17 Years Later
By now, you have certainly encountered a cicada or two or twenty. The raucous presence of these insects is impossible to go unnoticed. While some may find them overpowering or otherwise insufferable, the life history of cicadas is rather extreme and fascinating.
An adult Magiciada cicada (above), and a nymph prior to its final molt (below). (Photo and video by Faith Forry)
There are more than 190 species and subspecies of cicadas in North America and 3,390 varieties around the world. While cicadas generally emerge annually across the world, the United States is essentially the only place where periodical cicadas occur (aside from two species in Fiji and India). Some periodical broods emerge en masse every 13 or 17 years, with Brood X being the lucky contender for 2021. Brood X consists of three species—Magicicada septendecim, M. cassini, M. septendecula— which all have black and orange bodies and red legs and eyes. Magicicada is just one genus of cicadas (only about 0.2% of all species), but their long life span and grand emergence make them famous. Based on data from 2004, Brood X cicadas are likely to be found in the following Pennsylvanian counties: Adams, Bedford, Berks, Bucks, Chester, Columbia, Cumberland, Dauphin, Delaware, Franklin, Fulton, Huntingdon, Lancaster, Lehigh, Luzerne, Lycoming, Mercer, Montgomery, Northampton, Perry, Schuyllkill, Somerset, and York.
Cicadas are notorious for their tumultuous chorus. These love songs are “sung” by male cicadas when they flex their tymbals, which are drum-like organs in their abdomens. As tiny muscles contract the tymbal, their rather hollow abdomens amplify the sound. Tymbals are unique to male cicadas of certain species, largely for the purpose of serenading potential partners; their tymbals can be used for pre-calls to warm up, distress calls, calls to establish their territory and attract a mate, courting calls once a mate is selected, and choruses in which males synchronize their calls to attract females. Females can flirtatiously respond to their suitors by flicking their wings. This cacophonous chorus can reach decibels which are louder than lawn mowers!
Resembling termites, the nymph cicadas will eventually crawl out of their grooves, fall to the ground, and dig until they find roots to feed on. Despite common conception, the cicada nymphs are not hibernating; they actively tunnel underground and feed on tree roots until it is time for them to emerge. The mortality rate of nymph Magicicada cicadas can reach 98% in their first two years of life, which is rather astonishing! Can you imagine if these cicadas survived into adulthood? There would be unimaginable magnitudes more cicadas than the estimated millions, possibly trillions that are currently emerging. After emerging, the nymphs will climb the closest vertical surface to begin shedding their exoskeletons, at which point their wings will inflate and their adult exoskeleton will harden.
Staying underground for years at a time and emerging with millions of other individuals are thought to be strategic evolutionary adaptations; this unique life history helps them avoid predation. Once cicadas mate and lay their eggs, they promptly die. Although it is the end to their exceptionally long life, it is only a matter of time until the next brood emerges, and each successful periodical emergence spells good news regarding the state of our environment!
To read more about all things cicada, visit www.cicadamania.com.
Written by Faith Forry — June 23, 2021
