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Brood II: After 17 years, billions of eastern US cicadas rise again

After 17 years out of sight and under foot, billions of noisy, bulge-eyed Brood II cicadas are crawling out of the ground in the eastern US to mate, hatch offspring, and start the cycle anew.

By / May 7, 2013

Any day now, cicadas with bulging red eyes like this one, seen in 2003, will creep out of the ground after 17 years and overrun the East Coast with the awesome power of numbers. Big numbers. Billions. Maybe even a trillion. For a few buggy weeks, residents from North Carolina to Connecticut will be outnumbered by 600 to 1. Maybe more.

Chris Simon / University of Connecticut / AP / File

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If you live on the East Coast and enjoy a walk in the woods or a tree-filled park, for the past 17 years you almost certainly have been walking over buried, juvenile cicadas, one of the most remarkable – and annoying – insects on the planet.

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Now, it's their turn on stage. Between now and June in the eastern US, the insects are emerging from underground in a kind of Rolling Thunder Review from south to north as soils grow toasty enough to signal break-out time.

Over four to six weeks, males will sing to attract females. Pairs will hook up. Billions of tiny offspring will hatch from eggs the females deposit in trees. The tiny offspring will plummet to the ground and burrow back into the soil weeks after their parents – every winged, bulge-eyed one of them that hasn't been eaten by a bird, raccoon, or chipmunk – depart this vale of tears.

While most of the current sightings are east of the Appalachian Mountains, the bugs are appearing in the southern Plains as well, from Texas north to Nebraska, although these may be stragglers from a different brood. (Broods are identified by region, cycle length of 13 or 17 years, and years in which they reappear. The bugs appearing in the eastern US belong to Brood II.)

These “periodic” cicadas pose no serious threat to humans, although they can sting a bit if they mistake you for a tree, entomologists say.

Estimates put underground, periodic cicada populations at from tens of thousands to as many as 1.5 million individuals per acre. And they boast the longest life span of any insect, according to researchers Walter Koenig at Cornell University and Andrew Liebhold, with the US Forest Service's Northeastern Research Station in Morgantown, W. Va.

While the bugs have prompted people to alter wedding dates and forestall planting new, young trees until after the cicadas' festivities end, they play a number of roles in forest ecology, researchers say.

“There still are a lot of mysteries about how periodical cicadas interact in forest ecosystems,” says Dr. Liebhold, but one clear role seems be as a source of nutrients for forest soils.

Once the adults die and fall out of the trees and shrubs they occupied, they decompose. That tends to trap nutrients close to the roots, where the food is less vulnerable to leaching from the soil. This fertilizer feeds the trees and shrubs directly. It also feeds the next generation of cicadas indirectly because the nymphs that burrowed into the ground feed off fluids that move through small roots.

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