Rare co-emergence of periodical cicada broods set to fill Midwest with song

A rare co-emergence of adjacent periodical cicada broods will occur across the entire state of Illinois and in parts of Missouri and other surrounding states, filling the air with the sounds of their noisy mating call.

After hatching, periodical cicadas spend 13 or 17 years — depending on the species — underground feeding on xylem sap from tree roots. Once the cicadas have reached adulthood, they emerge from the ground for a four- to six-week period where they will mate and reproduce.

This year, Brood XIII, also known as the Northern Illinois Brood, is a 17-year brood that will emerge at the same time as the 13-year Brood XIX, also known as the Great Southern Brood.

"If you get online, you can look up periodical cicada brood maps. ... They list each brood based on when they emerge, what year, so not everybody comes out at the same time," said Timothy Judd, chairman of Southeast Missouri State University’s Department of Biology. "One brood might come out one year and another brood will come out another year, but it will be every 13 or every 17 years depending on which brood you’re talking about."

According to research from the University of Connecticut, this is the first time since 1803 that these two specific broods will emerge, and it will be another 221 years until they emerge simultaneously again.

Even though the two broods are very close in proximity, they don’t overlap, although some cicadas from each brood may coexist in small patches of woods. According to Judd, Southeast Missouri will likely see cicadas from Brood XIX.

"I think we’re going to get some of the periodical cicadas," Judd said. "Looking at the map, I’ve looked at the Cape Girardeau areas within the boundaries, and it’s very possible that we will see them. They can be a little more spotty in areas than others, but the ones I’ve been looking at look like we might get hit."

Periodical cicadas are different from the annual cicadas we see each year. Aside from its life cycle, periodical cicadas are approximately 75% smaller than annual cicadas and are black instead of green. Periodical cicadas are known for their red eyes, although they can also naturally appear blue or white in presumed instances of mutations or rare alleles.

After emerging, the male cicadas will use their call to attract females to mate. The females will then lay their eggs inside the stems of woody plants.

Within two months of their emergence, the adult cicadas all die off. Cicadas act as prey to animals such as birds, reptiles, squirrels, cats, dogs and other mammals, and are sometimes even eaten by humans and other insects such as spiders, wasps and mantises. In addition, male cicadas often die from exhaustion because of their near-constant calling for mates.

"Males are going to be using up a lot of their energy calling," Judd said. "Basically, what happens is they have this structure in their body that kind of scrapes cuticles together, and that’s what makes the sound. It takes energy to do that if you want a loud noise. Imagine clapping for hours, it’s going to tire you out. Now you’re a little insect, and they always are going to be calling, calling, calling, calling, and then they’re going to run out of energy. They die from just exhaustion, essentially. The females will do their thing and then they just kind of die, too. Basically, all their energy is devoted to reproduction once they’re up and out of the ground."

While many people are afraid of cicadas because of their size and ability to fly, Judd explained that they do virtually no damage to people and the environment.

"They’re harmless," Judd said. Adults are out just to reproduce and that’s all they’re trying to do. ... They’re not going to do any harm. Some people think they damage trees, but they really don’t."