The cicadas that emerge each year create the tradition evening background sound of summer in Virginia. The males "sing" to attract a mate by popping in and out two drum-like plates (tymbals), one on each side of their abdomen, 300-400 times per second. Females as much as a mile away can be attracted by "the loudest song in the insect world."1
Periodical cicadas emerge after living underground for 13 or 17 years. Eggs laid in twigs grow into nymphs that burrow into the soil and live on tree roots. In the suburbs of Northern Virginia and elsewhere, construction projects disturb the soil and kill the underground cicadas as roads and houses are built. In the "tree save" areas and in forests not yet disturbed, the cicada nymphs can also survive for 13-17 years.
Periodical cicada nymphs emerge when the their internal calendar tells them the year is right and soil temperature at 8" of depth reaches around 68°. Stragglers can appear several years before or after their 13-year or 17-year cycle. Genetic variability results in stragglers, and that creates the potential for a brood to continue if a standard emergence year coincides with a disaster such as a hurricane or drought.2
Emerging broods are welcomed by local predators who gorge for several weeks on the sudden feast of protein, and "predator satiation" due to the massive numbers of individual cicadas ensures that enough females will mate and lay eggs to start another generation.
Broods can create dramatically high levels of noise and obvious damage to tree branches. They are sliced open when the female inserts her fertilized eggs and the tips of branches often die, deprived of water and food after the eggs are inserted. The damage to vegetation is short-term, akin to grazing by deer. The nymphs do little damage to the roots; they may even improve the soil by aerating it. The cicada can survive on the nutrient-poor sap only because they have a symbiotic relationship with specialized bacteria that produce additional proteins.3
15 broods of periodical cicadas have been identified in eastern North America. Virginia experiences eruptions of the following broods:4
Source: National Science Foundation, Cicada Data - "Family Reunion"
the genes of different species of periodical cicadas include a clock that determines when the nymphs will emerge and metamorphose into adults