Top Ten things to know about Brood X periodical cicadas

Authors: Angie Macias, doctoral student in plant and soil sciences; Brian Lovett, entomologist and post-doctoral fellow; and Matt Kasson, associate professor of forest pathology and mycology, West Virginia University Davis College of Agriculture, Natural Resources and Design.

When and where can we expect Brood X periodical cicadas this year?

Brood X periodical cicadas are set to emerge in at least 15 states in late May. Across West Virginia we can expect them in Berkeley, Grant, Hampshire, Hardy, Jefferson, Mineral and Morgan counties in eastern West Virginia. Adult cicadas (three different species) will remain active through the end of June.

Is this the eighth plague?

Cicadas are not locusts, and this is not a plague. It’s an awe-inspiring culmination of 17 years of quietly feeding on sap from roots underground. Although cicadas seem to appear out of nowhere, they have spent the last 17 years feeding underground to emerge and complete their development into adults that mate and die.

How do periodical cicadas coordinate emergence at the exact same time despite being in the dark underground for 17 years?

Cicadas have their mouths planted firmly into the roots of plants. Imagine spending a year drinking an endless smoothie. You may get bored of the flavor after a few months, and you would certainly notice if it changes. Cicadas count sap cycles in trees that are tied to seasonal changes, like leaf gain and leaf loss. This “sappy sense” can be further supported by seasonal temperature changes in the soil. These factors can orchestrate a synchronized emergence of billions of cicadas, but there are still some that come up earlier or later than all the rest. In fact, some even come up years earlier or later (four years to be exact). These cicadas are not likely poor counters; rather, the temperature and sap cues they are taking from the tree they’re drinking changed the course of their development and emergence. These out-of-season individuals are hard to notice because they may join in the wrong brood or be quickly eaten by predators.

Should I be scared or concerned?

Despite having two red eyes, they are innocently trying to find a mate to ensure the next generation of cicadas can have their own grand appearance in 2038. Will they fly towards you and land on you? Yes. In fact, since their survival strategy is to clumsily overwhelm predators with numbers, cicadas are particularly harmless. Still, it’s natural to feel concerned when billions of large, loud insects show up all at once. The reality is that cicadas have no interest in you.

Could they hurt me?

Cicadas have mouthparts adapted for sucking plant sap, like lips pursed into permanent straws. This mouth is simply not made to harm anything other than plants. And those large sword-like structures on the back of females are not stingers. That’s a specialized structure called an ‘ovipositor’ that’s used for laying eggs inside tree branches. Now if you are a small tree reading this you may want to prepare yourself. The act of hundreds of females laying eggs into the branch tips of young plants could cause them to die back. More mature plants benefit from the “pruning” service provided by the females, and will branch and grow more robustly in the years after a cicada emergence.

If cicadas don’t pose risks to us, why are people so worried about their emergence?      

Besides the sheer abundance of cicadas (billions of inch long insects), their only annoyance may be the deafening noise of male cicadas serenading females. It can be so deafening because three species of cicadas make up Brood X. Male cicadas have specialized organs called ‘tymbals’ to generate sound, and also have hollow abdomens that act like amplifiers to make their particular sound even louder. Since each species has its own special mating call, mixing all three at once makes a cacophonous shrill. Females do not sing, but they can applaud the males by snapping their wings when they’ve found an impressive mate. These snaps signal to the males that they are open to mating.

Do periodical cicadas benefit any other organisms?

Periodical cicadas have a pretty wild defense strategy: fill the bellies of your predators until they are so bloated and lethargic that the remaining cicadas can succeed. Cicadas also provide a huge influx of natural fertilizer for plants and microbes following their death, piling up in masses at the bases of trees and in parking lots. Carpets of decaying cicadas redistribute nutrients slowly slurped from the roots of local plants over 17 years. If you watch bird, fish, reptile, and amphibian populations in the year periodical cicadas emerge, you will see a dramatic spike in the populations of all these animals because of the cicada cornucopia. Many chefs are dusting off recipes for these nutty-tasting insects.

I live in West Virginia and the periodical cicadas emerged in 2016. Why are they called 17-year cicadas if they emerge every few years?

The cicadas that emerged in the Morgantown area in 2016 (Brood V), the Northern Panhandle in 2019 (Brood XIII) and in southern West Virginia in 2020 (Brood IX) are also 17-year cicadas. West Virginia is located such that several different 17-year populations or broods overlap. So each population takes 17 years to complete their life cycle, but their years of origin (or broods) differs. There are also 13-year cicadas, but no 13-year cicadas occur in West Virginia.

What is a “zombie cicada?”

“Zombie cicadas” refers to cicadas that are infected by a fungus called Massospora. The fungus makes the cicada butts and genitalia fall off: replacing the back side of their body with a mass of fungal spores. The fungus spreads while the cicada attempts to mate or fly through the air. The fungus doesn’t kill them outright, but instead turns them into amorous fungus spreaders.

How can I make the most of this emergence?

This emergence is an opportunity to help build our understanding of cicadas by recording what you see. Start by downloading the iNaturalist and Cicada Safari apps to help you see where cicadas are emerging and add your observations to help scientists know where cicadas are showing up. To get an idea where cicada densities will be highest, check out the 2004 emergence data here: Brood X | Cicadas (uconn.edu). For up-to-date maps during emergence use the iNaturalist and Cicada Safari apps. For more information on periodical cicadas, check out Periodical cicada Brood X (10).