I was taking my dog for a walk into the normally peaceful woods of Montrose Park a few days ago, when I suddenly realised I was being practically deafened by a kind of white noise I had not heard before. It was a thunderous roar, rather like that of the Niagara Falls. People have measured it with noise machines and found the thunder to measure roughly 90 decibels, worse than rush-hour traffic. It was, I have to say, a peculiarly magical moment, that which only nature can bring.
What I was hearing was the mating call of the male Magicicada Brood X cicada, a flying insect one and a half inches long that appears once every 17 years. The time before last (in 1970), Bob Dylan wrote a song about the phenomenon. Some different families of the cicada emerge every 13 years, but periodically emerging cicada such as these are known only in the United States. They are peculiarly beautiful creatures, with protruding reddish pink eyes and infinitely membranous wings tinged with yellow and with what appears to be a distinct letter on the edge of the wings. Despite their prominent eyes they are practically blind, which explains why the pavements here are littered with dead cicadas that have met with flying accidents.
They appear only in 14 states (plus DC) on the eastern side of the country, but in huge numbers: as many as 1.5 million per acre, according to entomologists. They have short lives, emerging to mate, lay eggs and then die within a month.
The sound I heard was the male's mating call, made by rubbing together ribbed membranes on their bellies known as tymbals. The male cicada then tenses a muscle attached to each tymbal, distorting its body like a dented Coca-Cola can. That produces a buckling pulse of air which is pressurised into the insect's abdomen. Flighty female cicadas then waggle their wings to signal readiness and the happy couple mate for the first and last time. The exhausted male quickly dies, followed by the female after she has laid her eggs. Larvae, which look like grains of rice, then begin hatching on the tree sap and head speedily for below ground.
Why 17 years? Nobody has a firm answer: it is just one of nature's mysteries. The most likely explanation is that they have evolved the cycle to avoid predators. Seventeen years after hatching, the larvae - known by now as "nymphs" - tunnel up out of the ground on to the surface, crawl up trees and shed their skins to become the adults that fly around in billions, possibly even in trillions.
We are in the middle of a cicada craze here. The newspapers are full of cicada stories, including ones where the creatures have supposedly caused accidents by flying into windscreens and startling drivers. There are cicada-eating crazes, with one cicada expert saying he prefers them covered in chocolate; dead, they are harmless to eat (they have a "nutty" flavour, someone told me).
Schoolchildren are predictably fascinated: at one school I know, children smuggled a cicada in to fly around the classroom - only for the insouciant biology teacher to grab hold of it and pop it into his mouth before crunching and swallowing it.
This being America, the outbreak has spawned websites such as www.cicadamania.com, which sells souvenir T-shirts and postcards; I even have a cicada cookie, which I have not yet eaten. Much interest surrounds a rarer type of cicada with blue eyes, which is cheerfully advertised on eBay for $12.50.
The creatures are harmless to man and do not bite or sting, though they can urinate en masse on people; the only other downside is that they munch on crops and can harm young deciduous trees such as maples, oaks and fruit trees.
What seems to be an identifying W or a P appears on the cicadas' wings: according to urban legend, this means there is either war or peace ahead. I have, I am afraid, seen many more distinct W's than P's.
I remember once watching young turtles emerge from their eggs buried weeks earlier under the sand by a female turtle in Florida: the tiny turtles began a life-or-death rush to the sea, with predator birds flying overhead and swooping on the unlucky ones. Some other unfortunates began to flee from the sea in the confusion. It was one of nature's processes that I feel privileged to have seen; in a strange sort of way, I feel equally blessed to have witnessed this cicada phenomenon.
Blissfully unaware of the troubled world above them, the larvae now busily burying themselves under trees will not emerge until 2021. How, I wonder, will the world have changed by then? How will history have judged the likes of George W Bush, Donald Rumsfeld and Condoleezza Rice? Will Hillary Clinton or some other woman have made it to the White House? We will all know, God willing, in 17 years' time when, like clockwork, the mysterious Magicicada Brood X next emerges.