Annual or "dog-day" cicadas emerge throughout the summer every year and buzz all summer long. Chances are you have already started to hear them along with a sub-brood of periodical cicadas, which are part of the large Marlatt's XIII brood.
In northern Illinois, the Marlatt's XIII brood of periodical cicadas emerges every 17 years, all at once. Right now, these creatures are still under the ground and we won't see them emerge until May 2024. In the southern parts of the state, the periodical cicadas emerge every 13 years.
Dr. Ted Burgess is an undergraduate academic advisor for the Department of Biological Sciences at Northern Illinois University. He said all cicadas, and their exuviae -- the casings left behind on tree bark -- are a great way to introduce kids to the world of insects.
"I know when I was a kid, they were always really fascinating to me," Burgess said. "I would walk along our neighborhood and find all the trees that had the exuviae attached to them, and collect them, and see how carefully I could pick them off the tree so that their legs didn't fall off."
Most exuviae are found on trees, but the insect will sometimes attach to the outside of a garage or house.
Periodical cicadas have dark bodies, bright translucent wings, and red eyes. Annual or dog-day cicadas are mostly green, with red eyes.
Cicadas only live in North America. "They're not found in any other countries on any other continent," said Burgess. "They are a natural phenomenon that is unique to the upper Midwest."
They can be found in southern Wisconsin and "a little bit" in Iowa and Indiana, he said, but Illinois is home to the largest brood. The periodical cicada is the longest living insect known to mankind, with a lifespan of 17 years. "That's unheard of in the insect world," Burgess said.
Most of a cicada's life is spent underground "except for the few weeks they emerge as adults when they mate and lay eggs," Burgess explained. The eggs are the beginning of the life cycle.
"Once the adults mate, the female lays eggs," he said. "They make a little slit in a thin branch. They lay their eggs in that slit and the eggs hatch."
Burgess said when the nymphs hatch, they fall out of the slit and land on the soil beneath the tree.
"Then they start to burrow into the soil," he said. "They find a tree root and latch onto it and begin feeding."
This is one of five "instars" or "developmental stages" of this arthropod. Burgess said because they live underground, there are still a lot of unknowns about the mysterious insect.
"There's not a whole lot of research done on these periodical cicadas," he said, "so we're not 100% sure what the nymphs are doing -- intimately -- underneath the soil, attached to the tree roots." Burgess said he doesn't know how much they move or how much they eat but said after 17 years, "When the soil temperature becomes right, they crawl out of the soil, climb up a tree, do their last molt where they shed their exuviae, and then start the whole thing over again."
If cicadas eat tree roots, what eats cicadas? Burgess said, "Anything that feed advantageously on arthropods." This includes birds, fish, reptiles, arachnids, and opossums. But pets and humans are also known to indulge.
"They're thought to taste like almonds," said Burgess. "In fact, if you microwave them, they give off an almond smell." He said even though the insect is edible, is protein dense, and were once a part of an Indigenous diet in the United States, he does not advocate for people to collect and eat them.
Another cicada predator is the cicada killer wasp.
"They catch cicadas. They paralyze them," he said. "They bury them in a nest and they lay eggs in them. And then their young basically eat the cicada."
Burgess said cicada killer wasps are not aggressive toward humans. "They aren't going to murder humans or your pets or anything like that."
Insects play a role in the biological life cycle. Burgess said that cicadas are harmless to trees and to humans. Instead of spraying insecticide, he urges people to celebrate the unique insect.
"They are a treasure to the Midwest and people should feel a sense of pride that every year we get to hear this sound," he said. And, he added, "It is definitely a comfort. It lulls them [people] to sleep like a bullfrog out in the backyard or in the back pond."
Annual cicadas are part of the authentic Midwestern experience that we get to appreciate every year, but, Burgess said, "2024 is when the really big brood of periodicals is going to emerge. That's when we're going to have the 100-decibel anthem of mating calls in the air."