Usually around summer or spring, depending on the region, you'll hear a chorus that sounds like a very loud buzzing or whirring noise, shaking of maracas, or two percussion instruments being rubbed against each other. Cicadas make this familiar song to attract each other during mating season, and after two to six weeks, they die.
Many species of cicada generally have a life cycle between two to five years, but the eastern North American species of the genus Magicicada, have either a 13-year or 17-year cycle which means these cicadas spend 13 and 17 years of their lives respectively before coming up out of the ground for their once-in-a-lifetime venture into the outside world to mate and die.
This year marks the first time in more than 200 years when two different broods of cicadas will be emerging simultaneously. Brood XIII from the 17-year group and Brood XIX from the 13-year group will be emerging from Illinois and several other states which hasn't happened since 1803.
Why the Magicacada live for so long underground and go out in large batches, one can only speculate to be a strategy against predators. Being able to come up altogether in such a huge throng makes it impossible for birds or other predators to thin out the number making it easier for the cicadas to mate and secure their posterity.
The map above shows the different cycles and times for when each brood will be coming up and where. From this year until 2038 except 2026, there will be broods emerging on the eastern part of the US.
(Image credit: Andrew M. Liebhold, Michael J. Bohne, and Rebecca L. Lilja, USDA Forest Service/Wikimedia Commons)