Why Does Brood X Happen?

A combination of suitable soil temperature and weather has prompted billions of cicadas, known as Brood X, to begin swarming large parts of the eastern United States. The insects last emerged in 2004, and although their loud mating calls can be distracting, they are not directly harmful to people.

What is the point of Brood X cicada?

Cicadas are mostly beneficial. They prune mature trees, aerate the soil, and once they die, their bodies serve as an important source of nitrogen for growing trees.

Why does Brood X only come out every 17 years?

As trees go through their seasonal cycles, shedding and growing leaves, the composition of their sap changes. And when cicada nymphs feed on that sap, they likely pick up clues about the passage of time. The 17th iteration of the trees' seasonal cycle gives the nymphs their final cue: it's time to emerge.