Everything you need to know about Wisconsin’s summer cicada emergence

Seventeen years ago, parts of Wisconsin were suddenly swarming with cicadas and their loud humming song for a few brief weeks. Those cicadas participated in a mysterious courtship ritual, singing loudly, mating, and then almost immediately dropping dead.

Soon, millions of those cicadas’ descendents will begin emerging above ground, the next round of a 17-year pattern for this group of periodical cicadas, called Brood XIII or the Northern Illinois Brood.

While so-called dog day cicadas emerge in Wisconsin every year later in the summer, Brood XIII will add the songs of hundreds of thousands to the noise starting in late May or early June. The event will be loud, short-lived and a natural marvel, said University of Wisconsin–Madison Extension entomologist PJ Liesch.

“It’s this amazing natural phenomenon that for someone living in Wisconsin, you only have maybe a handful of opportunities in your entire life to witness this here in the Badger State. So it’s really a unique, cool experience to see,” he said.

These insects are typically between 1-1.5 inches in size, or roughly the size of a shrimp, with transparent wings and bulging red eyes. And they’re loud: A group of cicadas can create a chorus of noise that can reach upward of 80 to 100 decibels, similar to an alarm clock or a blender.

Wisconsin is on the edge of a larger, more rare convergence of two broods that haven’t appeared at the same time in 221 years, when Thomas Jefferson was president and the Louisiana Purchase was made. Wisconsinites won’t see any cicadas from the other group, Brood XIX or the Great Southern Brood, which emerge every 13 years, unless they travel south to Illinois.

Where can you see Brood XIII in Wisconsin?

These 17-year cicadas won’t be as widespread as you might think, Liesch said. Instead, they’ll stick to hot spots throughout the state’s southern counties.

“Think of it more as individual pins on a map. It turns out that these insects have a very isolated distribution, so you can have them in one spot, and you drive 20, 30 minutes down the road and you may not have any at all,” he said.

Lake Geneva has historically been a hot spot for seeing and hearing these insects, Liesch said. In a July 6, 2007, story, the Kenosha News reported that Big Foot Beach State Park on the shores of Geneva Lake was one of the best locations to spot the cicadas.

Other notable epicenters are the Janesville, Beloit, Prairie du Chien and Spring Green areas. For more details on good viewing locations in specific counties, visit cicadas.wisc.edu.

Some of the first signs of the cicadas’ arrival will be emergence holes in the ground. In some hot spots you could have anywhere from dozens to hundreds of thousands of these burrows per acre, Liesch said.

The insects tend to emerge in the evening or after dark. With a flashlight you may spot nymphs crawling across the ground at night looking for something to latch on to.

What will the cicadas do above ground?

The insects have a pretty strict agenda once they emerge from their underground homes: molt, sing, mate, then die.

They’ll still be adolescents, or nymphs, when they first come out. For the first few days they’ll cling to vertical surfaces, such as tree trunks or fence posts, and eventually they’ll molt their exoskeleton and mature into adults.

They won’t waste much time after that finding a mate. In a matter of days they will start to call out to potential partners, a humming, sci-fi-like chorus of cicadas searching for love. Liesch said that the males are the ones who will be making most of the noise, but the females will also be heard flicking their wings.

After the cicadas mate, the females lay their eggs by cutting slits into twigs and branches on trees. One female cicada can lay hundreds of eggs. Then the adults die, living only about a month above ground.

The new generation of cicadas will hatch and burrow underground to live for another 17 years. We won’t see them again in Wisconsin until 2041.

Are cicadas harmful?

Generally, cicadas do more good than harm, Liesch said. One of the main positives of their arrival is that other animals will get to feast on them.

“All sorts of wildlife will gorge themselves on these insects. It is going to be a free smorgasbord for wildlife — fish, turtles, various birds, mammals will gorge themselves on these,” he said.

Since they emerge in droves of hundreds of thousands or even millions, predators will eventually eat their fill, leaving behind plenty to reproduce. It’s one of scientists’ theories on why periodical cicadas emerge so infrequently and abundantly, Liesch said.

The holes the insects dig in the ground can also be a natural aeration process for lawns, and when the bug dies, its corpse provides nutrients to the soil.

There’s the chance that the bugs could damage some young trees when laying their eggs. Liesch said you can place a mesh netting over any newly planted trees to protect them while the cicadas are here, but that mature trees shouldn’t be affected.

Cicadas may briefly mistake a human for a tree, but they don’t bite or sting. Instead, the noise from the bug’s synchronous mating song will impact humans most. This could interfere with outdoor events if you’re in a hot spot, and Liesch said residents may want to think about postponing or relocating events.

“The cicadas themselves are really pretty harmless. They might be a little bit of a nuisance because they will of course be loud in cicada hot spots,” he said. “But it’s just this really surreal natural phenomenon to see.”