After a 17-year nap, trillions of red-eyed insects are crawling their way above ground in 14 US states and the nation's capital.
Loudmouthed and ugly, the cicadas will fly clumsily into pets, bushes and unwitting pedestrians as they engage in a frenetic mating ritual that lasts well into next month.
Then they'll disappear for another 17 years.
Keith Clay, a biologist and cicada researcher at Indiana University in Bloomington, said the appearance of cicadas is "an amazing biological phenomenon" that nonetheless produces a "yuck factor" for some people.
"They're not scared but see them as disgusting," he said.
The 4cm-long black bugs buzz around but are basically harmless. They don't bite and they don't sting. They live above ground as adults for about two-and-a-half weeks to reproduce as much as they can before dying.
The adult males begin the mating ritual with a long buzzing sound that attracts the females. The chorus from one colony's male insects is so loud that the insects can drown out outdoor wedding events, graduation ceremonies and golf tournaments, researchers say.
Scientists say this year's batch offers researchers a rare opportunity to study the insect's impact on the nation's forests. Recent studies indicate cicadas are growing in numbers due in part to deforestation.
Cicadas tend to thrive in sunlit forest edges, which often provide the warmer weather and younger trees most ideal for them to lay their young. That's because younger tree roots can sustain the 17-year feeding cycle of nymphic cicadas until they mature.
Found only in the US east of the Great Plains, the periodical cicadas burrow into the ground after hatching, some digging as far as 2.4m under.
After 17 years, they emerge and climb trees and shrubs, where they shed their crunchy skins and harden into maturity.
Once the bugs mate, the females cut slits into tree branches, where they deposit 400 to 600 eggs. The adults quickly die, but the eggs hatch in a few weeks. The young cicadas dig into the ground and won't emerge until 2021.
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