College Park, Md. ? Their droning love songs have faded, the skies are free of their tumbling flights and the carcasses that littered sidewalks have washed away.

The Brood X cicadas, vintage 2004, are gone.

But in the trees of several mid-Atlantic and Midwest states, the next generation is just beginning its 17-year life. Within the next few weeks, billions of eggs deposited in tree branches will hatch and rain down tiny white nymphs no bigger than sesame seeds with beady red eyes.

They will burrow through the dirt to tree roots and won’t emerge as adults until 2021.

“We’re sitting on the nest right now,” said Mike Raupp, a University of Maryland entomologist who has closely monitored this year’s cicadas.

Most people won’t notice the nymphs’ dash to safety since they are so small, said Gene Kritsky, a biology professor at the College of Mount St. Joseph in Cincinnati. But if seen in the right light, they look like small sparkles raining out of trees.

Over the past two months, billions of the Brood X cicadas inundated sections of the mid-Atlantic from New Jersey to Virginia, portions of the south such as Tennessee, and parts of Ohio and Indiana. Hordes tunneled up from their resting spots below trees, shed their skins and took flight. Males belted out mating calls at decibel levels that created an ever-present din.

But by mid-June, they began to die out. As their last act, females ready to lay eggs sought the tips of woody tree branches where each gouged dozens of small slits in the wood and deposited about 600 eggs apiece.

For the nymphs that emerge from their tree-tip nests, the world is a dangerous place. As they plunge to the ground, the nymphs are prime targets for predators such as bugs and mites. If the ground is too hard, they can’t burrow to the tree roots. In the first two years, mortality for nymphs is around 90 percent, Raupp said.

Red-eyed cicadas rest on a leaf in Annandale, Va. As these insects die off, another generation is just beginning its 17-year life cycle; they will emerge as adults in 2021.

For cicada buffs and scientists like Kritsky, who is drawing maps of the range of Brood X cicadas in Ohio and Indiana, the scientific work is still not done.

Raupp said he learned several things from this year’s crop of cicadas. They can fly up to 1,000 feet, he said, meaning they can move fairly far to colonize areas that previously didn’t have cicadas, such as new housing developments built in what were once fields.

He has also had reports of females laying eggs in some strange places: asparagus plants, goldenrod stalks and other herbaceous plants.