Trillions of cicadas are set to emerge from the ground this spring in a rare double-brood event that hasn’t occurred in over 200 years. Two broods, Brood XIX and Brood XIII, will emerge in over a dozen states, with the two likely overlapping in Iowa and Illinois. The emergence of these cicadas is triggered when the soil 8 inches underground reaches 64 degrees, often following a warm rain, and is expected to last from mid-May through late June.
The last time these two broods emerged was in 1803, and the next predicted double-emergence is not expected until 2245. Cicadas have the longest life cycle of any insect, waiting 13 or 17 years to emerge. Once above ground, female cicadas lay eggs in trees, which drop to the ground and burrow, waiting for years to emerge, depending on their brood. The adults cicadas will mate, lay millions of eggs, and die in about five weeks.
Cicadas are not harmful to humans, pets, household gardens, or crops, according to the EPA. Despite their overwhelming numbers, they can provide some environmental benefits, such as serving as a valuable food source for birds or predators, aerating lawns, improving water filtration, and adding nutrients to the soil as they decompose.