Cicadas are a remarkable group of insects known for their loud presence and unusual life cycles. Ohio is host to two distinct populations that appear on very different schedules. The timing of their emergence is a precise biological event, dictated by years spent developing underground and specific environmental cues. The most dramatic appearances occur when entire generations rise simultaneously from the soil, creating a massive, synchronized spectacle.
Annual Versus Periodical Cicadas
Ohio hosts two main types of cicadas, which have fundamentally different emergence patterns. The most commonly heard species is the annual cicada, often nicknamed the Dog-Day cicada because it appears every summer during July and August. These cicadas belong to the genus Neotibicen and emerge in smaller, less noticeable numbers each year. While adults are seen annually, the life cycle of the annual cicada spans two to five years underground, with overlapping generations ensuring continuous yearly rotation.
The much more famous and numerous are the periodical cicadas, belonging to the genus Magicicada. These insects are known for their rigid, multi-year cycles of either 13 or 17 years, which they spend entirely as nymphs feeding on tree roots beneath the surface. When they emerge, all individuals in a given population, known as a brood, are developmentally synchronized. This results in a sudden, overwhelming mass emergence, with densities that can reach millions per acre.
Environmental Triggers for Emergence
The timing of the periodical cicada’s emergence is governed by a precise environmental mechanism after their long underground development is complete. The most important factor is the temperature of the soil, which must reach a specific threshold to signal the nymphs to surface. Nymphs wait for the soil temperature to reach 64 degrees Fahrenheit (about 18 degrees Celsius) at a depth of 8 inches before they begin their ascent.
In Ohio, this precise temperature is typically reached in late April or early to mid-May, though the exact date can shift depending on spring weather patterns. A prolonged cool spring will delay the emergence, while warm rain often acts as the final trigger by softening the soil. Once the soil hits the target temperature, mature nymphs begin tunneling to the surface, where they molt into their winged adult form.
Ohio’s Major Brood Cycles
The synchronized emergences of periodical cicadas are organized into regionally distinct groups called broods, designated by Roman numerals. Ohio is home to several broods, including the 17-year Brood X and Brood XIV. Brood X, known as the Great Eastern Brood, last emerged across parts of western and southwestern Ohio in 2021. Following its 17-year cycle, the next major appearance for Brood X is scheduled for 2038.
Brood XIV is another 17-year cycle population that covers portions of southwestern Ohio, including counties like Hamilton and Greene. This brood last emerged in 2008, meaning residents in those specific areas next witnessed its appearance in 2025. The emergence of a particular brood defines the year a region experiences the deafening chorus and high density of red-eyed insects.
The Brief Adult Phase and Event Duration
The adult phase of the periodical cicada’s life is brief, serving almost entirely for the purpose of reproduction. Once the nymphs tunnel out and molt into adults, they have only a short window of time to mate and lay eggs before they die. The entire event, from the first emergence to the death of the final adults, typically lasts only four to six weeks.
During this short period, male cicadas aggregate in trees, forming large groups called chorus centers. They produce loud, species-specific mating songs using specialized organs called tymbals. After mating, the females use an ovipositor to cut small slits into the bark of woody plants, where they deposit their eggs. The intense emergence ends by mid-summer, when the adult population dies off and the newly hatched nymphs drop to the ground to begin their 13 or 17-year journey.