The sudden, loud emergence of cicadas transforms quiet summer landscapes into buzzing, high-energy ecosystems. These insects, known for their powerful, deafening songs, spend only three to six weeks above ground as adults after years of silent development. This intense, short-lived period of activity naturally leads to the question of rest: do these highly motivated, noisy creatures ever sleep? The answer requires looking beyond the familiar definition of sleep, which is tailored to mammals. Cicadas do not experience rest like humans, but they certainly undergo periods of profound inactivity essential for their survival and brief adult life cycle.
Understanding Insect Rest and Quiescence
Insects, including cicadas, do not experience sleep in the same way that vertebrates do, lacking the distinct brain wave patterns like Rapid Eye Movement (REM) sleep. Instead, they enter a state known as behavioral quiescence, which serves a similar restorative function. Quiescence is defined by a prolonged period of reduced movement and a significantly lowered responsiveness to external stimuli. If a light touch or mild sound would normally cause an insect to move, during quiescence, a much stronger stimulus is required to rouse it, indicating an increased sensory threshold. This period of stillness is a biological requirement, similar to human sleep, necessary for repairing cellular damage and conserving energy. Studies on other insects show that if they are deprived of this quiescent state, they will later exhibit a “sleep rebound,” meaning they compensate by resting for a longer duration.
Daily Activity Cycles of Adult Cicadas
The adult cicada’s life is governed by a strongly diurnal cycle, meaning their activity is concentrated during the daylight hours. Male cicadas spend the majority of the day engaged in their most recognizable behavior: singing to attract mates and establish chorus centers. This period of high activity also includes feeding on tree xylem fluid and, most importantly, mating, which is the sole purpose of their brief time above ground.
As the sun sets and air temperatures drop, the cicadas’ intense activity comes to a near-complete stop. They enter a state of behavioral quiescence, often clinging motionless to the bark or leaves of trees and branches where they spent the day. The insects remain still and unresponsive throughout the night. This nightly period of quiescence is the adult cicada’s regular, restorative rest, ensuring they have the energy reserves needed for the demanding and noisy activities of the next day.
The Long Dormancy of Cicada Nymphs
The most substantial period of a cicada’s existence is spent in a form of extended dormancy as a nymph, living underground for a species-dependent duration of two to 17 years. During this time, the nymph feeds on the xylem fluid from tree roots, slowly growing through five developmental stages called instars. The nymphs are metabolically active throughout these years, but their lifestyle is one of profound behavioral quiescence compared to their adult counterparts.
This subterranean phase represents nearly 99.5% of the insect’s entire lifespan, characterized by low energy expenditure and minimal movement. Though they are actively tunneling and feeding, their overall existence is a slow, quiet development in the dark soil. This long-term, quiescent state is a necessary form of prolonged rest, enabling the insect to accumulate the energy required for its massive, synchronized emergence and the intense, final weeks of its adult life.