A symphony of cicadas with distinct red eyes and orange-veined wings will soon reverberate across Central Illinois, the likes of which hasn’t been heard here in 221 years.
For the first time since 1803, two broods of cicadas are emerging simultaneously near Illinois State University’s campus: the 13-year cycle Great Southern Brood and the 17-year cycle Northern Illinois Brood.
“We just happen to be in the right location in time and space where two broods are coming out, and we are on the border between the two broods,” said Dr. Scott Sakaluk, a Distinguished Professor emeritus in Illinois State’s School of Biological Sciences. “It’s a very unusual event.”
Periodic cicadas, such as those in the Great Southern and Northern Illinois broods, spend most of their lives underground in larval form. Billions of the bugs emerge as adults when the soil reaches 64 degrees, and they live for just a few weeks—long enough to mate and lay eggs.
“It’s really a marvel of engineering that something that small can produce a sound that loud.”
Dr. Scott Sakaluk
“The males come out, and they sing,” Sakaluk said. “They prefer to aggregate in assemblages with lots of other males in trees, which acts as a huge acoustic beacon and draws females from all over the place to mate.”
For small insects, cicadas create a lot of noise. The males have discs in their thorax called tymbals that pull in and pop out rapidly to produce sound. Their hollow abdomen acts as a resonance chamber to amplify their unmistakable songs.
“It’s really a marvel of engineering that something that small can produce a sound that loud,” Sakaluk said.
After mating, the females pierce branches or twigs to lay clusters of eggs—between 600 and 1,000. This process can occasionally damage young trees or bushes, which is why some orchards refrain from planting new trees during years when periodic cicadas emerge. Netting can also be used to create a barrier.
When the cicada eggs hatch, cicada larvae burrow into the ground where they’ll live for the next 13 or 17 years, depending on the species. Sakaluk said it’s widely believed by researchers that the periodic cicadas’ lengthy underground lifespan is an antipredator adaptation.
“They’re, in a temporal way, escaping their predators,” Sakaluk said. “Then, they emerge in these unbelievable numbers.”
At their peak of emergence, there can be between 300 to 600 adult cicadas per square meter, according to Sakaluk.
“That’s ridiculous!” Sakaluk said. “What they’re doing is vastly outstripping the ability of the local predator populations to make a dent in their population. The name of the game is to persist, and one way to do that is to over-satiate your potential predators. It’s incredible.”
Sakaluk expects a cicada symphony in Central Illinois from mid-to-late May through mid-June. During that time, he said they provide a “bonanza of protein” for birds, lizards, and mammals.
“They’re like little packets of protein,” Sakaluk said. “They’re non-toxic and they don’t bite, so they’re kind of defenseless and an opportunity for easy food.”
As a member of Illinois State’s house wren research group, Sakaluk is hopeful that racoons who often climb into nests to eat baby birds will instead gorge on the ample supply of cicadas.
“We get a lot of raccoon predation,” Sakaluk said. “I’m curious to see what happens.”
Once the billions of adult cicadas die out by the end of June, Sakaluk said their decomposing carcasses will add a welcomed boost of nitrogen to the soil.
And the tree canopies will become noticeably quieter.
Sakaluk said he is excited for the cicadas to emerge in a “wonder of the natural world” that won’t be seen, or heard, again until 2245.
“It’s such an unusual phenomenon,” he said.
Cicada concert on the Quad
Dr. Karen Power, a composer from Ireland who blends natural soundscapes with composed music, is traveling to Central Illinois to experience the sound from the dual cicada broods. She will visit Illinois State Tuesday, June 11, for a “listening session” on the Quad from 3-3:45 p.m. (meet in the Center for Performing Arts lobby at 3 p.m.), followed by a lecture and performance from 4-5 p.m. in Kemp Recital Hall, organized by Illinois State’s School of Music.
