• Science
  • animals

Two Broods of More Than a Trillion Cicadas Will Emerge in the U.S. This Year

3 minute read

More than a trillion cicadas will be coming to the U.S. in an event that has not happened since Thomas Jefferson was U.S. president in 1803.

Two adjacent broods of the red-eyed flying cicadas will emerge from the ground in April, and residents in the Midwest and Southeast should brace themselves for a season of high-pitched buzzing. 

Cicada broods often emerge together, the University of Connecticut says, but 2024 will mark the first time in more than 200 years that Brood XIX, which arrives every 13 years, and Brood XIII, which arrives every 17 years, will emerge at the same time. 

The next co-emergence of these broods won’t happen for another 221 years. 

Here’s what to know.  

More From TIME

What are cicadas?

For more than a decade, cicadas, which are in the same family as stink bugs and bed bugs, live in underground burrows until they are mature enough to rise to the surface. Weeks before they are set to emerge, the insects create tunnels to the surface, but do not come out of their homes until soil temperatures at a depth of 7-8 inches are about 64 degrees Fahrenheit.

Cicadas are unique because of their lengthy lifespan. But they don’t live long once they emerge from the ground— they only have four to six more weeks to mate. 

Periodical cicadas are about 1-1.5 inches long, though their wingspan is about double that length. They can be distinguished by their orange-colored veins and large red eyes. There are seven different species of cicadas, three of which surface every 17 years, while the remaining broods emerge every 13 years. 

Most cicadas are timely, but some may emerge a year late, or they may “count the years” incorrectly. For instance, thousands of cicadas emerged in the year 2000, four years ahead of schedule. 

What to expect 

Cicadas will become a sight to see across several states, though as few as two—Illinois and Indiana—will be able to see both broods. Brood XIII will be seen in states like Iowa, Wisconsin and possibly even Michigan. Brood XIX will emerge in Alabama, Arkansas, Georgia, Kentucky, Louisiana, Missouri, Mississippi, North Carolina, Oklahoma, South Carolina, Tennessee and Virginia. 

While the mating call of these insects may be annoying, cicadas are harmless to humans. They don’t sting or bite, and are not poisonous. In fact, the Environmental Protection Agency (EPA) says they can be a great food source for birds and are nutritious for the soil once they decompose. They may be damaging to young trees if female cicadas decide to lay their eggs in one. To better protect a tree, the EPA suggests covering them in mesh or netting with ¼-inch holes or smaller.

Cicada Safari, a website created by Mount St. Joseph University, says people can wrap the branches with cheesecloth to keep cicadas away. But cicadas won’t be harmful to any flowers or fruit, because they only consume sap from trees and shrubs to stay alive. Pesticides do not work on cicadas.

The insects are generally beneficial to local ecology. “Their emergence tunnels in the ground acts as a natural aeration of the soil. The large number of adult cicadas provides a food bonanza to all sorts of predators, which can have a positive impact on their populations,” Cicada Safari says.

More Must-Reads from TIME

Contact us at letters@time.com