Trillions of cicadas set to emerge in U.S. When do the cicadas come out in Illinois?

Over a trillion periodical cicadas will emerge this spring across much of the United States after over a decade spent underground. Millions of the loud, large insects will appear in Illinois. Nonetheless, it will be a rare event.

While annual cicadas emerge every midsummer in Illinois, 2024 will feature an earlier, once-in-several-lifetimes event when two specific groups of periodical cicadas both appear as early as May. Brood XIII and Brood XIX emerge at intervals that only coincide once every 221 years. And they only occur adjacently in one area: a handful of counties in Illinois.

Here's more to know ahead of the massive emergence of the big, buzzing, red-eyed insects.

Cicadas 2024: Why Illinois will be a unique place for cicadas

Where are cicadas found in the U.S.?

Periodical cicadas are found in the eastern and Midwestern United States. Each of the many broods has a particular range. Brood XIII, also called the Northern Illinois Brood, only appears every 17 years. It also occurs in Iowa, Wisconsin, Indiana and possibly Michigan, says the University of Illinois Extension. Brood XIX, or the Great Southern Brood, will emerge in southern Illinois as well as Alabama, Arkansas, Georgia, Indiana, Kentucky, Louisiana, Mississippi, Missouri, North Carolina, Oklahoma, South Carolina, Tennessee and Virginia. It is on a 13-year cycle. Those two emergences rarely line up.

How deep do cicadas bury themselves underground?

After adult periodical cicadas emerge and their eggs hatch, the nymphs drop to the ground and dig about a foot into the soil, the University of Illinois Extension says. There, they feed on sap from tree roots for the next 13 or 17 years.

Cicadas map 2024: 'Trillions' of cicadas? See how and where dual cicada broods will emerge

How long do cicadas live above ground?

Periodical cicadas are among the longest-lived insects on the planet, but most of their 13- or 17-year lifespan is spent underground. After emerging, singing and reproducing, the adults don't live long. After about a month, they cicadas begin to die.

That can result in an odor and "paste" of dead and crushed cicadas. But cicadas are mostly beneficial.

What do cicadas eat?: Should Illinois be worried about the looming cicada emergence?

What are cicadas good for?

Cicada nymphs aerate the soil. Emergent adults prune mature trees and provide an abundant source of food for wildlife. They’re consumed by just about any creature that eats insects, says the National Wildlife Federation, which adds that humans who have sampled cicadas often say they taste like canned asparagus. Other reports say they taste like almonds or seafood. Many cicada recipes can be found online. After they die, cicadas' bodies provide a source of nitrogen for growing trees.

Ciadas 2024: Should homeowners and gardeners be worried about the cicadas?

This article originally appeared on Journal Star: When are cicadas coming back to Illinois?