Cicadas may emerge earlier in Illinois as climate changes, experts say

As Illinois awaits a massive, rare double-brood emergence of cicadas, entomological research shows that the insects may come earlier.

This year, two 'periodical' cicada species—Brood XIII and Brood XIX— will emerge simultaneously. Maps of Illinois show where each brood is expected to flourish. 

According to Jennifer Rydzewski of the Forest Preserve District of DuPage County, brood XIII occurs in the Chicago area only every 17 years, while Brood XIX occurs every 13 years.

"So the 13-year and 17-year life cycles only align every 221 years," Rydzewski told CBS Chicago in an e-mail.

"Periodical cicadas have typically emerged in late May or early June in northern Illinois," said Dr. Ken Johnson of the University of Illinois. However, because of the urban heat island, that might happen earlier in Chicago. 

How will cicada behavior change? 

But as Chicago bakes in its third-warmest year on record, is a species directly cued by soil temperatures warming to 64 degrees being affected by the warming climate? Some cicadas were reported last week in the northwest suburbs. 

According to the University of Connecticut's Climate Change and Periodical Cicadas, "All available evidence indicates that the climate is warming and precipitation patterns are changing, and because some parts of the periodical cicada life cycle seem sensitive to these factors, it follows that these insects will be affected by climate change."

That study predicts that warming climates will cause periodical cicada emergences to start earlier in the year since spring will arrive earlier as the climate warms. Climate-related disruption of the cues periodical cicadas use to pick their year of emergence will lead to an increase in unexpected, oddly-timed emergences or even the breakdown of these insects' periodicity. 

The study mentions notable off-cycle emergences have already occurred, such as the unexpected emergence of Brood X cicadas in 2017.

"It's possible we are a few days ahead of schedule this year due to the warming climate, but we definitely need more data and analysis," Dr. Catherine Dana of the Illinois Natural History Survey said.

Periodical cicadas' long life cycles and rare emergences make gathering that data a lengthy process – but the periodical cicada mapping project is trying to accomplish that goal.

However, as the Connecticut study states, "It will take a while to collect the data, and the project involves multiple generations… of cicadas and researchers alike."

How long will cicadas be around in Illinois?

Periodical cicadas spend most of their time living underground, feeding on tree roots. Once the soil warms enough, they begin to emerge above ground.

According to the University of Illinois, adult cicadas spend most of their time above ground reproducing. Male cicadas start singing four or five days after they emerge.

After mating, the female cicadas will lay their eggs, about 500 to 600 each.

The adult cicadas will begin to die after about a month. That should happen before outdoor Ravinia Festival concerts kick into high gear. 

When will periodical cicadas emerge again in Illinois after 2024?

About six to ten weeks after they are laid, the eggs begin to hatch. The tiny cicada nymphs drop to the ground and begin feeding, often on grass roots.

Eventually, they dig into the soil about 8 to 12 inches deep and feed on tree roots for 13 to 17 years.