People are most likely accustomed to the drone of cicadas during sweltering summer nights. These are annual cicadas, as opposed to periodical cicadas, which only appear above ground in 13- and 17-year cycles in Eastern North America. Periodical cicadas come in swarms of billions and bring a much louder buzz than what people are used to.
These periodical members of the genus Magicicada spend their years underground as maturing nymphs, feeding on nutrients from plant roots and tubers. On one hand, nymphs feed on nutrients at the roots of trees, hindering their growth, and adult females damage young trees while laying eggs. On the other hand, some weaker branches of trees may be trimmed by the cicadas, similar to pruning, and they aerate the soil around plants.They emerge all at once in late spring and molt, transforming into adult cicadas; they spend no more than a few weeks as adults to mate and reproduce before dying, returning nutrients in their remains to the soil.
This unusual life cycle most likely evolved as a response to the ice ages. Cicadas spend most of their lives below the frost line and reemerge when stimulated by soil temperature of approximately 64 degrees Fahrenheit. The cicada life cycle may also be a mechanism for avoiding predation. Since 13 and 17 are both prime numbers, it is far less likely that a species would evolve with a similar life cycle to rely on the Magicicada as a fixed food source.
Periodical cicadas are grouped into broods based on the year during which they emerge. This spring, Brood V is appearing in areas throughout the Appalachian Mountains from Lake Erie to Virginia, with the highest concentrations in Ohio and West Virginia. This brood, which has not emerged since 1999, contains three of the seven Magicicada species. It is not prominent in New York, except for in one area in Long Island (the next brood to inundate New York will be in 2018).
Periodical cicadas have often been mistakenly compared to plagues of locusts. However, unlike destructive swarms of grasshoppers, periodical cicadas and their cycles have become functioning components of ecosystems. Magicicada species rely on predator satiation: the appearance in vast numbers to reduce the overall percentage of cicadas killed. Aside from ensuring the survival of individuals that can pass on their genes, this makes periodical cicadas a food source that is able to feed a variety of opportunistic consumers.
Periodical cicadas are no strangers to changes in climate. Their unique life cycles, based on glacial periods caused by changes in the Earth’s orbit, can most likely be attributed to environmental changes. Now, Magicicada species must face Anthropocene climate change, and they will not go unaffected. Annually rising temperatures will change when soil temperatures are optimal for the cicadas’ emergence, thus leading to earlier arrivals of the swarming insects. It is possible that early appearances could even be several years out of schedule. What is even more dire is the acceleration of climate change at a pace faster than the cicadas can evolve. If the population density of a brood is too low, the effects of climate change—rising sea levels, temperature changes, species extinction, habitat destruction, and so on—could very well wipe out the genus.
Entomologists and insect enthusiasts alike track the areas and dates of emergence of periodical cicadas with aid from websites on which people can report sightings. The ascent of specific broods gives researchers fleeting opportunities to study these unique species before the next generations of Magicicada return to the earth.