Cicadas spend the vast majority of their lifetime—more than 90%—underground. But this spring, two broods of more than a trillion cicadas will make their debut above the soil across the Midwest and Southeast in an event that has not happened in more than two centuries.
“When these emerge, it really is a unique, natural phenomenon,” says PJ Liesch, the director of the University of Wisconsin-Madison Insect Diagnostic Lab, who compares the insects’ emergence to that of Monday’s total solar eclipse. “If you think about your entire lifetime, you might only have a few opportunities ever to be able to see an eclipse. And for these periodical cicadas, it’s very similar.”
Cicadas have already begun to emerge in some Southern states including North Carolina and Georgia. The insects, which have been living underground for more than a decade, begin to dig upwards when the soil temperature reaches around 64 degrees Fahrenheit or more.
“Once that happens, you often have a decent rain shower , that can be a trigger to cause this emergence. So that’s what we’re starting to see in some parts of the U.S. For us in Northern Illinois and in southern Wisconsin it’s probably going to be another month, month and a half before we see the bulk of our activity at more northern parts of the cicada range.”
Here’s what to know about the cicadas.
What are the two broods of cicadas emerging?
There are two adjacent broods of cicadas that will be emerging at the same time. Brood XIX reside in Alabama, Arkansas, Georgia, Kentucky, Louisiana, Missouri, Mississippi, North Carolina, Oklahoma, South Carolina, Tennessee and Virginia. Brood XIII could be seen in Iowa, Wisconsin and possibly even Michigan.
What do cicadas do?
Cicadas have a lengthy lifespan of either 13 or 17 years, depending on the brood. There are three species of 17-year cicadas, and four species of 13-year cicadas. The insects live almost their entire lives at a soil depth of anywhere from eight inches or more, according to Liesch. During the time they are burrowed underground, they typically tunnel around and feast on the sap of tree roots as a source of food.
Once they emerge, male cicadas begin to buzz using tymbals that are attached to the sides of their abdomen. The noise functions as a way to attract a female partner and reproduce. Cicadas are some of the loudest insects in the world, according to the Center for Disease Control and Prevention. Besides the shrieking buzz, however, the insect is harmless to humans.
“After mating, the females have a structure called an ovipositor, and what it allows the female to do is go to twigs or branches and cut a small slit where she is going to insert a batch of eggs. That might be 10 or 20 or so eggs, and she’s going to repeat this process,” says Liesch. “It’s somewhat analogous to if you took a pocket knife and started cutting little slits in twigs.” Liesch adds that the damage to the trees is minimal, and does not really impact the health of the tree in the long run.
How do cicadas impact the environment?
Experts say cicadas are beneficial to the ecosystem.
“When they emerge from the ground, they are tunneling up and if you’re in a cicada hotspot, there’s going to be dozens, if not hundreds of holes in the ground in a relatively small area,” says Liesch. “That is very similar to if you get your lawn aerated by a lawn care company and that can allow oxygen to permeate into the soil better. It can perhaps alleviate soil compaction to a certain extent and allow water to flow into the ground better.”
Cicadas are also a great meal for other wild animals in the area. Turtles, fish, birds, skunks, and raccoons enjoy feasting on the insect. Dogs can also eat cicadas, though most veterinarians suggest they only ingest a few. Humans can also eat them.
“Also once all these millions of cicadas die, they are going to fall to the ground in those areas they’re going to break down and decompose and the nutrients will be returned to the ecosystem,” Liesch adds. “So it’s essentially free fertilizer to the lawn in those areas when you think about it.”
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