in particular.  Provençal lore holds that the cicadas are godly messengers sent to encourage the peasantry to stop lounging about and get to work.  In much of Europe, they are instead a symbol of insouciance or merrymaking, as animals that spend virtually all of their time “sleeping” underground, singing, or copulating.  Several Greek and Italian stories feature humans whose talent for music led to the gods transforming them into cicadas, that they might know recurring eternal life as creatures that always sing.  A particularly dark twist on this story is the Greek myth of Tithonus.  Husband to Eos, goddess of the dawn, he was granted immortality but not eternal youth.  As he grew infirm and crippled, Eos transformed him into the cicada, the returning, ageless singer.  The Greeks were aware that only male cicadas sing, leading the Greek poet Xenophon to bitterly muse, “Blessed are the cicadas, for they have voiceless wives.”  And, of course, there is Aesop’s famous fable of the lazy, musical grasshopper and the wise, industrious ant, which was originally the cicada and the ant, before the curious use of the term “locust” for cicadas led to the story taking its current form.

(I rather prefer this version of the story, myself.)
And one of them made it into the Beast Wars roster as Cicadacon:
A posed action figure of a cicada that transforms into a winged robot holding two wing-shaped swords.
These mythic, season-defining, weird, wonderful cousins ofthe deliriously beautiful leafhoppers and fulgorids deserve far more love and far less terror than they currently receive, and it is my hope that understanding this significance will help other people see their charms.

Especially in Malaysia, where they look like this:
A Malaysian Tacua speciosa cicada the size of the hand of the person holding it.  The cicada is black with yellow and brown stripes and black-brown wings.
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2 comments

  1. One thing you learn when traveling is that cicadas have different songs depending where you are. The North American's cicada is a long continuous whine while the European is a repeati motif. (I might be a bit biased)

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  2. I'll believe it. In places where more than one species breeds in the same season, their calls differ enough for them to know the difference, so the differences across oceans are almost certainly greater.

    Like

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