Cicadas are fascinating insects known for their distinctive sounds and synchronized appearances. These creatures spend most of their lives hidden beneath the ground, emerging only for a brief adult stage to mate and lay eggs. Their unique life cycles and the environmental conditions of different regions determine where and when these remarkable insects appear across the United States. Their patterns reveal a complex interplay between biology and geography.
Understanding Cicada Types and Their Habitats
Cicadas are broadly categorized into two main groups: annual cicadas and periodical cicadas. Annual cicadas, often called “dog-day cicadas,” appear every summer. Their emergence is not synchronized, meaning some individuals from a population mature and emerge each year. These cicadas are common in various forested and wooded areas.
Periodical cicadas, on the other hand, are known for their synchronized mass emergences after either 13 or 17 years spent underground. During their subterranean phase, nymphs feed on xylem fluids from tree roots. Adult periodical cicadas live only for about four to six weeks, focusing on mating and reproduction before they die.
States Hosting Major Periodic Cicada Broods
The year 2024 saw a particularly notable event with the co-emergence of two major periodical cicada groups: Brood XIII (a 17-year cicada) and Brood XIX (a 13-year cicada). Brood XIX, sometimes called the Great Southern Brood, emerged across a wide range of states. These included Alabama, Arkansas, Georgia, Illinois, Indiana, Kentucky, Louisiana, Mississippi, Missouri, North Carolina, Oklahoma, South Carolina, Tennessee, and Virginia, with some presence also noted in Iowa.
Brood XIII, known as the Northern Illinois Brood, emerged primarily in Illinois, Iowa, and Wisconsin, extending into parts of Indiana and Michigan. Illinois was the only state where there was potential for the geographical ranges of both Brood XIII and Brood XIX to overlap and intermingle. Looking ahead, Brood XIV, a 17-year cicada, is anticipated to emerge in 2025 in states such as Kentucky and Tennessee, along with portions of Georgia, Illinois, Indiana, North Carolina, Virginia, West Virginia, Massachusetts, central Pennsylvania, and Long Island, New York.
Widespread Presence of Annual Cicadas
Unlike the specific, large-scale emergences of periodical cicada broods, annual cicadas are widely distributed across the United States. These include species like the “dog-day cicadas” (Neotibicen species), which can be found in nearly every continental state. Some states, such as California, host a remarkable diversity of annual cicadas.
Instead, some individuals from these populations appear every summer, leading to their “annual” designation. They are commonly found in areas rich with trees, including natural forests, woodlands, parks, and even urban environments where suitable habitats exist. Their presence provides a consistent, albeit less dramatic, summer soundtrack across much of the country.
Environmental Factors Shaping Cicada Geography
The geographical distribution of cicadas is significantly shaped by specific environmental factors. Soil temperature is a primary trigger for cicada emergence, with nymphs typically surfacing when the soil at a depth of 7 to 8 inches reaches approximately 64°F (18°C). This temperature dependency explains why cicadas often emerge earlier in southern and lower-elevation regions, where the soil warms more quickly.
Soil composition is another important factor, as cicada nymphs spend years burrowed underground, feeding on plant roots. The presence of deciduous trees is particularly important for periodical cicadas, as females lay their eggs in tree branches, and nymphs depend on tree roots for sustenance throughout their long developmental periods. Consequently, areas with abundant, healthy trees provide the necessary habitat for cicada populations to thrive.