Where are the Trillions of Cicadas Swarming the US Coming From?

Cicadas are insects that live underground and feed on roots for 13 to 17 years, depending on the species. As Raymond Goldstein, a physicist at the University of Cambridge, summed up, there is very little we know about cicadas. The United States has over a dozen cicada broods. This year, the Great Southern Brood and Northern Illinois Brood have emerged. The Great Southern Brood has emerged after 13 years across North Carolina and Georgia. The Northern Illinois brood is expected to come out of the ground next month after a 17-year cycle of living underground.

Cicadas come out only to mate, and the females lay eggs on tree branches. Young cicadas drop to the ground once they hatch and burrow into the soil. Since cicadas spend so little time above ground, there is  not enough information about them. However, Dr. Chris Simons from the University of Connecticut might have some new information for us. His team sequenced the genome of cicadas and believed that the emergence of so many cicadas all at once might be a behavior lodged in how their genes work.

The grand emergence of so many cicadas at once might be an evolutionary method to increase the odds of surviving. While many cicadas may get preyed upon, the rest can mate and produce many young cicadas.

One clue about the emergence of cicadas from the ground below lies in the soil temperature, which needs to cross a threshold of 64 degrees for an emergence to take place. However, this theory is somewhat faulty in the sense that the soil might not be equally warm, and cicadas can crop up in small groups depending on how the warmth of the soil changes.

However, a different hypothesis comes from a math model speculating that cicadas “eavesdrop” on the actions of neighboring cicadas. Cicadas are more likely to emerge when a neighboring cicada prepares to come out. Although the hypothesis is in its infancy, and there is no proven sign that cicadas can communicate, it indeed is a nice unification of biology and math models.

Copyright @smorescience. All rights reserved. Do not copy, cite, publish, or distribute this content without permission.

Join 20,000+ parents and educators
To get the FREE science newsletter in your inbox!