By Dan Klepal
Enquirer staff writer

Brood X is heading back to the underground.

The 17-year periodical cicada known as Brood X that invaded Greater Cincinnati, along with other Midwestern and mid-Atlantic states, this summer are dead and gone. But the next generation of Brood Xers are about to hatch from their tree nests, drop to the ground and tunnel under the surface as fast as their six little legs can dig.

Dr. Gene Kritsky, a cicada researcher and biology professor at the College of Mount St. Joseph, said the baby cicadas - called nymphs - could start emerging next week. Cicada eggs, laid in branches, take six to eight weeks to hatch.

"Ants and spiders go after them as soon as they start dropping, so they get below ground as fast as possible," Kritsky said.

Once underground, the nymphs feed on moisture in plant roots. They also build cells to live in, using excess moisture to cement walls of their cells together. The nymphs will remain under ground until their next emergence, in 2021.

Kritsky said the newly hatched nymphs are tiny, less than 2 millimeters long and are difficult to see. They will grow to about one inch during their long stay underground.

"You can see them if the sun is behind the tree, so you have a little back lighting," Kritsky said. "It will look like sparkly confetti."

More than 5 billion cicadas invaded Greater Cincinnati this summer. Females that lived long enough each produced between 400 and 600 eggs.

Mike Raupp, a University of Maryland entomologist who has monitored this year's cicadas, said the mortality rate for nymphs is around 90 percent. That's why females produce so many eggs.

"For real cicada people, it's not over yet," Kritsky said.

The Associated Press contributed to this article.

E-mail dklepal@enquirer.com