A rare double-emergence of periodical cicadas is getting underway in the eastern United States, and Illinois is right at the confluence of an event that hasn’t occurred in 200 years.
Periodical cicadas, which only exist in the eastern United States, emerge on 13 or 17-year life cycles, and two broods that are both present in Illinois will actually emerge at the same time, according to experts.
Just how rare is this double emergence? What threats do these periodical cicadas pose? And how can you cope with their emergence?
Here’s a look at what you should know about the rare and historic moment:
Just how rare is this dual emergence?
According to the University of Illinois, Broods XIII and XIX are both emerging this year in different parts of the state, though there will be overlap in some central portions of Illinois.
While the broods do emerge periodically, as their names imply, they very rarely do so at the same time. According to the university, this marks the first dual-emergence of Broods XIII and XIX in 221 years, with the last occurring during the administration of President Thomas Jefferson.
In fact, it will be another 221 years before such a dual emergence occurs again, with the next one set for 2245, according to experts.
Where will the emergences occur?
For the Chicago area, Brood XIII will be most seen in parts of northern Illinois and Indiana, and possibly even in Wisconsin and Ohio, Dr. Gene Kritsky, dean of Behavioral and Natural Sciences at Mount St. Joseph University in Cincinnati, said.
The Northern Illinois Brood itself is huge, with a reputation for the “largest emergence of cicadas anywhere,” according to the University of Illinois.
In 1956, entomologists reported as many as 311 “emergence holes” per square yard in a forested floodplain near Chicago, which experts say translated to 1.5 million cicadas per acre, according to the University of Illinois.
“When the cicadas start dying and dropping from the trees later in the spring, there are large numbers on the ground, and the odor from their rotting bodies is noticeable,” U of I reports. “In 1990, there were reports from people in Chicago having to use snow shovels to clear their sidewalks of the dead cicadas.”
Meanwhile, Brood XIX, or the Great Southern Brood cicadas, have a more widespread population, covering parts of Missouri, Illinois, Louisiana, North Carolina, Virginia and Maryland.
“Brood XIX is arguably the largest (by geographic extent) of all periodical cicada broods, with records along the east coast from Maryland to Georgia and in the Midwest from Iowa to Oklahoma,” the University of Connecticut reports. “Although 13- year cicadas are generally considered to have a southern distribution, the northernmost known record of this brood is in Chebanse, IL, roughly 75 miles from Chicago’s Loop.”
Where in Illinois are the cicadas expected?
Across most of Illinois and the Chicago area at least one of the two broods is likely to emerge, but in a narrow part of the state, both could emerge at the same time, in the same place.
“This is like the year for Illinois,” cicada expert Catherine Dana, an affiliate with the Illinois Natural History Survey, told NBC Chicago. “We are going to have cicadas emerging all over the state.”
Here’s a map of what to expect in Illinois, according to data from the USDA Forest Service.
“Somewhere around Central Illinois, probably like around Springfield, is what some researchers are predicting we may see some overlap of these two … different broods,” Dana said. “It’s not going to be a large area. But there will likely actually be some mating happening between these two broods, which is going to be really exciting.”
When are cicadas set to emerge in Chicago and Illinois?
The emergence has started earlier than average in Illinois.
“The periodical cicadas have been emerging for the last week and a half,” Stephanie Adams, plant pathologist at Morton…
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