“Then there’s big piles of dead, stinky cicadas on the ground for a long time. And then everybody forgets about it,” Weiss said.

Six weeks later, the eggs will hatch. Tiny nymphs, or young cicadas, will float down like snowflakes and burrow underground, where they will stay for the next 13 or 17 years depending on the cycle of their brood.

“How do they tell time? These little tiny things go into the ground, and how do they know without their watches, without their iPhones, without their calendars?” Weiss observed. “Everybody is by themselves, it’s not like they’re going to meet at the coffee machine or the water cooler to chat about how your summer vacation was up there.”

Biologists believe cicadas keep track of the years as they feed from a tree’s sap, sensing patterns from the seasonal flow of water through the tree, Weiss said; the insects probably have a molecular mechanism that allows them to follow this passage of time.

Effects of climate change

Periodical cicadas will stay underground until the soil 8 inches deep reaches a temperature of 64 degrees. In Illinois, that typically occurs around the last week of May or the first week of June.

But climate change may throw a wrench in the plans of scientists and enthusiasts hoping to visit Illinois to study and view two cicada broods at the same time. After a warm winter, the soil might reach the necessary temperature earlier.

“We’re kind of anxious because we’re planning our trip to Chicago based on our best guess on when the cicadas are going to be emerging,” Lill said. “And the kind of winter and spring that you guys are having there is making us … nervous because we kind of thought we’d know when to come, but now we’re not really sure.”

Extremely cold winter and spring seasons in the past have pushed some cicada emergences to happen a few weeks later, Lill said. But it has rarely happened significantly earlier in a given year.

“That’s one of the predictions of climate change,” he said. “If (emergence) really is guided totally by soil temperature, and it’s been a crazy warm spring, we’ll see what’s going to happen.”

Some periodical cicadas, however, have emerged four years before or after their brood was supposed to, according to Chris Simon, professor of ecology and evolutionary biology at the University of Connecticut, who alongside a colleague maintains cicadas.uconn.edu, a website with data on periodical cicadas.

“With climate change, we’re seeing more and more of them come out four years early,” she said. “That happened in the Chicago area four years ago.”

Because periodical cicada species have existed for millions of years, they have undergone and survived substantial periods of climate change in glacial cycles. But they have still been affected by past changes in climate patterns and will likely be affected by current and future climate change events.

If cues like soil temperature are disrupted by changes in climate, it might lead to more unexpected cicada emergences. Periodical cicadas might also experience permanent life cycle switches: For example, 13-year broods might come out four years earlier and become nine-year broods, or 17-year broods might come out four years later and become 21-year broods.

Permanent changes in life cycles can make these insects more vulnerable to predators.

Because of their vulnerability to climate, periodical cicadas can be considered an indicator species, Simon said. This means that, like a canary in a coal mine, they can signal environmental dangers.

Erasing misconceptions

Many experts are enthralled by cicadas and eager to erase popular misconceptions about the insects.

“There’s often a lot of language that makes people scared of them or view them as some alien invader, enemy kind of thing,” Weiss said. “First of all, they’re totally harmless. They couldn’t bite you if they wanted to. They can’t sting. They’re not spiny, they’re not poisonous.”

Hundreds of years ago, when early colonists in the United States encountered cicadas they confused them with locusts — grasshoppers that migrate in swarms and can be devastating to crops. The Bible and Quran mention ancient locust plagues that caused famine and human displacement across the Mediterranean and North Africa.

“There was a misconception that the cicadas were actually eating agricultural crops and commodities, and that couldn’t be further from the truth,” Lill said. “(There’s) no danger to Illinois soybean fields and no danger to your pansies and your marigolds and whatever you’re planting in your garden.”

He said small saplings might be somewhat vulnerable to cicadas laying eggs in their branches, but that can be avoided by covering the plant with netting for a couple of weeks.

“You probably could wrap trees effectively,” Weiss said. “I think that it’s not necessarily time or money well spent. (Cicadas) have been around for millions of years and we still have trees.”

“There’s a lot of people that want to make money off of fear,” Lill said. “They’re trying to sell pesticides, and the worst thing you could do is spray a bunch of chemicals on your yard because you’re scared of cicadas. You’re doing way more harm than good, and you’re not going to really affect the cicadas, to be totally honest.”

“Instead, we just encourage you to embrace (them), bring your kids out at night and watch this amazing phenomenon and get them excited,” Lill continued. “And they will remember it for the rest of their lives.”

Weiss said her daughter and her friends, who were 7 years old during the 2004 cicada emergence in D.C., still remember staying up until late at night to watch cicadas crawl up trees.

“When they see me, they say ‘You made me eat chocolate-covered cicadas!'” she said. “They’re 26 now. … They say, ‘Remember when the cicadas came out and we got to go watch them crawl up?'”

Now that their children are grown up, Lill and Weiss are hoping to keep working with educators and younger generations to show how these insects are cool and exciting rather than scary.

“We felt like it was almost entomological malpractice not to put together an education campaign,” Weiss said.

The researchers have worked alongside Lill’s wife to create a set of digital learning materials, available on their website at friendtocicadas.org, which includes lectures and workbooks about cicadas through the lenses of biology, history, music and art. It will soon be updated with information on Brood XIII and Brood XIX.

“The other thing that is important to recognize is that they are always here,” Weiss said. “We’ve come in and ended up in their habitat … They’ve been here the whole time, they’re underground, they come up and say hello for a few weeks every 17 years, then they go back.”

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