A rare double emergence of periodical cicadas is underway in the eastern United States, and Illinois sits 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 in 13- or 17-year life cycles, and two broods both found in Illinois will emerge at the same time, experts say.
How rare is this double emergence? What threats do these periodical cicadas represent? And how to deal with their emergence?
Here’s a look at what you need to know about this rare and historic moment:
How rare is this double emergence?
According to the University of Illinois, broods XIII and XIX are both emerging this year in different parts of the state, although there is overlap in some central parts of Illinois.
Although broods emerge periodically, as their name suggests, they very rarely do so at the same time. According to the university, this is the first dual emergence of Broods XIII and XIX in 221 years, the latter occurring during the administration of President Thomas Jefferson.
In fact, it will be another 221 years before such a double emergence occurs again, with the next one predicted for 2245, according to experts.
Where will the emergences take place?
For the Chicago area, Brood XIII will be most visible in parts of northern Illinois and Indiana, and perhaps even Wisconsin and Ohio, said Dr. Gene Kritsky, dean of behavioral sciences and natural studies at Mount St. Joseph University in Cincinnati.
The northern Illinois brood itself is enormous, with a reputation for “the largest cicada emergence in the world,” according to the University of Illinois.
In 1956, entomologists reported as many as 311 “emergence holes” per square meter in a forested floodplain near Chicago, which experts said translates to 1.5 million cicadas per acre, according to the University of Illinois.
“When cicadas begin to die and fall from trees later in the spring, they are in large numbers on the ground and the smell of their decaying bodies is noticeable,” reports the U. “In 1990, Chicagoans had to use snow shovels to clear their sidewalks of dead cicadas.”
Meanwhile, Brood XIX, or Great Southern Brood cicadas, have a more widespread population, covering parts of Missouri, Illinois, Louisiana, North Carolina, Virginia, and Maryland.
“Brood in Oklahoma,” reports the University of Connecticut. “Although 13-year-old cicadas are generally considered to have a southern distribution, the northernmost known record of this brood is in Chebanse, Illinois, approximately 75 miles from Chicago’s Loop.”
Where in Illinois are cicadas expected?
In most of Illinois and the Chicago area, at least one of two broods is likely to emerge, but in a narrow part of the state, both could emerge at the same time, in the same location.
“It’s like the year of Illinois,” cicada expert Catherine Dana, affiliated with the Illinois Natural History Survey, told NBC Chicago. “We’re going to see cicadas emerge across the state.”
Here’s a map of what to expect in Illinois, according to data from the USDA Forest Service.
“Somewhere in central Illinois, probably like around Springfield, some researchers are predicting that we might see some overlap of these two different broods,” Dana said. “It won’t be a big area. But there will probably be some mating between these two broods, which will be really exciting.”
When are cicadas expected to emerge in Chicago and Illinois?
Emergence began earlier than average in Illinois.
“The periodical cicadas have been emerging for the last week and a half,” Stephanie Adams, a plant pathologist at the Morton Arboretum in Lisle, said Tuesday of Brood XIII, which will soon spread throughout the Chicago area. “We found them both here in our landscape and also in our eastern woods.”
According to Adams, the emergence of the first cicadas occurs about two weeks earlier than the historical average. This will continue to be sporadic, as soil temperature, mulch, and turf all impact cicadas differently. For example, the ground is warmer near sidewalks, so cicadas in those locations should emerge more quickly.
Sightings of cicadas, many of which are still in the ground, have already been reported in many parts of the city and suburbs.
Cicadas typically emerge when the ground begins to warm in spring and early summer.
Cicadas have a lifespan of about four weeks and typically emerge in mid-to-late May and into June, when soil temperatures warm in spring and early summer.
“Research shows that the night at which periodical cicadas emerge depends on soil temperature,” the post reads. “Juvenile cicadas, or nymphs, emerge after a rainstorm when soil temperatures 8 inches deep exceed about 64°F.”
How long will the emergence of cicadas last?
Emergence is expected to last until mid-June.
Do cicadas sting?
Generally, cicadas are harmless, Adams said. They do not bite, do not have stings and are beneficial to the environment.
What do cicadas eat?
According to Orkin, cicadas have “piercing/sucking mouthparts (mosquito-like) that they use to feed on underground roots and young twigs.” But what they eat depends on their age.
Adult cicadas “feed on plant fluids from the young twigs of trees and woody shrubs,” Orkin reported.
Which trees will attract the most cicadas to your garden?
Cicadas can cause damage to small, vulnerable trees and shrubs, Adams said.
According to Adams, young plants, two to three years old, are most vulnerable, as are smaller plants, with branches less than two inches in diameter, which are at risk. They may not be able to recover from the damage caused by female cicadas laying eggs, Adams said.
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“This damage is caused when the female begins to lay her eggs,” Adams explained. “It has a specialized organ that cuts plants, trees and shrubs and lays its eggs inside the thin bark.”
According to the Arboretum, cicadas are “not peculiar,” meaning they use a variety of trees and shrubs as hosts.
“However, only very young trees or older trees in poor health or stress are at risk,” the Arboretum said.
The insects are known to lay eggs in oaks, maples, hickory, apple, birch, dogwood, basswood, willow, elm, ginkgo and pear trees, according to the Arboretum.
“Cicadas can also lay eggs in certain shrubs, such as rose bushes, lilacs and forsythia,” the Arboretum said. “They tend to avoid conifers like pine, spruce and fir.”
Arboretum records show that during the emergence 17 years ago, some of the plants most affected by the emergence were maples, cherries, ashes, hawthorns, willows, mountain ash, oaks , pear trees, rose bushes, privet, poplars, saskatoon berries and beeches.
According to the Arboretum, one way to protect your trees and shrubs would be to use tulle as a protective wrap and barrier. The tulle material is particularly recommended because it is breathable and allows sunlight to penetrate the plant.
“You’re looking for netting that’s no more than a quarter of an inch in diameter, the more the cicadas can climb and defeats the purpose of protecting them,” said Spencer Campbell, director of Plant Clinic.
Homeowners are encouraged to begin protecting their young plants as soon as possible and keep them wrapped until mid-June when emergence ends.
Can pets eat cicadas?
With millions of insects poised to invade virtually everything outside the area, some pet owners are wondering how their four-legged friends will react to the emergence of cicadas.
According to Allen Lawrance, associate curator of entomology at the Petty Notebaert Nature Museum, cicadas will be seen as a tasty treat for many animals.
“When it comes to insects, they’re very big and meaty. They have a lot of nutrients. It’s a big meal just catching an insect,” Lawrance told NBC Chicago.
Lawrence added that squirrels, birds, snakes and dogs can all be attracted to the sight of a cicada.
But are they safe for your dog?
“Yes, they are non-toxic, so they are safe for dogs to eat. However, you may need to be careful and make sure your dog doesn’t eat too much too quickly and has no stomach upset,” Lawrance said.
NBC Chicago
