Life Cycle

Eggs are laid in branches of trees and shrubs or in the stems of grasses (the nymphal food plants) in small slits cut into the surface by the female's spearlike ovipositor. The number of eggs laid in each slit varies between both species and individuals. Usually it is about 10 to 16, although the number laid per slit by a single female can range from 3 or fewer to more than 20.

A female makes many egg slits and often distributes her eggs at more than one site. A batch of eggs can number 300 or more. Some species, such as many Cicadetta, select only living tissue for oviposition, whereas others choose only dead or dying tissue. Many days, often in excess of 100, may pass before the nymphs hatch.

On hatching, the young nymphs are encased in a thin transparent skin that encloses the appendages separately but restricts their function. These pronymphs quickly wriggle their way along the egg slit to its entrance. A spine at the apex of the abdomen probably assists this exit and also in casting off the pronymphal skin. The young nymphs fall to the ground, whereupon they immediately seek shelter in the soil and later search for a root from which to feed by sucking sap.

Cicadas spend most of their life underground, slowly growing to maturity through five instars (Fig. 1). The length of life cycle is known only for a small number of species.

Some grass-feeding species mature within a year. The American periodical cicadas, Magicicada species, have a life cycle spanning 13 or 17 years, the longest known for any insect. Periodical cicadas are consistently regular in their life cycle length, but most other cicadas change by a year or two, and even individuals from a single egg batch can mature at different rates.

For most species, emergence from the final nymphal skin occurs during the first few hours after dark; the laborious process can last an hour or more. The adult life usually lasts 2 to 4 weeks, but some grass-dwelling species possibly live only 3 to 4 days. Some of the larger tree-inhabiting species probably live 8 or more weeks.

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