Trillions of cicadas in the eastern US are waking from a 17-year slumber in what scientists expect to be the largest insect emergence on Earth.
The last cicada swarm in the United States emerged in 1987
The winged insects, which have been living underground and feeding on tree roots, will engage in a frenetic mating cycle before dying en masse in June.
The bugs are harmless, but their mating call is very noisy.
They are expected to swarm over 14 eastern states including Georgia, Indiana, Kentucky, New York and Ohio.
There are more than a dozen separate broods of 17-year cicadas, along with several 13-year varieties.
Periodical cicadas are only found in the eastern United States.
University of Indiana cicada expert Keith Clay says he expects this year's brood, Brood X, to be the largest.
The insects can reach densities of up to 3,000kg/hectare, he told a news conference at the National Science Foundation, Reuters reported.
17-YEAR CICADA LIFECYCLE
1. Female lays eggs and dies soon after. Eggs hatch.
2. Bugs or 'nymphs' drop to the ground
3. Nymphs live underground feeding on tree roots
4. After 17 years, nymphs tunnel to surface, crawl up trees and shed skins to become adults
5. Adults mate during May and June of 17th year
Along with other scientists, he plans to study the mass coming-out in a bid to discover how the insects developed their unique lifecycle.
The adult males initiate the mating cycle with a long, loud buzzing noise which attracts females. Different species have different mating calls.
One is said to sound like a flying saucer from a 1950s science fiction film, while another is said to make a sizzling noise.
After the adult insects have mated, the females cut slits into tree branches, where they deposit up to 600 eggs. The adults then die.
"They rot very quickly and they smell really bad for a few days, and will disappear on their own," Professor Clay said.
The eggs hatch in a few weeks, and the young cicadas burrow into the ground.
Homeowners have been warned to use netting to protect young trees and shrubs.
Cicadas are often described as stupid for their inability to defend themselves - they are easy prey for birds and dogs.
"We prefer the term 'predator foolhardy'," University of Connecticut biologist Christine Simon told Reuters.
It makes things easier for people who like to eat them - young cicadas are said to taste like canned asparagus.
But curious diners should take advantage of the glut as the next monster swarm is due in 2021.