Cicada Lifecycle
All species of cicada go through three stages in their lifecycle: egg, nymph, and adult. The Egg stage begins after mating when the female lays several hundred eggs. She makes a small slit in the bark of a branch as she walks along, and pushes the eggs down through her ovipositor. She deposits 10 - 12 eggs into each slit and then moves on until all of her eggs have been laid in this manner. The eggs stay in the slits in the bark for approximately six weeks until they hatch into cicada nymphs.
During the Nymph stage, the wingless miniature cicadas fall to the ground and seek shelter underneath the leaf litter. It is thought that the tiny new hatchlings may, at first, feed on grass roots. They then begin to search for cracks and burrow down into the soil anywhere from 8 inches to 2 feet deep using their forelegs as a shovel.
Cicadas spend most of their life as nymphs underground. The cicada nymph feeds by piercing small tree roots with its needle-like mouthpart, sucking up xylem (sap). When the sap runs out, the cicada tunnels around to find a new root to feed on. While living and feeding underground they continue growing, periodically shedding their skin until they reach maturity.
The Adult stage begins when the nymph reaches full size and digs its way to the surface at night, climbs on to a tree trunk, a plant, or even a house, and sheds its skin (exoskeleton) for the last time, emerging fully grown with wings. Once emerged, the adult cicada appears white and malleable and stays this way for a few hours until it has had time to dry and fully unfurl its new wings. Periodical cicadas do feed as adults, usually using their stiff mouthparts to suck sap from twigs. This feeding does not harm or damage the twigs. Adult periodic cicadas will typically live between 2 and 6 weeks after they emerge from the ground.
Emergence
What tells a periodical cicada nymph that it is time to crawl out of the ground? Scientists aren’t really sure. One theory is that the queue comes from several signals including increased sap flow in the tree and soil temperature.
Prior to a periodical cicada emergence, the nymphs create “mud chimneys.” These are constructed when the nymph pushes mud up out of its burrow following rainy weather. If the chimney is quickly broken off, the nymph can be seen retreating down its tunnel. Annual cicada species are not known for these mud chimneys.
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