Cicadas are awakening and emerging from the ground in Nebraska, Texas, Missouri, Iowa, and Oklahoma, following 17 years of sleep. Affected areas in these states could experience a noisy invasion of insects in late May and early June.

These insects are only infrequently seen emerging from their underground hiding places. The most common sights are rather the exoskeletons of the creatures — covering homes, gardens and yards after the passage of a swarm. When millions of the insects pass through a region, the percussive sounds can be difficult to tune out.

"The sound, I won't say it's deafening, but it's incredibly loud. You couldn't have a normal conversation, they're so loud," said Leon Higley from the School of Natural Resources at the University of Nebraska-Lincoln, after witnessing one of the events in Kentucky back in 1981.

Cicadas live in 12 main broods across the United States. Last seen in 1998, the currently emerging insects are known as the Kansan brood, or Brood IV. Some species of the insect take flight every year, while others emerge in cycles of three, seven, 13 or 17 years. These are strangely all prime numbers, and this does not seem to be a coincidence.

"The theory is that the reason they have life cycles that correspond with prime numbers is that predators have difficulty in getting in synch with their life cycles. They are avoiding something, and they can do it by this long life cycle," Higley said.

The exact time when the coming insect invasion will peak is difficult to predict, as it depends on the arrival of warmer temperatures and more abundant foliage.

Cicadas live entirely on juices extracted from trees, and don't bite or sting people. That distinctive racket come from males cicadas attempting to attract a mate. Their wings flap open and closed over cavities in their bodies, which amplify the sound like the wooden shell of a drum.

After mating, females lay up to 600 eggs at one time into tree branches, which hatch into insects that eat their way down to the roots of their host. There, they eat all they can, before molting and taking to the skies as their parents did before them. The entire process takes around three weeks to complete. Biologists state that the process of cicada reproduction can damage trees affected by invasions of the insects.

Cicadas are commonly confused with locusts, but those insects are actually large flying grasshoppers.