Accordion List

• When will the cicadas come out?

  The 2024 emergence of 17-year periodical cicadas is likely to begin in early to mid-May (earlier in southern Illinois and later in northern Illinois). The exact timing depends on soil temperature, which depends on spring weather. The trigger is when the soil reaches 64 degrees at a depth of 8 inches. As we get closer to May, scientists may be better able to predict the day of the emergence.

• Where will the cicadas be?

  Brood XIII of 17-year cicadas will emerge in northern Illinois, southern Wisconsin, and northwest Indiana. Cicadas and trees have a long-term relationship, so the biggest crowds of cicadas will emerge in neighborhoods with many old, mature trees or in wooded natural areas. There will be few cicadas in new developments with no old trees, in dense urban neighborhoods with more paving than trees, or in places where the soil has been disturbed by construction. Cicadas evolved with native trees, such as oaks and maples, but nonnative trees can also host them.

• How long will the cicadas be here?

  The presence of cicadas will last only about four to six weeks. An individual cicada dies after three to four weeks, but there are always stragglers.

• Do periodical cicadas bite?

  No. They do not have biting mouthparts, stingers, or pincers. Their piercing-sucking mouthparts only work on trees and shrubs. Cicadas can be annoying, but they are not any danger to people or pets.

• Will cicadas attack me or my pets? Are they harmful to pets?

  No. They might accidentally blunder into you while trying to find a cicada of the opposite sex, but they are not interested in you or your pets. If a cicada lands on you, just brush it off. If you are walking in a cicada-heavy area, you might want to wear a wide-brimmed hat. Dogs and cats like to eat cicadas. The insects are edible and nontoxic. The only danger is if a pet gorges on too many cicadas and gets an upset stomach, just as it would if it ate too much of any food.

• Will they be very loud? Why?

  Yes, they will be very loud in areas where there are a lot of them. The mating call of a male cicada can sometimes be as loud as a lawnmower, and there will be millions of them. The males sing to attract females. They make the sound by vibrating drumlike structures on their abdomens to create a loud, high-pitched buzz. Each of the three local cicada species has a different call, which helps the females locate males of the right species. Only males sing; if a cicada is singing, it’s a male.

• How many cicadas will there be?

  Scientists estimate that in a forested area, there can be up to 1.5 million cicadas per acre. The density of cicadas in your neighborhood will depend mainly on how many mature trees there are. It will also depend on whether there has been development or construction since the last emergence in 2007. Cicadas spend most of their lives underground as nymphs, so construction that disturbs the soil destroys the cicada nymphs and their habitat.

• Will there be double cicadas in the Chicago area compared to the last time periodical cicadas emerged in 2007?

  No. Two synchronized periodical cicada groups, or broods, are emerging simultaneously this year. However, the broods mostly inhabit different areas of the United States. In the Chicago area, we will have about the same number of cicadas this year as we do every 17 years.

• What is special about this year?

  An unusually wide swath of the eastern United States will see an emergence of cicadas this year, although only a small area in central Illinois may actually see more cicadas than normal. This is the first year since 1803 that two broods will emerge at the same time: Brood XIII of 17-year cicadas, whose range includes the Chicago area, northern Illinois, northwestern Indiana, southern Wisconsin, and eastern Iowa, and Brood XIX of 13-year cicadas, whose range is from central Illinois south to include most of Missouri and parts of Kentucky, Tennessee, Virginia, Maryland, North Carolina, South Carolina, Georgia, Alabama, Mississippi, Louisiana and Arkansas. Since the two broods emerge at different intervals, it is rare that they coincide–only once every 221 years. Most areas, including Chicago and its suburbs, will not see more cicadas than is usual for a 17- or 13-year emergence.

• Are these the same as the cicadas I hear every August?

  No. Annual or dog-day cicadas, which you may see and hear every summer, are not the same species as periodical 17- or 13-year cicadas and are not part of the spring emergence. Annual cicadas will be present in late July and August in their usual numbers. They are often heard but rarely seen in yards and gardens.

• What does an adult periodical cicada look like?

  It is a large flying insect about 1 ½ inches long, with a black body, burnt orange to red wings with lacy veins, and bulging red eyes. Cicadas are clumsy fliers and can only fly short distances.

• Will the periodical cicadas hurt my flowers and green plants?

  No. Your garden is safe. Cicadas do not have the mouthparts required to chew leaves or stems.

• Will they hurt my trees?

  They do no serious harm to any healthy mature tree. When they first emerge, they feed briefly on the sap of woody plants, but not enough to affect a mature plant. The greatest damage they do is when female cicadas cut slits in slender twigs at the ends of tree branches and stems of some woody shrubs to create a place to lay their eggs. The twigs affected are small, between ⅛ and ⁷⁄₁₆ inches in diameter. After the eggs hatch, those twigs may die and break off. A mature tree can spare those twigs and will soon grow new ones. The only trees at risk of significant damage are very young trees that were planted within the last couple of years, or have a trunk diameter of 2 inches or less, and older trees that are unhealthy or stressed. The special organ that female cicadas use to make slits and deposit eggs is called an ovipositor and cannot pierce anything other than a twig.

• Why is the cicadas’ egg-laying potentially damaging to young trees?

  Young trees have few branches and many of them are slender twigs with thin bark that make attractive targets for female cicadas to lay eggs. A twig can be killed because a slit made by a cicada ruins too much of its living tissue. A very young tree may not have enough twigs to spare. The damage can be lasting because trees don’t heal wounds; instead, they seal them over with new wood. A twig that was slit by a cicada will grow into a branch and the tree will live with that damage for the rest of its life, even as it grows new rings of wood over the injury.

• Which tree species are most susceptible to cicada damage?

  Cicadas are not particular and will use many kinds of trees and some shrubs as hosts. However, only very young trees or older trees that are unhealthy or stressed are at any risk. The insects are known to lay eggs in oak, maple, hickory, apple, birch, dogwood, linden, willow, elm, ginkgo, and pear trees. Cicadas also may lay eggs in some shrubs, such as rose, lilac, and forsythia. They tend to avoid conifers such as pine, spruce, and fir. According to Arboretum records, during the last emergence 17 years ago some of the plants most affected were maples, cherries, ashes, hawthorns, willows, mountain ashes, oaks, pears, roses, privets, poplars, serviceberries, and beeches.

• How can I protect a young tree?

  First, make sure all your trees, old or young, are well watered and healthy, with no unaddressed disease problems. Healthy trees are always better able to withstand any pests or and diseases. For young trees, wrapping their branches in netting will keep cicadas out so they can’t lay eggs in twigs, while still allowing air and sunlight to reach the tree. Wrap the tree by early May, after leaves emerge and ideally harden off, and before the insects emerge. Keep the netting on for about six weeks, until the insects have died.

• What material should I use to wrap young trees?

  Insect netting is sold by some garden centers and many online landscape supply companies. You can also use tulle, the nylon or polyester mesh used to make ballerina tutus. The netting needs to have a fine enough mesh to keep out cicadas, with holes ¼ inch wide or less. The fabric must also be strong enough to last for several weeks on the tree. Don’t use bird netting or other mesh with holes that are ½ inch wide or more. If your little finger fits through a hole, it’s big enough to admit a cicada.

• Any tips for wrapping young trees and shrubs?

  Wrap the entire branching area of the tree. It will likely take at least several yards of fabric. Where sheets of fabric meet, overlap the edges, tuck them under once or twice, and secure the roll with binder clips, clothespins, or staples. Below the branches, gather the netting around the trunk or the base of the shrub and clip it, staple it or tie it with twine. Make sure there is no gap more than ¼ inch. Do not tie anything around the trunk so tightly that it damages the bark. Netting must stay on the tree for about six weeks, beginning in late April or early May. Be sure to remove the netting and any string or rope tied around the trunk once the cicadas have died.

• Can I use insecticides to control cicadas?

  The Arboretum does not advise that homeowners use insecticides to attempt to control cicadas. There are too many of the insects and it would be futile. Insecticides also can be harmful to beneficial insects that control other pests, leading to insect and mite outbreaks unrelated to the cicada emergence.

• Should I plant trees this spring?

  Be aware that any tree you plant this spring will be vulnerable to cicada damage. To avoid damage, you can plan to wrap the new tree in netting or wait to purchase and plant the tree until June or the fall, from the end of September through mid-October. Avoid planting trees and shrubs in July or August, when high temperatures will stress the plants.

• Can I purchase trees at the Arboretum’s Arbor Day Plant Sale in April?

  Yes. The Arbor Day Plant Sale will sell trees, April 24 through 27. Plan to plant your young trees as soon as possible after the sale and cover them with fine-mesh netting to protect them from egg-laying cicadas before the insects emerge in the middle of May. If you are not able to plant trees before mid-May, cover them in netting in their pots and keep them outside, regularly watered, until the cicadas have subsided. Netting will be sold at the sale for trees purchased there, while supplies last.

• When should I prune branches damaged by the cicadas?

  Wait until the cicadas have subsided to prune out any visible damage. It is often not necessary; dead twigs will likely fall off a tree, and larger branches are not affected. Studies have shown that most wounds left in twigs by cicadas callus over with new wood in one to two years.

• How will the Arboretum protect its trees?

  The Arboretum will use netting to cover very young trees with a trunk diameter of 2 inches or less, rare species, or young trees that have few developed branches. For these young or rare trees, staff will cover the entire tree in a tulle fabric, gathering and securing the ends to each tree’s trunk. Most larger trees can tolerate cicadas’ egg-laying. Any branches that are damaged can be pruned out, if needed, after the emergence event is complete.

• Will the cicadas be messy?

  Yes. When the cicada nymphs first emerge, they will shed their exoskeletons. After a few weeks, once they have mated and laid eggs, the insects will all die. There will be dead cicadas everywhere. You may need to clean cicadas off sidewalks and patios or out of gutters. When you are walking or driving in cicada-affected neighborhoods, take care, because crushed cicadas on pavement can be slick.

• What will the Arboretum do about dead cicadas?

  The nymph exoskeletons and the bodies of dead adults will be collected mainly in the most formal areas of the Arboretum. They will be disposed of in our compost pile, since they are rich in nutrients and minerals that improve the soil for plants. In areas where there are large numbers of cicada carcasses on hard surfaces such as roads, walks, or parking lots, they will be removed with a blower, broom, or shovel so that visitors and staff from don’t slip on them and in order to reduce the odor from the decaying insects. In places where there are not large numbers or on wood-chipped trails, the cicada remains will be left to break down naturally and enrich the soil.

• What should I do with dead cicadas at home?

  Sweep or shovel them onto your garden beds or your lawn or under trees, where they will decompose and be valuable fertilizer. They will feed soil microbes and provide nutrients such as nitrogen that encourage plants’ growth. Spread them out so they will decay more quickly. If you put cicadas in your compost, make sure they are mixed with plant matter. Turn and water the compost frequently to encourage decomposition.

• Will they stink?

  Yes. As the cicadas decay, there will be an odor of decaying cicadas for a couple of weeks.

• How can I keep flying cicadas out of my house?

  Close the windows and doors or use window screens and a screen door. Keep your car windows closed too.

• What is the insects’ life cycle?

  Eggs laid in twigs of trees or shrubs hatch into nymphs, which fall to the ground and burrow into the soil under the tree. For years, the nymphs live underground, feeding on tree roots and sap. They are active and growing, not hibernating. After 17 years (or 13 years for southern broods), the nymphs in each brood emerge from the soil all at once. Each nymph finds a vertical surface, usually a tree, where it sheds its exoskeleton and emerges as an adult cicada. The males begin singing to attract females for mating. They can fly short distances to find each other. Once the cicadas mate, about a week or 10 days after they emerge, the female finds an appropriate twig and uses an organ called an ovipositor to make a slit where she lays about 20 eggs. A single adult female cicada may lay up to 600 eggs in a number of twigs. Then all the adult cicadas die. Cicadas only live three to four weeks as adults aboveground; they spend more than 99 percent of their lives as nymphs in the soil.

• Why are the cicadas invading my neighborhood?

  They aren’t invading. They live here. Periodical cicadas are native to eastern North America and have evolved with native tree species over millions of years. They were here, mostly living underground and occasionally emerging, long before cities, suburbs, or gardens came to be.

• Why do they all come out at once?

  When millions of cicadas are all active at the same time, their many predators, such as squirrels, birds, skunks, and foxes, can’t possibly eat them all. This ensures that enough of the cicadas will escape to mate and lay eggs, continuing the species. Cicadas have no defenses except their sheer number: They are slow, clumsy fliers that do not sting, bite, or hide. Scientists call this kind of survival strategy “predator satiation.” It’s similar to a mast year of oak trees, when there is a huge crop of acorns–too many for squirrels and blue jays to eat them all.

• How do they know when 17 years have passed and it’s time to emerge?

  Scientists still aren’t sure. However, it’s believed that the underground nymphs have an internal molecular clock that may track the yearly life cycle of the trees they live with. They may respond to chemical changes in the root sap they feed on.

• Since cicadas are native and have evolved with our plants, what kind of defenses have our native plants developed to protect themselves?

  Some woody plants have probably developed thicker bark at a younger age. They likely have also developed mechanisms to seal off or compartmentalize the damage more efficiently to prevent decay from entering the tree.

• How do the cicadas affect wildlife?

  A cicada emergence is a bonanza for animals. You may see many kinds of animals feeding on them, including squirrels, raccoons, skunks, foxes, coyotes, and dozens of bird species. The feeding frenzy can have complicated ripple effects on the local ecosystem. For example, with an ample food supply, more songbird hatchlings survive, so populations of some bird species increase. At the same time, birds that have plenty of cicadas to eat may not bother to eat caterpillars of other insect species, allowing more of those insects to survive. Foxes and coyotes that fill up on cicadas may not hunt other prey, leading to an abundance of rabbits. Meanwhile, the blast of fertilizer from the decay of the cicadas causes a burst of tree and plant growth the next year.

• How are Arboretum experts studying cicadas?

  Our scientists are studying the short- and long-term effects of cicadas on soil and trees. They’re specifically focused on dead cicadas. Much like leaf litter, cicadas are rich in nutrients, and after they die, they decompose and add a pulse of nutrients to the soil. Scientists will weigh dead cicadas and measure nutrient content. They will then measure the resulting soil nutrient concentrations. Our science team will also be tracking tree growth this year and beyond to determine how the cicada nutrient pulse has impacted tree growth. Additionally, Arboretum experts are asking: which trees are cicadas most attracted to? Do we find them to be more or less abundant in evergreen or deciduous forests?

• Should we be alarmed by cicadas?

  No. They may be weird and annoying, but they are harmless to people and pets. Their emergence is a fascinating natural phenomenon that we only get to see every 17 years. It still has many mysteries for scientists. Periodical cicadas are so amazing that their scientific genus name is Magicicada. There are three species in Brood XIII: Magicicada septendecim, Magicicada cassini, and Magicicada septendecula, each with a different mating call.

• Are cicadas edible?

  Yes. People can eat them just like raccoons can. You can find recipes for cicadas on the internet.