Periodical cicadas, the famous insects that emerge in synchronized masses every 13 or 17 years, live exclusively in the eastern half of the United States. Their range spans roughly 30 states, from as far north as New York and Wisconsin down through Georgia, Mississippi, and eastern Texas. But “cicadas” more broadly, meaning the annual species that show up every summer, live in all 50 states. The distinction matters because when most people ask about cicada states, they are really asking about the periodical broods that make national news, and the answer to why those insects live where they do involves glacial history, deciduous forests, and a survival strategy that only works when billions of them show up at once.
Where Periodical Cicadas Actually Live
Periodical cicadas belong to the genus Magicicada, and they are found nowhere else on Earth outside the eastern United States. Their range stretches from the Atlantic seaboard west to roughly the Great Plains, and from the upper Midwest south to the Gulf states. The states with the densest and most well-documented populations include Ohio, Indiana, Illinois, Pennsylvania, Virginia, West Virginia, Maryland, Tennessee, Kentucky, and North Carolina. But broods also extend into Connecticut, New Jersey, New York, Michigan, Wisconsin, Iowa, Missouri, Arkansas, Oklahoma, Kansas, Georgia, Alabama, Mississippi, Louisiana, South Carolina, and parts of eastern Texas.
These insects are organized into broods, each designated by a Roman numeral. There are currently 12 active broods of 17-year cicadas and three active broods of 13-year cicadas. Each brood occupies its own geographic footprint that can cover several states or just small pockets within a few counties. Brood X, for instance, one of the largest, spans portions of about 15 states from New Jersey to Indiana and down through parts of Georgia. Brood XIX, the largest 13-year brood, covers a swath of the Southeast and Midwest. Not every state in the range will see cicadas in any given emergence year, because different broods emerge on different schedules and in different places.
The geographic split between 13-year and 17-year species roughly follows a climatic line. Seventeen-year cicadas dominate the northern part of the range, while 13-year cicadas are concentrated in the South and lower Midwest. There is a contact zone through states like Illinois, Indiana, Missouri, and Arkansas where both life-cycle types coexist, sometimes even in overlapping territory.
Why the Eastern United States and Nowhere Else
The question of why periodical cicadas are restricted to the eastern half of the country is fundamentally a question about forests and ice ages. Periodical cicadas depend on deciduous hardwood trees. The nymphs spend their entire underground development feeding on the xylem fluid of tree roots, which means they need well-established trees with extensive root systems in soils that stay moist enough to support over a decade of subterranean life. The mixed hardwood forests of the eastern United States provide exactly that habitat.
Glacial history shaped the boundaries. During the Pleistocene ice ages, glaciers covered much of the northern United States and pushed temperate forests south. When the ice retreated, the forests slowly expanded northward again, and the cicadas followed. Genetic evidence shows that the earliest split among the three surviving Magicicada species groups happened around four million years ago, with further diversification occurring around 2.5 million years ago. But the split between 13-year and 17-year life cycles within any single species group is far more recent. In the Decim lineage, for example, 13-year and 17-year populations diverged only about half a million years ago, and all three species groups experienced additional life-cycle changes since the last glacial maximum roughly 20,000 years ago.1PubMed Central. Independent divergence of 13- and 17-y life cycles among three periodical cicada lineages
Researchers have hypothesized that when populations that had been separated by glacial barriers came back into contact, the invading group synchronized its life cycle to match the dominant local population. This synchronization would have helped the newcomers benefit from the safety-in-numbers strategy that periodical cicadas depend on. That process of matching cycles and merging into existing broods helps explain how the three species groups ended up with overlapping geographic distributions today, despite having evolved independently.1PubMed Central. Independent divergence of 13- and 17-y life cycles among three periodical cicada lineages
West of the Great Plains, the landscape transitions to grasslands and drier climates that lack the continuous canopy of deciduous hardwoods that cicada nymphs need. The Rocky Mountains and arid Southwest are inhospitable for the same reasons. It is not that cicadas could not physically survive there in some abstract sense; it is that the specific ecological foundation they require, deep-rooted deciduous trees in moist, temperate soils, simply does not exist in those regions.
Annual Cicadas Are a Different Story
If you have heard cicadas buzzing on a hot summer afternoon, you have almost certainly heard an annual species rather than a periodical one. Annual cicadas, sometimes called dog-day cicadas because they tend to appear in the hottest weeks of summer, belong to genera like Neotibicen and Megatibicen. They are found across the entire continental United States, including the West Coast, the Southwest, and even Hawaii. Some species thrive in arid environments, and others are common in suburban yards with a single shade tree.
Annual cicadas still spend multiple years underground as nymphs, typically two to five years depending on the species, but their generations overlap so that adults appear every summer. There is no synchronized mass emergence, no brood numbering system, and no national news coverage. They emerge individually or in modest numbers, sing their mating calls, reproduce, and die without the spectacle that Magicicada creates.
So if you live in Oregon, Arizona, California, or any state west of the Plains and have heard a loud insect drone in the trees during summer, those are your local annual cicadas. They are just not the periodical kind that prompts “what states have cicadas” as a search query.
How Nymphs Survive Underground for Over a Decade
A periodical cicada nymph hatches from an egg laid in a tree branch, drops to the ground, burrows into the soil, and then stays there for 13 or 17 years. During that entire time, it feeds by tapping into the xylem vessels of tree roots and drinking the fluid that flows through them. Xylem fluid is the water-and-mineral stream that trees pull up from the soil. It is extraordinarily dilute compared to other plant fluids, containing only trace amounts of amino acids and sugars. That extreme dilution is probably a big part of why periodical cicadas take so long to mature: growing to adult size on such a thin nutritional resource simply takes many years.2Ecological Entomology. Xylem feeding by periodical cicada nymphs on tree roots
This feeding habit also means the nymphs are tied to areas with healthy, established trees. Young saplings or sparse root systems would not sustain a nymph for 17 years. The deep, well-watered soils under mature eastern hardwood forests are ideal. In areas where forests have been cleared for agriculture or development and not replaced with trees, local cicada populations can quietly die out underground without anyone noticing until the next emergence year comes and nothing shows up.
One of the more remarkable findings about periodical cicadas is how they keep track of time underground. Researchers experimentally manipulated the seasonal cycles of trees supporting nymphs, essentially giving the trees an extra “year” by forcing them through an additional cycle of leafing out and going dormant. The cicadas responded by emerging a year early, proving that they count the annual cycles of their host tree rather than tracking real calendar time or accumulating temperature.3Ecology Letters. How 17‐year cicadas keep track of time The nymph essentially uses the tree as a clock, ticking off each spring flush of growth as one year until it reaches 13 or 17.
Why Oak Trees Matter So Much
Not all trees are equal in a periodical cicada’s world. Research in Appalachian forests has shown that oak trees (Quercus species) are far and away the most important hosts. More emergence holes were found beneath oaks than any other tree genus. Adult cicadas preferentially gathered on oaks for their chorusing centers, the areas where males sing to attract females. And females laid more egg bundles in oak branches than in other species. Even in controlled experiments testing nymph preferences, nymphs were more attracted to oak roots than to maple roots.4Journal of Forestry Research. Use of tree species by three species of Magicicada (Hemiptera: Cicadidae) in an Appalachian forest
This preference for oaks further explains the geographic distribution. The eastern United States is the global center of oak diversity, with dozens of species forming a major component of forests from New England to the Gulf Coast. Where oaks thrive, cicadas tend to thrive. The three Magicicada species in any given brood do show some differences in which specific tree species and sizes they prefer, which may help them partition resources and reduce competition with one another during the crowded weeks of an emergence.4Journal of Forestry Research. Use of tree species by three species of Magicicada (Hemiptera: Cicadidae) in an Appalachian forest
For homeowners with young trees, the practical concern is egg-laying damage. Females use a saw-like ovipositor to slice slits into branches and deposit eggs. The branch diameter matters more than anything: branches roughly 5 to 10 millimeters in diameter are the sweet spot for egg-laying, while thicker or thinner branches are less suitable. Young trees whose main trunk or scaffold branches fall in that size range can suffer serious breakage and growth loss. Larger, established trees experience only minor natural pruning from the same process.5Arboriculture & Urban Forestry. Effects and Control of Periodical Cicada Magicicada septendecim and Magicicada cassini Oviposition Injury on Urban Forest Trees
Safety in Numbers and Why Small Populations Disappear
The defining survival strategy of periodical cicadas is predator satiation. Billions of insects emerge within the span of a few days across a region, and the sheer volume overwhelms every predator in the area. Birds, squirrels, dogs, fish, and even curious humans eat cicadas in abundance, but there are simply too many to make a dent. Research on 13-year cicadas found that birds consumed between 15 and 40 percent of the standing crop in areas with low cicada density, but at high densities, above about 24,000 individuals per hectare, bird predation barely registered. Across the most active emergence areas, birds consumed only around 15 percent of the total adult population.6Ecology. Emergence of 13‐Yr Periodical Cicadas (Cicadidae: Magicicada): Phenology, Mortality, and Predators Satiation
The timing worked in the cicadas’ favor too. The earliest adults to emerge in early May were heavily eaten by birds, but avian predators became satiated within days. By the time the birds’ food demands ramped up again weeks later, when they had nestlings to feed, the density of adult cicadas had already declined naturally.6Ecology. Emergence of 13‐Yr Periodical Cicadas (Cicadidae: Magicicada): Phenology, Mortality, and Predators Satiation
This strategy has a dark flip side. It only works when density is high. A cicada population that has been thinned out, whether by habitat loss, forest fragmentation, or just bad luck over multiple cycles, can fall below the density threshold where predator satiation kicks in. At that point, birds and other predators can eat a devastating proportion of the emerging adults, reducing the next generation further. Researchers have observed that at low densities, cicadas even experience higher rates of failed molts, the final shedding of the nymphal skin that happens as they emerge from the ground.7The Great Lakes Entomologist. Periodical cicadas (Magicicada spp.): Predator satiation, or too much of a good thing? This suggests a kind of tipping point: below a certain population size, the whole system starts to collapse.
Several historical broods have gone extinct, and others exist today only in small, isolated remnants. Brood XI, which was once recorded in the Connecticut River Valley, has not been seen since 1954. Urbanization, deforestation, and fragmentation of the eastern forests have eroded the habitat that sustains these populations. A strip mall built where an oak forest stood does not just displace the trees; it wipes out the nymphs living beneath them for the next cycle, and those nymphs cannot move to find new roots elsewhere.
What a Mass Emergence Does to the Local Ecosystem
When billions of cicadas die within a few weeks of emerging, their bodies blanket the ground beneath trees. That mass of organic material creates a sudden pulse of carbon and nitrogen into the soil. Research on the 2021 emergence of Brood X found that decaying cicada carcasses produced emissions of nitrous oxide and ammonia at roughly 35 times the annual average rate for U.S. forest soils, sustained over a period of about three weeks. The strongest effects occurred right at the interface where carcasses contacted the soil surface.8Applied Soil Ecology. Cicada necrobiome mediates greenhouse and trace gas pulses following periodic mass emergence
Below the surface, the nutrient surge ripples through the soil food web. Adding cicada bodies to soil around sycamore trees increased plant-available nutrient levels and changed the community of soil-dwelling nematodes, boosting populations of bacteria-feeding and fungus-feeding species. Interestingly, however, the trees themselves did not show measurable growth benefits over four years of monitoring. The nutrient pulse fed the microbial decomposer community without translating into better tree performance, at least not on a detectable scale.9PubMed Central. Acute resource pulses from periodical cicadas propagate to belowground food webs but do not affect tree performance
The emergence holes themselves also change the soil. Millions of pencil-width tunnels aerate the earth and alter water infiltration patterns in forests for months after the event. The combined effect of the tunnels, the nutrient pulse from dead adults, and the loss of nymph feeding pressure on roots makes a periodical cicada emergence one of the most dramatic ecological disturbance events in eastern North American forests.
Protecting Young Trees During an Emergence
If you live in a state that is expecting a brood emergence, the biggest concern for your yard is young, newly planted trees. As noted earlier, female cicadas target branches in a narrow size range for egg-laying, and saplings whose main stems or branch scaffolds are 5 to 10 millimeters in diameter are at the greatest risk. Established trees with thicker limbs handle the damage as a minor pruning event and typically recover without trouble.5Arboriculture & Urban Forestry. Effects and Control of Periodical Cicada Magicicada septendecim and Magicicada cassini Oviposition Injury on Urban Forest Trees
The practical advice for municipal forestry programs and homeowners is straightforward. If you are planting new trees in a year when a brood is expected, choosing genera that cicadas find less attractive can reduce the risk. Research on the Brood X emergence in the Washington, D.C., area confirmed that urban forestry departments can continue planting campaigns and avoid damage by selecting less preferred tree genera.10Arboriculture & Urban Forestry. Impacts of Periodical Cicada Egg Laying on Young Trees in the District of Columbia and Limitations of Using Remote Sensing Products to Assess Their Damage Conifers, for example, are largely ignored by periodical cicadas. If you already have a young deciduous tree planted, lightweight mesh netting with holes small enough to exclude the insects is the most effective physical barrier. Pesticides are generally considered impractical and ecologically counterproductive, given that the emergence is a short-lived event and cicadas are not pests in the traditional sense; they do not eat leaves or crops.
How Cicadas Find Each Other Above Ground
Once they emerge, adult periodical cicadas have only a few weeks to mate before they die. Males produce their characteristic buzzing songs by rapidly vibrating structures called tymbals on the sides of their abdomens. The sound is not random noise: it encodes information that females evaluate when choosing a mate. In at least one cicada species, females showed a clear preference for males producing higher-rate calls with shorter intervals between sound elements, and those males achieved greater mating success.11PubMed Central. Females prefer males producing a high-rate song with shorter timbal–stridulatory sound intervals in a cicada species
The three Magicicada species that co-emerge in any given brood each produce a distinct song, which keeps the species reproductively isolated even when they are sitting on the same tree trunk. This acoustic partitioning is critical because the species look very similar to the human eye, differing mainly in subtle abdominal coloring. The song does the species-sorting work. In dense emergences, the combined noise of millions of males can exceed 90 decibels, comparable to a lawnmower or a motorcycle at close range. Residents in heavily affected neighborhoods sometimes describe it as overwhelming, a wall of sound that persists from morning until evening for weeks.
The preference for gathering on oaks and other favored tree species means that chorusing centers, the specific trees or clusters of trees where males aggregate to sing, are not randomly distributed across the forest. They concentrate on the trees that the population has the strongest affinity for, creating hotspots of activity even within a broadly affected area. If you live in an emergence zone and want to witness the spectacle up close, finding a mature oak in a wooded setting is your best bet.