The rhythmic hum of a cicada on trees on a sweltering summer afternoon is one of nature’s most defining sounds. Often mistaken for a simple insect, these creatures are the subject of intricate biological cycles and cultural fascination. Understanding the world of the cicada on trees reveals a story of survival, transformation, and a unique relationship with the arboreal world that serves as its primary habitat.
The Lifecycle and Behavior of the Cicada
Most people encounter the cicada on trees during the height of summer, but this visible stage is merely the final chapter of a much longer life story. The majority of a cicada’s life is spent underground as a nymph, feeding on xylem sap from tree roots. This subterranean phase can last for an astonishing 13 or 17 years, depending on the species. When the soil temperature reaches a specific threshold, the nymphs emerge en masse, climb vertical surfaces, and undergo ecdysis, shedding their exoskeleton to reveal the winged adult form that fills the air with their distinctive song.
The Molting Process
One of the most visually striking events in the lifecycle of a cicada on trees is the molting process. After emerging from the soil, the nymph clings to bark or grass and splits down the back. The adult slowly pulls itself free, leaving behind the empty husk, or exuviae, which remains attached to the substrate. During this vulnerable period, the new adult’s wings are soft and crumpled, requiring several hours to expand and harden before the insect can take flight and begin its brief adult life dedicated to reproduction.
The Purpose of the Iconic Sound
The persistent, droning noise that emanates from a cicada on trees is primarily a male-driven phenomenon. Males possess specialized organs called tymbals, located on either side of their abdomens. By rapidly contracting muscles, they buckle these tymbals to produce a loud vibrating sound. This acoustic display serves a critical function: it attracts females for mating. Each species produces a unique song, allowing females to identify compatible partners even in a chorus of thousands of insects filling the canopy.
Sensory Interaction with the Environment
Cicadas are not merely loud inhabitants of the canopy; they are highly attuned to their surroundings. Their prominent eyes provide a wide field of view to detect predators, while sensitive tympanal organs located on the abdomen allow them to hear the approach of birds or other threats. Interestingly, loud machinery or human activity can sometimes disrupt their communication, forcing males to adjust the pitch or timing of their calls to overcome the noise pollution in their arboreal domain.
Impact on Trees and Ecosystems
The relationship between a cicada on trees and the host plant is generally considered to be commensal rather than destructive. While the feeding nymphs do extract sap, the volume is rarely sufficient to harm a healthy tree. The primary concern arises from the female’s egg-laying behavior. She uses a sharp ovipositor to cut slits into small branches to deposit her eggs, which can cause "flagging"—the browning and death of the terminal branch tips. However, this usually only affects young saplings, and established trees typically suffer no long-term damage.
Ecological Benefits
Despite the dramatic emergence, the cicada plays a vital role in the ecosystem. Their emergence provides a massive, protein-rich food source for a wide array of predators, including birds, squirrels, raccoons, and insects. The nutrient-rich waste (frass) they drop from the canopy acts as a natural fertilizer, returning valuable nitrogen to the soil. Furthermore, the holes created by emerging nymphs improve soil aeration and water infiltration, benefiting the root systems of the cicada on trees.
