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.