By Idalia Rodriguez, Ph.D. and Charles Pumpuni, Ph.D., professors at Northern Virginia Community College
This spring, humans are not the only ones ready to leave the seclusion of their homes and start socializing!
If you live in Northern Virginia, you have probably seen the media “abuzz” with news that the cicadas are coming. After almost 17 years of living underground, Brood X (pronounced “Brood Ten”) cicadas are preparing to excavate their way to the surface to reproduce. And they will do so in very large, noisy numbers.
Naming of broods (as in Brood X) was devised to track and avoid confusion over emergence of the periodical (those with 13 and 17-year cycle), and annual cicadas (which emerge yearly). Periodical cicadas have evolved a synchronized emergence using an internal clock coupled with environmental cues to track the passage of time.
Periodical cicadas are distributed worldwide; Brood X is found only in several Midwestern and Eastern U.S. states. Here in Virginia, and especially the D.C. Metro area, we have a front seat as witnesses to one of nature’s wonders.
Brood X, species name Magicicada, will emerge in early May when the ground warms up to about 64oC and the soils are moist from heavy rains. For the past 16.5 years, Brood X have been active underground feeding on root sap (tree root xylem), molting and increasing in size.
When the time is right, the cicadas will emerge at dusk, climb up a tree (or a post), move to the upper branches, and shed their external skeletons one last time. Their exoskeletons will dot the landscape, announcing to all that the cicadas are here and let the ‘games’ begin!
According to Mike Raupp, Emeritus professor at the University of Maryland, Brood X emergence will number in the billions to trillions, and some locations may have as many as 100,000 to 1.5 million per acre.
Raupp was interviewed by the PBS News Hour during the last Brood X emergence in 2004.
The University of Connecticut has generated a map with verified locations of previous cicada emergence sites, where Brood X are anticipated to emerge again. Eastern Maryland, D.C. and Northern Virginia will likely get the best show, but cicadas may make an appearance as far south as Dale City and Manassas (Prince William County), and as far west as Purcellville (Loudoun County).
In case Brood X misses your neighborhood, the U.S. Department of Agriculture’s Forest Service has produced a map (Brood X is depicted in yellow) that shows where other large cicada broods are expected to emerge over the next decade.
Cicadas reproduce in huge numbers to increase their chances of survival. They make a great meal because they do not sting or bite and are not toxic or poisonous. The arrival of these bugs provides a tasty buffet to local predators, such as birds, snakes and the occasional pet. In small quantities, they are generally safe to eat even for you!
The 2021 Brood X singles mixer begins shortly after molting, when male cicadas ‘sing’ to attract females. Males vibrate their tymbals, a sound-making structure found on the abdomen, and with millions of male cicadas calling for mates at the same time, the noise produced can be ear- splitting. But don’t worry! You can still get a good night’s sleep, as these gentlemen cicadas only call on females during the day.
Female cicadas do not sing but respond to mating calls by flicking their wings and making clicking sounds.
After mating, female cicadas seek out trees that will provide long-term sustenance to deposit their fertilized eggs. The female cicada makes a slit in tree branches and may deposit up to 500 eggs along the branches. The branch splitting causes slight damage to the tree, but trees recover and also benefit from nutrient turnover when cicadas burrow.
Cicadas favor young saplings and ornamental trees so avoid planting trees on a year of emergence, or you may have many tiny, noisy guests visiting your backyard in 17 years!
Adult male and female cicadas live 3-4 weeks following mating. Eggs that were laid in branches hatch about 6–10 weeks later and tiny nymph (immature stages) drop to the soil and burrow underground. They dig down about 8-12 inches and begin a ‘shelter-in-place’ that will last almost 17 years.
In general, forested areas will experience greater numbers of cicadas while newer neighborhoods may see lower numbers as tree removal and soil disruption during home construction and road building kill the cicadas living underground. The more compacted soils in urban areas may also reduce the number of cicadas able to burrow back into the ground.
Tracking where cicadas are emerging is important to researchers. The University of Connecticut is tracking the 2021 emergence with a free app, Cicada Safari, and they are especially interested in hearing about stragglers. These are cicadas that do not emerge with their own brood and continue to live underground until the next brood emergence. In the long run, these “slacker” cicadas are actually beneficial for the species because diversity increases when they breed with different cicada populations.
Typical cicada burrows or “escape chimney” sightings in Northern Virginia and neighboring states are already trending on social media.
If you hear the cicada’s calling this spring, go and see what all the “buzz” is about. You may not want to miss one of the largest cicada broods emerging, because your next chance to experience them will be in 2038!
Fun Fact about Cicadas: