Along with donning face masks, some North Carolinians may also be wearing earplugs! After nearly two decades underground, a wave of periodical cicadas is beginning to emerge this month and they will be a noisy bunch! Last spotted in 2003, a group of 17-year cicadas referred to as Brood IX will rise from the soil in Virginia, West Virginia, and northwestern North Carolina starting in mid-May. In North Carolina, these insects are expected in Ashe, Alleghany, Forsyth, Stokes, Surry, and Wilkes Counties.
Cicadas are large insects in the order Hemiptera. With 190 species and subspecies existing on every continent except Antarctica, many are familiar with their loud mating songs. Of particular interest are periodical cicadas (genus Magicicada), which emerge concurrently after either 13 or 17 years and are organized by geography and year of emergence into “broods”. While cicadas are often incorrectly called ‘locusts’ due to their mass emergence, locusts are actually an entirely different groups of insects.
The lifecycle of cicadas begins with egg-laying. Adult females lay eggs in tree limbs after cutting a slit in the bark. This creates grooves in the limbs which make tree fluids available for their young to feed on. Unfortunately, these grooves can sever twigs and cause the leaves to turn brown, a condition called flagging. Cicadas may be particularly concerning to owners of nurseries and orchards because they can cause severe flagging on young trees. To combat this, owners can place screening material over trees to block access. In most cases however, cicada damage does not cause long-term impacts to tree health.
After eggs hatch, the young cicadas temporarily feed on tree fluids before falling and burrowing into the ground. The young, called nymphs, feed on roots underground, something that periodical cicadas do for 13 or 17 years. After emerging, they climb trees and shed their exoskeletons, becoming adults to mate and start the cycle over again.
The reason that periodical cicadas emerge in 13- or 17-year cycles is still not completely understood Research suggests that it could be a strategy to avoid predators. By maintaining long lifecycles, cicadas make it difficult for predators to evolve to specifically feed on them. Further, the large numbers of cicadas that emerge ensure that predators are overwhelmed so that enough cicadas can live to continue their brood.
While individuals of Brood IX are scheduled to begin their adult lives above-ground this year, they are accompanied by stragglers from other broods, most notably Brood XIX. Brood XIX is a group of 13-year cicadas that was last seen in 2011 and was expected to emerge in 2024. However, some members of this brood did not mark their calendars and have been sighted up the East Coast, including in North Carolina, emerging 4 years early! While this is odd, it is not unheard of. Periodical cicadas tend to emerge 1 and 4 years early, and 13-year cicadas emerging 4 years early is well-documented. For instance, in 2017, Brood X came 4 years early in Washington, D.C., Virginia, and Maryland. Stragglers from Brood X and Brood XIII are also expected to appear this year. Expected brood emergence is well-documented and tracked each year.
What clues should you look for to spot these cicadas for yourself? Other than the cicada itself or its shed exoskeleton, cicadas create structures in soil called chimneys or “turrets” above the holes from which they will emerge. You might also see holes about the size of an adult finger near trees, and you can even spot some young cicadas under stones. If you happen to see cicadas, you can help researchers by recording your sighting on an app called Cicada Safari. By submitting pictures or videos to the app, users can map the location of cicadas, helping researchers understand more about this fascinating insect. If you snap a photo of the underside of a cicada, you can even assist scientists in determining which brood the individual is from!
So, keep an eye (or ear) out for cicadas! Maybe you can listen to the loud song of these insects in wonder over the next few weeks as you realize that they have waited 13 or 17 years for this moment. And, even if you aren’t too fond of cicadas, you can still contribute to science by adding your sightings to the Cicada Safari app!
Blog written by Courtney Smith, N.C. Forest Service Forest Health Intern