The distinct, loud chorus of the cicada is a familiar sound of late summer, often announcing the arrival of the season’s warmest months. This large, winged insect, sometimes mistakenly called a locust, is celebrated for its sudden, synchronous appearances. While the adult cicada lives for only a few weeks above ground, its entire existence encompasses a multi-stage process that can span many years.
The Beginning: Eggs and Hatching
The life cycle begins when the adult female uses a specialized, sharp organ called an ovipositor to deposit her eggs. She carves small slits into the bark or woody tissue of tree branches and twigs, creating a protected place for the next generation. A single female can lay hundreds of eggs, often in groups of 20 to 30 per slit.
The eggs are tiny, resembling small grains of rice tucked into the plant tissue. The developing embryos receive moisture and nutrients from the tree sap that seeps into the slit. Incubation lasts approximately six to ten weeks, depending on the species and environmental conditions.
Once the eggs hatch, the tiny, ant-sized nymphs emerge from the branch and quickly drop to the ground. Their immediate instinct is to burrow down into the earth, where they will spend the vast majority of their lives unseen.
The Long Wait: Subterranean Nymphs
The subterranean stage is the longest phase of the cicada’s life, characterized by slow growth and feeding beneath the surface. Using their strong, shovel-like front legs, the nymphs dig into the soil until they locate a root system. They attach themselves to the roots and use specialized mouthparts to draw nutrients from the tree’s xylem fluid, which transports water and minerals.
The duration of this underground period varies significantly between the two main categories of cicadas. Annual cicadas, such as the familiar “dog-day” species, spend two to five years developing as nymphs, with some individuals emerging every summer. Periodical cicadas have synchronized life cycles of either 13 or 17 years, emerging all at once in massive numbers at predictable intervals.
While underground, the nymph undergoes a series of developmental molts, known as instars, shedding its exoskeleton multiple times as it grows larger. Periodical cicadas typically go through five instar stages. Scientists hypothesize that these insects track the passage of years by monitoring seasonal changes in the chemical composition of the tree sap they consume. This ability allows them to coordinate their emergence after the precise number of years have passed.
Transformation and Emergence
The end of the nymphal stage is signaled by specific environmental cues, primarily the warming of the soil. When the soil temperature at a depth of eight inches reaches approximately 64 degrees Fahrenheit, the mature nymphs begin preparing for emergence. In the weeks prior, the nymphs construct exit tunnels, creating half-inch-diameter holes that reach the soil surface.
The mass emergence event typically occurs after sunset on a warm evening. The final-instar nymphs crawl out of the ground and immediately begin climbing the nearest vertical surface, such as a tree trunk or wall. They secure themselves firmly to this surface to undergo their final transformation.
The nymph then begins its final molt, or ecdysis, splitting its old, brown exoskeleton down the back. The soft, pale insect slowly pushes itself out of the shell, a process that can take several hours. This newly emerged insect is known as a teneral adult, characterized by a soft body and crumpled, white wings. Over the next few hours, the adult’s wings expand and its exoskeleton hardens, completing its transition into the winged, reproductive form.
Adult Life and Reproduction
The adult stage is brief, lasting only a few weeks, and is focused entirely on reproduction. The male cicada’s primary task is to attract a mate by producing its famously loud song. This sound is created by vibrating specialized drum-like membranes called tymbals, located on the sides of the abdomen.
Males often aggregate in trees to form large choruses, using their collective song to call for receptive females. Females respond to the male’s call with a quick, species-specific wing-flick or clicking sound. Once mating has occurred, the female is ready to lay her eggs, ensuring the continuation of the cycle.
Each female can lay hundreds of eggs, depositing them in tree twigs. After the eggs have been laid, both the male and female adults die, their bodies falling to the ground. The eggs will hatch six to ten weeks later, dropping the next generation of nymphs to the soil to begin their multi-year developmental journey underground.