If you haven’t heard about the 17-year emergence of periodical Brood X cicadas, perhaps you’ve been the one living underground. Cicadas are emerging from their long sleep in 15 midwestern and northeastern states, but not everyone will see or hear them. Entomologist Art Evans, a longtime adjunct professor in the biology department, explains the noisy insects and where they may pop up.

What is a cicada? And what type are many people seeing this spring and summer?

Cicadas are robust insects with four clear wings and piercing-sucking mouthparts. Most of their lives are spent underground as flightless nymphs with powerful forelegs adapted for digging. They burrow along the root systems of trees and suck sap from roots. After two or more years, the fully grown nymphs emerge from their burrows at night and climb up trees, fences, and other vertical surfaces to complete their development. Soon their exoskeleton splits open along their backs and the soft and pale adult emerges. The freshly emerged adult leaves its shell and spends the next several hours pumping fluids out of its abdomen to expand its wings while its exoskeleton darkens and hardens. By morning, it is ready to take to the air in search of a mate. Males produce their distinctive calls with special organs that are amplified by air sacs in their abdomen. These calls attract the mostly silent females. After mating, the female uses her specialized egg-laying structure to cut slits in plant stems to deposit an egg in each slit. The hatching nymphs drop to the ground and begin their subterranean lives. Of the 3,400 species of cicadas known worldwide, most live in the tropics.

More than 170 species occur in North America, north of Mexico, of which at least four occur on the grounds of the University of Richmond. In the U.S., there are two kinds of cicadas — periodical and annual. Periodical cicadas are typically black with orange markings, have red eyes, and emerge in the spring every 13 or 17 years. Annual cicadas are generally green with black or brown markings with greenish eyes and appear every summer. The 2021 emergence is of 17-year cicadas is known as Brood X, pronounced as Brood 10.

Where are Brood X cicadas appearing?

Periodical cicadas all belong to the genus Magicicada and are found only in the eastern United States. Their emergences of 13 or 17 years are grouped into geographic broods, each identified with a Roman numeral. Brood X — the largest of the 17-year broods — is sometimes called the Great Eastern Brood and was first described in 1715. The 2021 emergence is taking place in three areas across 15 states, including northern and extreme western Virginia. Brood X includes three species that are distinguished from one another both by size and the male’s call. They began emerging in small numbers in late April, but cool weather delayed their peak emergence until late May and by early July they will be mostly gone.

For those living in areas with Brood X cicadas, what might they notice in their backyard?

People will likely see emergence holes and piles of shells beneath trees and shrubs, along with numerous adults resting on vegetation. After several days of warm weather, the males will begin to call. The chorus of one species, M. septendecim, has been likened to someone calling “pharaoh.”

What can we learn from studying cicadas?

Cicadas are an important component of forest nutrient cycles. The nymphs are long-lived and relatively sedentary animals. Understanding their evolutionary adaptations for dealing with adverse environmental conditions offers insights into how subterranean organisms deal with various environmental stressors. The surfaces of cicada wings have super-hydrophobic, self-cleaning, anti-reflective, and antibacterial qualities. Bioengineers are developing materials that mimic these surfaces that achieve these desirable qualities. Finally, pharmacological studies of a fungus that is sexually transmitted among cicadas may lead to the discovery of new therapeutic drugs.