The invasion began about a month ago.

The invaders, lurking underground since 1998, tunneled through the earth and up onto bushes, tree trunks, maybe your house.

They emerged from their papery exoskeletons, leaving the brown husks behind, and then, by the untold millions, took to the air.

The 13-year cicadas - Brood XIX - have been creating an unearthly racket ever since.

The males produce that eerie flying-saucer sound.

The big bugs are a little scary, with their blank red eyes, but they're harmless; they don't bite, and they don't eat crops or your azaleas.

Their current reign is all but over. The females have been laying their eggs. The nymphs will burrow into the ground to feed on tree roots until their time comes.

And Brood XIX, having fulfilled its destiny and mated, is dying.

Soon - perhaps this week - the woods will be silent again, until 2024, when the next generation will make its way to the surface.

"All this biomass coming up out of the ground, altering every body's lives for about a month then disappearing for 13 years, its all pretty awe inspiring," said Dr. Clyde Sorenson, professor of entomology at N.C. State University.

Brood XIX, also called The Great Southern Brood, made its last appearance in 1998, coinciding with the 17-year-cycle cicada Brood IV.

The broods didn't overlap geographically, so together they covered one-quarter of the country - from Maryland south to Georgia, and west to Texas - offering the largest geographic covering of cicadas, according to Sorenson.

That won't happen again until 2219.

Cicadas inhabit every continent except Antarctica. But the only place in the world where they sync en mass is the Eastern United States, said Dave Stephan, an entomologist at N.C. State University.

Sorenson said that the emergence of Brood XIX has become admired in the modern era. In years past, when less information was available about insects, people feared the broods, which were thought to be a cloud of menacing locusts.

Noise complaints

The broods' sounds still draw curiosity. Sorenson said people often complain about birdsong being drowned out by the noise of the cicadas' mating calls.

According to Sorenson, people sometimes call their power companies wondering whether there is a problem mistaking the hum of the cicadas for some mechanical malfunction.

But before long, that won't be a problem.

"We don't have to think about them for another 13 years," Stephan said.

matthew.caulder@newsobserver.com or 919-829-4889