Cicadas, known for their distinct buzzing songs, often spark curiosity due to their sudden appearances. Many wonder where these creatures go during colder seasons or when not visible above ground. This article explores the remarkable hidden life of cicadas, delving into their unique subterranean habits.
The Cicada Life Cycle
Cicadas undergo a multi-stage life cycle, beginning with eggs laid in tree branches. These hatch into tiny nymphs, which drop to the ground and burrow into the soil. This nymph stage is the extended period during which cicadas remain hidden, spending years developing underground.
The duration varies significantly between annual and periodical cicadas. Annual cicadas, despite their name, typically have life cycles ranging from two to ten years, with some emerging every summer. Periodical cicadas are known for their synchronized mass emergences, with some species spending 13 or 17 years underground before appearing.
Underground: The Hibernation Location
Cicada nymphs reside deep within the soil, creating tunnels and chambers around plant roots. They use specialized mouthparts to feed on xylem fluid, the watery sap that transports nutrients from roots through trees. This feeding provides sustenance for their long developmental period.
The depth at which nymphs live varies, typically ranging from a few inches to several feet, depending on the species and soil conditions. Periodical cicada nymphs often stay within two feet of the surface but can burrow deeper to find larger roots as they grow. This underground environment offers a stable refuge, protecting them from temperature extremes, drought, and surface predators.
Life During Hibernation
The underground period for cicada nymphs is not true hibernation like mammalian torpor, but an active phase of slow growth and development. Nymphs constantly feed on tree root sap, which is low in nutrients, requiring them to consume large quantities over many years to grow. As they mature, they undergo several molts, shedding their exoskeletons to accommodate their increasing size.
During this subterranean existence, cicada nymphs are metabolically active, steadily preparing for emergence. They build exit tunnels to the surface in their final year underground, sometimes constructing mud turrets. Nymphs typically emerge when the soil temperature at about eight inches deep reaches approximately 64°F (18°C), signaling their final transformation into winged adults.