As billions of cicadas await their cue to erupt from their 17-year home deep within the earth, Theresa Flanagan and her two children set their sights Saturday on convincing dad that there's nothing to fear.

A city slicker until he moved to Garrison six years ago, Flanagan's husband Joseph fears the invasion will be a nuisance, forcing him to store their cars in the garage all summer, she said. Their neighbor worries plants and gardens will be destroyed.

But, as Flanagan and her two children, Olivia, 8, and Liam, 6, learned from educators at the Hudson Highlands Nature Museum on Saturday, the red-eyed bugs are harmless, if a bit loud, and vital to the ecosystem.

"We came here to learn about the cicadas and prove to daddy that there is nothing to worry about," Theresa Flanagan said. The Flanagans were among about two dozen Hudson Valley families at the Cornwall nature museum.

As soon as the soil temperature hits 64 degrees for two consecutive days, mature cicada nymphs will tunnel out from the burrows where they have lived since 1996, climb trees and begin several weeks of mating calls that can reach up to 100 decibels -- about as loud as a motorcycle. They will mate, lay eggs and die, while their offspring crawl underground, renewing the 17-year cycle.

Led by Pam Golben, director of the museum's wildlife center and museum educator Megan Hoffman, the group explored the nearby forest in search of the inch-long bugs. While they came up empty -- the soil temperature is only 50 degrees -- they found dozens of little holes from which the cicadas will soon emerge.

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Olivia has already seen her first cicada. While building a "secret garden" with her best friend, the 8-year-old spotted tunnels, inserted her finger -- and out popped a cicada. She plucked it up from the earth, studying it for a minute, and then returned it to its home.

"They look interesting," she said. "I didn't know that any kind of bug would live 17 years."

When cicadas last erupted in the Northeast 17 years ago, Susie Moyik was 23, living in Chicago and employed at her very first job. Now 40, Moyik lives in Cornwall, has a 4-year-old son and a 16-year-old stepson -- and she's never seen a cicada.

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But she has seen their nickel-sized tunnels with her youngest son, Christian, who she brought to the museum Saturday. During the next cicada invasion, Christian will be 21.

"Are they going to realize any of the changes in the environment?" Moyik wondered. "It's weird to think how different life will be when they come back."