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What you need to know about the much-hyped 2024 cicada emergence
| Story by Meghan McMahon |
5/1/2024
More than 3,000 species of cicadas exist in the world, but it’s just a handful of them that will be making headlines in Illinois this summer. After 17 years, the brood of periodical cicadas that lives in northern Illinois will be emerging to much fanfare.
We can expect the buzz — both literal and figurative — to begin sometime in May. You might have some questions about this newsworthy occasion. Lucky for you we have answers.
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Periodical cicadas only emerge every 13 or 17 years, so it’s always noteworthy when they do. But the emergence in Illinois this year has an added level of significance because something is about to happen that hasn’t happened since 1803.
This year, two broods of cicadas will emerge in Illinois. One brood, Brood XIII, or the Northern Illinois Brood, is 17-year cicadas. The other, Brood XIX, or the Great Southern Brood, is 13-year cicadas, according to the University of Illinois Extension. Because the two broods of cicadas have different life cycles, they only emerge in the same year every 221 years. After this year, it won’t happen again until 2245.
What does it all mean? A whole lot of cicadas — billions or even trillions of them — coming up from underground in Illinois this year. But because the ranges for the two broods of cicadas don’t overlap, it doesn’t mean more cicadas in any one place, it simply means more of Illinois will experience a cicada emergence this year, the extension reports.
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In Illinois, periodical cicadas typically begin emerging from underground in late May or early June. Once the soil temperature reaches 64 degrees Fahrenheit at a depth of 8 inches below ground, they will start emerging, according to the University of Illinois Extension.
We won’t start hearing them right away. Only the males sing, and they usually start singing their familiar song four or five days after making their way aboveground. Once they get started, we usually hear them for about four to six weeks.
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Although billions of these insects will be emerging from underground in northern Illinois, we won’t see them just everywhere. Cicadas require trees to complete their life cycle — they eat tree material both aboveground and belowground and also lay their eggs in trees — so we will generally hear them only in areas with trees, the Purdue University Extension reports.
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Not just any old trees will do. They have to be mature trees. Remember, they have been underground for 17 years. If your yard didn’t have trees in it 17 years ago, the cicadas that will emerge this year can’t have been hanging around underground long enough to be in your yard. Even if your yard did have trees 17 years ago you might not get cicadas because the trees have to have been mature and must have been continually present.
We will generally see and hear cicadas in areas like forests, preserves and parks that have had mature tree cover for more than 17 years. If you heard cicadas in your yard or neighborhood when they emerged in 2007, it’s safe to count on it again as long as trees are still standing and the soil hasn’t been disturbed by construction.
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Suffice it to say there will be a lot of cicadas emerging in the Chicago area, but exactly how many is difficult to quantify because it can fluctuate from emergence to emergence. Billions or even trillions is a safe bet because scientists estimate they can reach a density of 1.5 million cicadas per acre, the Morton Arboretum reports.
Cicada density will be greatest in areas that have a lot of mature trees and that have been undisturbed since the 2007 emergence. Land that has been the site of construction or development since 2007 may see fewer or no cicadas this year even if they were present in the last emergence.
Once aboveground, cicadas don’t travel far from where they emerged, usually no more than half a mile, according to the Illinois Extension. Because of this, their range has not expanded much even over the course of the past few centuries. In the time since Abraham Lincoln was president, our Northern Illinois Brood has emerged nine times, but their range has probably expanded no more than 5 miles over that span.
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Our periodical cicadas spend 17 years underground, so why come aboveground anyway? They emerge for just one reason: to mate. The males sing their buzzing song to attract a female mate.
Once they mate, the females will lay their eggs in trees, according to the National Museum of Natural History. The females create slits in twigs that are about the size of a pencil and then lay their eggs inside. The eggs hatch after about six or seven weeks, but by then their parents are already gone. The adult cicadas only live for about three or four weeks after emerging.
The newly hatched nymphs will drop from the trees where they hatched and then burrow down into the soil, the museum reports. There they will stay for 17 years — until 2041 in our case here in northern Illinois. They aren’t dormant underground. They tunnel through the soil for all their subterranean years, feeding on tree roots as they do.
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With all the headlines about the coming cicada emergence, the big question for many people will be how loud is it going to get. Well, you might want to get some earplugs. The buzzing chorus of cicadas can reach about 100 decibels, which is about as loud as a chainsaw from 3 feet away, Smithsonian Magazine reports.
It’s not just that the cicadas are noisy, it’s that the noise is sustained, with the call lasting for hours a day for a period of several weeks. But it could be worse. Only the males sing. Can you imagine the racket if all the cicadas that emerge were singing for hours a day for several weeks?
The males sing to attract a mate. To create their song, they have a pair of structures called tymbals on their abdomens behind their last pair of legs, according to the Missouri Department of Conservation. The tymbals have a series of ribs, and when the bugs flex their muscles, it creates a clicking sound. That clicking sound is the song we are about to become so familiar with.
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Not at all. Cicadas don’t bite or sting, and they aren’t poisonous, according to the Purdue University Extension. They are even safe to eat if handled and prepared properly.
About the only potential risk from cicadas is to young or small trees, according to the Morton Arboretum. Female cicadas create slits in twigs and then lay their eggs in them. If large numbers of cicadas do this on young trees, all those twigs can break off and die once the eggs hatch, causing lasting damage. However, only young trees or trees with a trunk diameter of 2 inches or less are at risk. To protect your young trees, the arboretum suggests wrapping their branches in netting made from fine mesh before the emergence begins.
The biggest issue with the cicada emergence is that it can be a nuisance. It’s loud, and in some places carcasses from the insects can begin to pile up as they begin to die off, the Illinois Extension reports. The smell of the piles of dead insects can be a little off-putting, similar to roadkill or other decaying animal flesh.
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Most insects don’t live very long. Houseflies live about 28 days. Most monarchs butterflies live two to six weeks, although the monarchs that migrate at the end of summer can live as long as nine months. Lady bugs can live as long as two or three years. So the 13- and 17-year life cycles of periodical cicadas are quite remarkable. They are actually one of the longest living insects in the world, the Illinois Extension reports.
Scientists don’t fully understand why cicadas have such long life cycles compared to most insects. One theory is it is because they evolved over the course of ice ages and the cold temperatures during these eras caused them to grow more slowly, which allowed them to live longer, the Illinois extension reports. It is thought that they synchronized their life cycles to emerge at once so they could more easily find mates to reproduce.
It has also been theorized that their long life cycles make it difficult for predators to sync up with them. Plus their mass emergences overwhelm predators, making it more likely they will successfully reproduce rather than being predated by other wildlife.
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Periodical cicadas are large by insect standards. They are about 1 inch long, and their wingspan is about 3 inches, according to the National Wildlife Federation. They are dark in color, black from above and orange from below. Their most notable features are their wings and eyes, both of which includes flashes of color. Their eyes are bright red, and their lacy wings appear golden or orange in color.
Cicadas typically emerge in the evening, and when they first emerge they may look a little different than what you are used to. When they first emerge, the cicadas are white in color and have soft bodies, according to the Illinois Extension. Overnight, their bodies will harden and they will become dark in color.
You can tell the difference between periodical and annual cicadas based on their size and color. Annual cicadas are larger than periodical cicadas, about 1½ inches to 2½ inches long, according to the Illinois Extension. From above, annual cicadas are mostly dark with a green pattern. Their eyes are dark in color. From underneath, annual cicadas are white.
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Periodical cicadas only emerge every 13 or 17 years, but there is another type of cicada — annual cicadas — that we hear from much more frequently, every summer in fact. Annual cicadas, also called dog-day cicadas, also have life cycles that last multiple years — typically between two to eight years depending on the particular species — but their life cycles are not synchronized, so some emerge each year rather than all in the same year, making their arrival less notable, according to the University of Illinois Extension.
Annual cicadas emerge later in the year than periodical cicadas, so we will get a break — albeit a short one — between hearing the periodical cicadas and annual cicadas. The chorus created by periodical cicadas will likely wind down in June, and the annual cicadas usually don’t start singing until the dog days of summer, which is why they are also called dog-day cicadas, according to the Illinois Extension. The dog days of summer are generally considered to be from July 3 to Aug. 11.
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