Billions of cicadas to swarm East Coast this spring (VIDEO)

Billions of cicadas are set to swarm the East Coast this spring affter nearly two decades underground.

The noisy, flying insects are forecast to descend upon cities, towns and villages from North Carolina to New England in an event that happens just once every 17 years.

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Called Brood II cicadas, they will emerge for the first time since 1996, and cover any East Coast area warmer than 64 degrees from about mid-April to late May, the New York Daily News reported.

Experts assure they're harlmess to trees and humans.

But they're very noisy as males make their distinctive call for mates and will be harder to ignore.

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"The specific thing about these 17-year cicadas is they are going to be a very dark-colored body," Craig Gibbs, an entomologist at the Wildlife Conservation Society's Queens Zoo, told CBS News. "They have really bright red eyes, and they also have bright red wing veins."

Both adults will die shortly after mating. Their eggs will hatch this summer and their offspring will burrow into the ground for another 17-year incubation period.

While underground, the bugs feed off fluid that gathers near the roots of plants.