Cicadas in St. Louis: What you need to know

Spring and summer may look and sound a little different in the St. Louis area this year thanks to a massive incoming brood of periodical cicadas.

With around 60 billion cicadas expected in St. Louis City alone, the bug experts at the Sophia M. Sachs Butterfly House are sharing their expertise to help you prepare for the summer of cicadas.

In this blog:

What is different about these cicadas?

Short answer: Periodical cicadas emerge every 13–17 years instead of every year, are shorter than annual cicadas, and are red/orange in color instead of the black/green we seen in annual cicadas.

Long answer: Periodical cicadas are different first in that they have a long stretch of being underground, sometimes 13 years or 17 years. During this time, they are feeding on tree sap, sucking the plant juices through their roots.

“All cicadas have a similar life cycle, with most staying underground 2-5 years, but periodical cicadas have evolved to really take their time,” said Tad Yankoski, Senior Entomologist at the Sophia M. Sachs Butterfly House. “It is believed that because plant sap is a relatively poor source of nutrition, this slowed cicada’s developmental time considerably compared to most other insects.”

*A periodical cicada during the 2011 emergence, photographer in Chapel Hill, North Carolina. Photo by Philip N. Cohen/ Wikipedia Creative Commons.*

Annual cicadas on the other hand come out each summer, usually at dusk or at night. They are called annual cicadas because you see them every year, but they live underground for 2-5 years before coming out. Their generations overlap so they come out consistently each year.

Periodical cicadas and annual cicadas also look different. Most annual cicadas are black and green and 2-3 inch length. Periodical cicadas are the red/orange and are 1–2 inches in length.

This spring and summer, St. Louis will see both the annual cicadas that are with us each summer, as well as the 13-year periodical cicadas.

Will St. Louis experience two broods of cicadas?

*This is a USDA Forest Service map shows county-by-county, where periodical cicada broods of the United States are located, and when they have emerged or are expected to emerge.*

Short answer: No. St. Louis will only experience Brood XIX.

Long answer: Two independent populations of periodical cicadas, referred to as “broods”, are expected to emerge simultaneously this spring, something that has not happened since 1803— but only one will emerge in St. Louis.

“Brood XIX are 13-year cicadas that will be emerging in the St. Louis area this year,” says Tad Yankoski, senior entomologist at the Sophia M. Sachs Butterfly House. “Brood XIII consists of a population of 17-year cicadas that are emerging from Eastern Iowa through North-central Illinois and into North-Western Kentucky. While it is unlikely that the St Louis area will be effected by both broods at once, there are some areas in Illinois, Kentucky and Iowa were the two broods may slightly overlap and get even more cicadas emerging than normal.”

Brood XIX was last seen in 2011 in and will not be seen again until 2037.

How many cicadas will St. Louis see?

Short answer: As many as 1.5 million per acre

Long answer: In a city of about 40,000 acres, with each acre holding 1.5 million cicadas, there could be as many as 60 billion cicadas coming out of the ground in just St. Louis City.

“Imagine as many insects as you possibly can coming out of the ground in a very short window of time. Now add some more—a lot more,” Yankoski said. “They’ll be everywhere, they’ll be loud, and you won’t be able to avoid them.”

To help visualize, Yankoski said imagine a football field. About 2 million cicadas will emerge from an area that size, collectively weighing over 8,000 pounds— or more than a hippopotamus!

When should we expect cicadas to emerge

St. Louisans gather at the Whitaker Festival at the Missouri Botanical Garden. The musicians at this spring/summer music festival will likely be accompanied by the sounds of cicadas. Photo by Sundos J. Schneider/Missouri Botanical Garden.

Short answer: May–June

Long answer: Periodical cicadas emerge when the ground reaches approximately 64 degrees Fahrenheit.

But, we know Missouri weather can be unpredictable, with temperature changes. An unseasonably warm or cool spring could speed up or slow down their peak by a few weeks in either direction.

“You can expect to see the adult cicadas out for about 6-8 weeks, with the middle half of that time being filled with the loudest of their singing,” Yankoski said.

Are these cicadas dangerous?

Short answer: No. But their presence can feel overwhelming for some.

Long answer: Periodical cicadas don’t bite or sting, and they lack venom and aren’t poisonous.

The biggest nuisance factor will just be how many of them there are and how loud they will be. The noise made by the mating cicadas can reach 100 decicbels, or as loud as a lawnmower.

The cicadas may also fly right into you, but mean you know harm.

“Expect anything happening outside, from picnics to driving, to be impacted by millions of these amazing insects,” Yankoski said. “Though each year there will be stories about accidents caused by cicadas flying through car windows or even accumulating in such numbers on roadways that they become unsafe, overall their direct impact on humans is low. “

Jessika Eidson | Public Information Officer

Thanks to Tad Yankoski, Senior Entomologist for the Sophia M. Sachs Butterfly House for lending his expertise for this blog.

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