How Cicada Fungus Makes the Bugs Try and Mate Like Crazy So It Can Spread On 5/24/21 at 12:53 PM EDT Periodical cicadas are seven species from the genus Magicicada that emerge from the ground every 13 or 17 years in North America. The cicadas that will burst from the ground in 2021 are referred to as "Brood X." These cicadas spend most of their lives underground as nymphs, but when the 13- or 17-year period is over—depending on the species—the insects crawl out of the soil and molt, transforming into their adult phase. During this phase of their life, the cicadas mate and lay eggs.