Every 17 years, a remarkable natural event unfolds across parts of the United States—the emergence of the 17-year cicadas. These periodical insects, known scientifically as Magicicada, remain hidden underground for over a decade and a half before emerging en masse in a synchronized and often mind-boggling display. Their appearance isn’t just a curiosity for nature enthusiasts; it’s an ecological phenomenon with wide-reaching impacts. In this in-depth article, we’ll explore where these 17-year cicadas are expected to emerge, understand why their timing is so precise, examine the species involved, and offer insights into how communities can prepare for the emergence.
The Life Cycle of 17-Year Cicadas
Before we dive into the geographic specifics, it’s crucial to understand what makes 17-year cicadas so unique.
Years Underground: The Nymph Stage
17-year cicadas spend the vast majority of their lives in the nymph stage, buried beneath the soil. After hatching from eggs laid in tree branches, the tiny nymphs fall to the ground and burrow into the earth. They latch onto tree roots and feed on sap, slowly growing through several molts over the next 17 years. This subterranean phase is one of the longest developmental cycles of any insect in the world.
Mass Synchronous Emergence
What truly sets periodical cicadas apart is their ability to emerge from the ground all at once, triggered by soil temperature and a biological clock fine-tuned over centuries. When the soil approximately 8 inches deep reaches about 64°F (18°C), the cicadas begin tunneling upward. They emerge, climb trees or other vertical surfaces, and molt into adults—shedding their exoskeletons to reveal translucent wings and red eyes.
This mass emergence is both a defense mechanism and a reproductive strategy. By emerging in overwhelming numbers, cicadas ensure that predators can’t possibly consume them all, increasing the chance that enough survivors will mate and lay eggs to continue the species.
Broad Geographic Range of 17-Year Cicadas
The 17-year cicadas are native to the eastern United States and are not uniformly distributed. Their presence is broken into distinct populations called broods, each with their own geographic range and emergence schedule. These broods are numbered and tracked by scientists to predict emergence patterns.
What Are Broods?
A “brood” refers to a specific population of periodical cicadas that emerge together in a synchronized 17-year cycle. There are 12 known broods of 17-year cicadas, designated as Brood I through Brood X, Brood XIII, and Brood XIV (some historically documented broods have gone extinct). These broods are separated geographically and may not emerge simultaneously. For instance, Brood X appears every 17 years in parts of the Midwest and Mid-Atlantic, while Brood XIII emerges in Illinois and surrounding areas.
Recent and Upcoming Emergences: Brood XIII in 2024
In 2024, one of the most significant insect events in the U.S. took place: the emergence of Brood XIII, also known as the “Great Northern Brood.” This brood primarily inhabited parts of northern Illinois, with sightings also reported in southwest Wisconsin, northwest Indiana, and possibly very small areas of lower Michigan.
The 2024 emergence of Brood XIII was especially notable because it overlapped in time with the emergence of Brood XIX, a 13-year cicada brood. This rare coincidence—called a “double emergence”—only occurs in a few areas and creates an even louder and more visible cicada presence.
Predicting Future Emergences
Given the precise cycling, scientists can project where 17-year cicadas will next emerge. Here is a table illustrating the next few 17-year cicada broods and their expected emergence years:
| Brood Number | Common Name | Expected Emergence Year | Primary States |
|---|---|---|---|
| Brood I | Virginia-West Virginia Brood | 2026 | Virginia, West Virginia |
| Brood II | East Coast Brood | 2027 | New York, Connecticut, New Jersey, North Carolina |
| Brood III | Iowa Brood | 2028 | Iowa, Illinois (small areas) |
| Brood IV | Kansan Brood | 2029 | Kansas, Oklahoma, Missouri |
| Brood VI | North Carolina-Georgia Brood | 2030 | North Carolina, Georgia, South Carolina |
Note that emerging cicadas typically appear between late May and early July, depending on local soil conditions and spring temperatures.
States Where 17-Year Cicadas Are Currently Found
While different broods emerge in different years, the core distribution of 17-year cicadas spans a broad swath across the eastern United States. The most commonly affected states include:
- Illinois: Especially during Brood XIII (2024) and Brood XIII-related overlaps.
- Indiana: Northern and central regions see significant emergences.
- Ohio: Regularly impacted by Brood V and Brood X events.
- Pennsylvania: A key state for Brood X, with heavy emergences in suburbs of cities like Philadelphia.
- New York and Connecticut: These Northeastern states are home to Brood II, with notable activity in the Hudson Valley and Long Island.
- West Virginia and Virginia: Central to Brood I’s territory, which will emerge in 2026.
- Wisconsin and Michigan: Northern counties may see Brood XIII spillover.
- Tennessee and North Carolina: Home to multiple broods, including 13-year and some 17-year varieties.
It’s important to remember that not every county within these states sees emergences. The insects are localized to areas with the right soil composition, tree density, and historical brood territory. Urban sprawl and deforestation have reduced habitat in some areas, leading to patchy or diminished appearances.
Why Do 17-Year Cicadas Emerge in Specific Locations?
The emergence of cicadas isn’t random—it’s the result of evolutionary adaptation, environmental conditions, and genetic programming.
Soil Conditions and Tree Roots
Cicada nymphs depend on tree roots for nourishment. They thrive in areas with deciduous forests or suburban landscapes with established trees such as oak, maple, ash, and willow. The soil must be well-drained but retain enough moisture to support nymph development. Areas with clay-heavy or compacted soils may support fewer cicadas.
Geographical Isolation and Brood Boundaries
Over time, natural barriers such as rivers, mountain ranges, and human development have helped isolate brood populations. For example, the Mississippi River serves as a partial boundary between Brood IV (Great Plains brood) and eastern broods like Brood X. While some migration might occur over centuries, most broods remain confined to their ancestral zones.
The 17-Year Cycle: Evolutionary Advantage
The 17-year development cycle is believed to be an evolutionary strategy. Because 17 is a prime number, it’s less likely that predators with shorter life cycles (e.g., every 2 or 4 years) will synchronize with the cicadas. This reduces the chances of sustained predation pressure over time. This unique timing, combined with the sheer volume of emerging insects, maximizes survival through predator satiation.
Key Cities and Regions to Watch
If you’re planning travel, gardening, or simply want to witness the spectacle, knowing exactly where cicadas might appear in your region can be helpful.
Midwest: Chicago, IL – Heart of Brood XIII
In 2024, the Chicago metropolitan area became a hotspot for Brood XIII cicadas. Suburbs like Naperville, Evanston, and Schaumburg reported massive emergences, particularly in parks, forest preserves, and yards with mature trees. The annual event at the Morton Arboretum even hosted “Cicada Fest” to celebrate and educate the public.
Chicago’s role in Brood XIII is significant because it’s one of the few major cities in the natural range of this brood. Residents were treated—and sometimes tormented—to a soundtrack of cicada songs peaking at over 100 decibels in some areas.
Mid-Atlantic: Washington D.C., Philadelphia, and Cincinnati in Brood X Years
Brood X, known as the “Great Eastern Brood,” is one of the largest and most widespread 17-year cicada groups. It last emerged in 2021 and will next appear in 2038. During its emergence, residents of:
- Washington D.C.: Rock Creek Park and nearby forests buzzed with cicadas.
- Philadelphia, PA: Large numbers appeared in Fairmount Park and the Wissahickon Valley.
- Cincinnati, OH: Suburbs with older neighborhoods saw heavy tree infestations.
This brood draws national attention because of its reach into major urban centers and the media coverage it generates.
Southern and Appalachian Region: Preparing for Brood I (2026)
Coming up in 2026, Brood I will reawaken in southwestern Virginia and parts of eastern West Virginia. Cities like Roanoke, VA, and Beckley, WV, can expect cicada activity in wooded residential areas. Though not as densely populated as earlier broods, Brood I holds historical significance—it has been documented for centuries by naturalists.
Local governments in these regions often begin outreach programs in advance, educating homeowners about protecting young trees and understanding cicada behavior.
How to Identify 17-Year Cicadas vs. Annual Cicadas
Many people confuse periodical 17-year cicadas with annual or “dog-day” cicadas that appear every summer. However, several features set them apart.
Physical Characteristics
- Eyes: 17-year cicadas have bright red or orange eyes.
- Wings: Their wings have orange veins and are held roof-like over the body.
- Size: Slightly smaller than annual cicadas, typically about 1.25 inches long.
- Coloration: Black bodies with red or orange markings on the legs and underside.
Annual cicadas, such as the Neotibicen species, are typically larger, greenish or brownish, and appear solo or in small numbers throughout late summer.
Behavior and Sound
17-year cicadas are far more vocal and synchronized. Males gather in trees and produce loud, pulsing mating calls to attract females. The collective sound can reach deafening levels—comparable to a lawn mower or subway train. The calls of periodical cicadas are distinct and species-specific, with each of the three main periodical species in a brood having its own call.
Impact on Trees and Gardens
While cicadas don’t bite humans or spread disease, their egg-laying habits can harm young trees and shrubs.
Egg-Laying and Branch Damage
Female cicadas use a sharp ovipositor to slice into small tree branches (usually ¼ to ½ inch in diameter) and lay their eggs in these slits. This process, called “flagging,” causes the tips of branches to wilt and die, creating a striped pattern on the foliage. While mature trees can withstand this damage, saplings and young ornamental trees (like fruit trees or Japanese maples) are vulnerable.
Homeowners with young trees or new plantings are advised to use fine mesh netting (with holes smaller than 0.5 cm) to protect vulnerable trees. Avoid using pesticides, as they are largely ineffective against cicadas and can harm beneficial insects such as bees.
Benefits to the Ecosystem
Despite the nuisance factor, cicadas play a vital ecological role:
- They aerate soil during emergence.
- They provide a massive food source for birds, mammals, and other insects.
- When they die, their decomposing bodies enrich the soil with nitrogen, benefiting plant growth.
Some scientists even refer to cicada emergences as “pulse events” that boost forest productivity in the years that follow.
How Communities Can Prepare
With cicadas emerging in predictable patterns, local governments, schools, and gardening associations often implement education and protection strategies.
Public Education Campaigns
Many municipalities and extension services (such as those from land-grant universities) release guides on cicada behavior, safety, and tree protection. For example, the University of Illinois Extension offered resources on managing emergences in 2024, including identification tools and DIY tree wrap instructions.
Timing Outdoor Events
Because cicadas are most active during the day and peak in early summer, event planners may choose to schedule weddings, outdoor parties, or public gatherings later in June or July—after the initial wave of molting and mating subsides.
Urban Planning Considerations
Long-term urban planners now consider cicada brood maps when planting new trees or redesigning parks. Delaying the planting of young trees in high-risk areas until after an emergence year can prevent long-term damage.
What Does the Future Hold for 17-Year Cicadas?
As climate change alters temperature and precipitation patterns, cicada emergence behavior is under scientific scrutiny.
Potential Shifts in Emergence Timing
Warmer springs may cause earlier emergences. There’s already evidence of some cicadas emerging a year early or late—a phenomenon called “straggling.” While occasional stragglers are normal, increasing frequency could disrupt the synchronization that ensures their survival.
Habitat Loss and Urbanization
Urban development reduces suitable habitat for nymphs. Concrete, lawns, and shallow-rooted plants don’t support long-term underground development. As cities grow, some broods may shrink or disappear entirely. Brood XI, once present in Connecticut, has not been seen since the 1950s and is considered extinct.
Climate Resilience of Broods
Interestingly, genetic studies suggest that periodical cicadas are resilient and have survived multiple glacial cycles. Their prime-numbered life cycles may provide a buffer against rapid environmental changes. However, the pace of modern climate shift and habitat fragmentation poses unprecedented challenges.
Witnessing a Natural Wonder
For those fortunate enough to experience a 17-year cicada emergence, it’s more than an annoyance—it’s a **natural wonder**. Few other insect events match the scale, precision, and raw power of a full brood emergence.
Whether you’re a homeowner bracing for tree damage, a teacher planning a biology lesson, or a nature lover eager to hear the “song of the earth,” understanding where these cicadas appear—and why—deepens our appreciation for their role in the ecosystem.
Keep an eye on the calendar. Mark your brood emergence years. And next time the ground starts to hum in late spring, remember: you’re not just hearing insects—you’re witnessing a cycle millions of years in the making.
Where will the 17-year cicadas emerge in 2024?
The 17-year cicadas, specifically Brood XIII (also known as the Great Northern Brood), are expected to emerge primarily in northern Illinois, with sightings also anticipated in parts of northwest Indiana and southern Wisconsin. These areas provide the ideal soil conditions and temperature cues that trigger the cicadas’ synchronized emergence after 17 years underground. Urban and suburban regions, including Chicago and its surrounding suburbs, may experience particularly noticeable populations due to the abundance of mature trees that support nymph development.
This massive emergence will be most intense from late May through late June, depending on local weather patterns. Soil temperatures reaching approximately 64°F (18°C) at a depth of about 8 inches act as the biological trigger for nymphs to crawl to the surface. While focused on specific states, occasional sightings may occur in neighboring regions due to migration or minor population spread. Residents in these areas should expect a loud and temporary natural spectacle, with billions of cicadas emerging almost simultaneously.
What causes 17-year cicadas to emerge after so long?
The emergence of 17-year cicadas is driven by a biological clock synchronized with soil temperature and tree root signals. After hatching, cicada nymphs burrow underground, where they feed on xylem sap from tree roots. During their 17-year life cycle, they undergo several molts, gradually maturing. Scientists believe that the nymphs track the passage of time by monitoring subtle, annual changes in the nutrient flow of the roots, which helps them identify when 17 growing seasons have passed.
When the soil warms to about 64°F at the appropriate depth—typically in late spring—the nymphs instinctively begin to emerge. This precise timing ensures that the entire brood surfaces within a short window, maximizing mating success through sheer numbers. Known as predator satiation, this strategy overwhelms birds, mammals, and other predators, allowing a large portion of the population to survive long enough to reproduce. The coordinated emergence is one of nature’s most remarkable examples of synchronized life cycles.
Are 17-year cicadas harmful to humans or pets?
No, 17-year cicadas are not harmful to humans. They do not bite or sting aggressively, and they lack the mouthparts necessary for biting through human skin. Occasionally, a cicada might land on a person and try to probe the skin, mistaking it for a plant, but this is harmless and rarely felt. Additionally, cicadas are not poisonous, and their presence poses no health risk to people, including children or those with allergies.
Pets may show curiosity toward cicadas, especially dogs that might eat them in large quantities. While cicadas are not toxic to animals, consuming too many can cause gastrointestinal upset, including vomiting or diarrhea, due to their hard exoskeletons. It’s advisable to monitor pets during the emergence and discourage excessive eating. Overall, cicadas are considered a nuisance but not a danger, and they actually provide a temporary food source for wildlife such as birds, squirrels, and reptiles.
How long will the cicada emergence last?
The 17-year cicada emergence typically lasts four to six weeks from the initial appearance of nymphs to the death of the final adults. The peak period, when most cicadas are active, mating, and producing their loud calls, generally occurs within the first three weeks of June. During this time, the forested and suburban landscapes in affected regions may be filled with an intense, continuous buzzing sound produced by male cicadas to attract mates.
After mating, female cicadas lay eggs in tree twigs by making small slits, a process that can cause minor damage to young branches. The adult cicadas die shortly afterward, usually by early July. The eggs hatch about six to ten weeks later, and the nymphs drop to the ground and burrow into the soil to begin their 17-year development cycle. While the adult phase is brief, it marks the culmination of a long, subterranean journey and plays a vital role in forest ecology.
Can 17-year cicadas damage trees and plants?
While 17-year cicadas are not feeding pests like aphids or caterpillars, female cicadas can cause some injury to young trees and shrubs during egg-laying. Using a sharp ovipositor, they slice thin branches—typically pencil-sized twigs—to deposit their eggs. This process, called flagging, can result in the tips of branches wilting, browning, or breaking off due to disrupted sap flow. Orchards, nurseries, and newly planted trees are most vulnerable to this type of damage.
Healthy, mature trees generally tolerate cicada egg-laying without long-term harm. However, for young or valuable saplings, protective measures such as covering them with fine netting (with mesh smaller than 1/4 inch) can prevent females from accessing the branches. Avoiding pruning during the emergence period can also help by preserving existing healthy tissue. Overall, cicada presence benefits ecosystems by aerating soil, providing nutrients as their bodies decompose, and serving as food for numerous species.
Why are there different broods of 17-year cicadas?
The existence of different broods allows for geographic and temporal separation among 17-year cicada populations, reducing competition and increasing survival rates. There are 12 known broods of 17-year cicadas, each with a distinct emergence schedule and location across the eastern United States. These broods are essentially separate generations that developed different internal timing mechanisms, allowing them to emerge in a staggered pattern every year in various regions, even though each individual brood appears only once every 17 years.
For example, Brood X emerged in 2021 across several Mid-Atlantic states, while Brood XIII is scheduled for 2024 in the Midwest. This intricate system minimizes overlap between broods and prevents overcrowding in any one area. The brood structure has likely evolved over millennia to maintain genetic diversity and ensure that cicadas do not face excessive environmental pressures all at once. This organization makes long-term cicada observation and scientific study more manageable.
What can people do to enjoy or document the cicada emergence?
The 17-year cicada emergence offers a rare opportunity for nature observation, photography, and citizen science. People can track cicada sightings by using mobile apps like iNaturalist or Cicada Safari, which allow users to upload photos and location data, helping researchers map emergence patterns in real time. Educators and families can use this event to teach children about insect life cycles, ecosystems, and natural timing mechanisms.
While some may find the noise and abundance off-putting, many embrace it as a temporary natural wonder. Taking photos, recording their distinctive calls, or simply watching their behavior can be both educational and entertaining. Additionally, avoiding the use of pesticides is recommended, as cicadas are not harmful and their presence benefits local wildlife. Communities that acknowledge the emergence as a unique ecological event often host educational events or cicada-themed activities to celebrate this remarkable phenomenon.