When people search for “baby cicadas,” they are looking for the insect’s juvenile form, which biologists call the nymph. Unlike many other insects, cicadas do not undergo complete metamorphosis with a larval stage, but rather a gradual transformation. The nymph is fundamentally different from the adult in both appearance and lifestyle, spending the vast majority of its existence hidden from view. This subterranean stage is a prolonged period of growth and development before the emergence of the winged adults.
Defining the Cicada Nymph Stage
The cicada’s life cycle follows a pattern of incomplete metamorphosis, consisting only of the egg, nymph, and adult stages. The nymph generally resembles a wingless, miniature version of the adult, adapted for its environment. Upon hatching from an egg laid in a tree branch, the tiny nymph drops to the ground and immediately burrows into the soil. The nymph stage is defined by its long-term residence underground, where it feeds on the xylem fluid of plant roots. This sap-feeding sustains its growth through multiple molts (instars) over many years. The duration of this life stage varies dramatically by species, ranging from a few years for annual cicadas to 13 or 17 years for periodical cicadas.
Physical Description of the Subterranean Nymph
Because the nymph is shielded from sunlight and lives surrounded by soil, its exoskeleton is typically soft and pale. Its coloration is creamy white, light tan, or yellowish-white, often stained by the surrounding earth. The most distinctive feature of the subterranean nymph is its heavily modified pair of forelegs, adapted for digging. These specialized, shovel-like limbs are known as fossorial legs, and they are larger and more muscular than the other legs. They are used to tunnel through the soil and excavate chambers near tree roots. The nymph’s body is compact and robust, lacking the large, clear wings that characterize the adult stage. The developing wings are only visible as small, inconspicuous pads on the thorax. The size of the earliest instars gradually increases over years until the nymph is nearly the size of a mature adult cicada.
Identifying the Emerging Nymph
The final instar nymph undergoes a physical transformation just before it is ready to emerge from the ground. The nymph’s pale exoskeleton begins to darken significantly, shifting to a dark reddish-brown or nearly black color. This darkening is often concentrated on the thorax, where prominent, dark wing pads become clearly visible, housing the fully formed adult wings inside. The mature nymph then constructs an exit tunnel and crawls out of the soil, usually after the ground temperature at a depth of about eight inches reaches approximately 64 degrees Fahrenheit. Upon emergence, the nymph climbs a vertical surface, such as a tree trunk or a fence post, for its final molt. The empty, rigid, brown shell left clinging to the surface is called the exuvia. This abandoned casing is often the most common sight people encounter, retaining the exact shape of the nymph, including the distinctive fossorial forelegs and the prominent wing pads.