Billions of Cicadas May Be Coming Soon to Trees Near You

rpbirdman/iStock

The key feature of Magicicada biology is that these insects emerge in huge numbers.

A big event in the insect world is approaching. Starting sometime in April or May, depending on latitude, one of the largest broods of 17-year cicadas will emerge from underground in a dozen states, from New York west to Illinois and south into northern Georgia. This group is known as Brood X, as in the Roman numeral for 10.

For about four weeks, wooded and suburban areas will ring with cicadas’ whistling and buzzing mating calls. After mating, each female will lay hundreds of eggs in pencil-sized tree branches.

Then the adult cicadas will die. Once the eggs hatch, new cicada nymphs fall from the trees and burrow back underground, starting the cycle again.

There are perhaps 3,000 to 4,000 species of cicadas around the world, but the 13- and 17-year periodical cicadas of the eastern U.S. appear to be unique in combining long juvenile development times with synchronized, mass adult emergences.

These events raise many questions for entomologists and the public alike. What do cicadas do underground for 13 or 17 years? What do they eat? Why are their life cycles so long? Why are they synchronized? And is climate change affecting this wonder of the insect world?

We study periodical cicadas to understand questions about biodiversity, biogeography, behavior and ecology – the evolution, natural history and geographic distribution of life. We’ve learned many surprising things about these insects: For example, they can travel through time by changing their life cycles in four-year increments. It’s no accident that the scientific name for periodical 13- and 17-year cicadas is Magicicada, shortened from “magic cicada.”

Natural History

As species, periodical cicadas are older than the forests that they inhabit. Molecular analysis has shown that about 4 million years ago, the ancestor of the current Magicicada species split into two lineages. Some 1.5 million years later, one of those lineages split again. The resulting three lineages are the basis of the modern periodical cicada species groups, Decim, Cassini and Decula.

Early American colonists first encountered periodical cicadas in Massachusetts. The sudden appearance of so many insects reminded them of biblical plagues of locusts, which are a type of grasshopper. That’s how the name “locust” became incorrectly associated with cicadas in North America.

During the 19th century, notable entomologists such as Benjamin Walsh, C.V. Riley and Charles Marlatt worked out the astonishing biology of periodical cicadas. They established that unlike locusts or other grasshoppers, cicadas don’t chew leaves, decimate crops or fly in swarms.

Instead, these insects spend most of their lives out of sight, growing underground and feeding on plant roots as they pass through five juvenile stages. Their synchronized emergences are predictable, occurring on a clockwork schedule of 17 years in the North and 13 years in the South and Mississippi Valley. There are multiple, regional year classes, known as broods.

Five nymphal stages of cicada development.
The five stages of the periodical cicada underground juveniles. Between each stage the juvenile cicada molts so that it can become larger. Actual size of the fifth-stage nymph is 0.83 inches. Chris Simon, CC BY-ND

Safety in Numbers

The key feature of Magicicada biology is that these insects emerge in huge numbers. This increases their chances of accomplishing their key mission aboveground: finding mates.

Dense emergences also provide what scientists call a predator-satiation defense. Any predator that feeds on cicadas, whether it’s a fox, squirrel, bat or bird, will eat its fill long before it consumes all of the insects in the area, leaving many survivors behind.

While periodical cicadas largely come out on schedule every 17 or 13 years, often a small group emerges four years early or late. Early-emerging cicadas may be faster-growing individuals who had access to abundant food, and the laggards may be individuals that subsisted with less.

If growing conditions change over time, having the ability to make this kind of life cycle switch and come out either four years early in favorable times or four years late in more difficult times becomes important. If a sudden warm or cold phase causes a large number of cicadas to make a one-time mistake and come out off-schedule by four years, the insects can emerge in sufficient numbers to satiate predators and shift to a new schedule.

Map of periodical cicada brood locations.
Broods of periodical cicadas, identified by Roman numerals, emerge on 13- or 17-year cycles across the eastern and midwestern U.S. University of Connecticut, CC BY-ND

Census Time for Brood X

As glaciers retreated from what is now the U.S. some 10,000 to 20,000 years ago, periodical cicadas filled eastern forests. Temporary life cycle switching has formed a complex mosaic of broods.

Today there are 12 broods of 17-year periodical cicadas in northeastern deciduous forests, where trees drop leaves in winter. These groups are numbered sequentially and fit together like a giant jigsaw puzzle. In the Southeast and the Mississippi Valley there are three broods of 13-year cicadas.

Because periodical cicadas are sensitive to climate, the patterns of their broods and species reflect climatic shifts. For example, genetic and other data from our work indicate that the 13-year species Magicicada neotredecim, which is found in the upper Mississippi Valley, formed shortly after the last glaciation. As the environment warmed, 17-year cicadas in the area emerged successively, generation after generation, after 13 years underground until they were permanently shifted to a 13-year cycle.

Female cicada depositing eggs on a branch.
A member of Brood X laying eggs in 2004. Chris Simon, CC BY-ND

But it’s not clear whether cicadas can continue to evolve as quickly as humans alter their environment. Although periodical cicadas prefer forest edges and thrive in suburban areas, they cannot survive deforestation or reproduce in areas without trees.

Indeed, some broods have already become extinct. In the late 19th century, one brood (XXI) disappeared from north Florida and Georgia. Another (XI) has been extinct in northeast Connecticut since around 1954, and a third (VII) in upstate New York has shrunk from eight counties to one since mapping first began in the mid-1800s.

Climate change could also have far-reaching effects. As the U.S. climate warms, longer growing seasons may provide a larger food supply. This may eventually change more 17-year cicadas into 13-year cicadas, just as past warming altered Magicicada neotredecim. Large-scale early emergences occurred in 2017 in Cincinnati and the Baltimore-Washington metro area, and in 1969, 2003 and 2020 in the Chicago metro area – potential harbingers of this kind of change.

Researchers need detailed high-quality information to track cicada distributions over time. Citizen scientists play a key role in this effort because periodical cicada populations are so large and their adult emergences only last a few weeks.

Volunteers who want to help document Brood X’s emergence this spring can download the Cicada Safari mobile phone app, provide snapshots and follow our research in real time online at www.cicadas.uconn.edu. Don’t miss out – the next opportunity won’t come until Broods XIII and XIX emerge in 2024.

John Cooley is an assistant professor of ecology and evolutionary biology at the University of Connecticut and Chris Simon is a professor of ecology and evolutionary biology at the University of Connecticut.

The ConversationThis article is republished from The Conversation under a Creative Commons license. Read the original article.

X
This website uses cookies to enhance user experience and to analyze performance and traffic on our website. We also share information about your use of our site with our social media, advertising and analytics partners. Learn More / Do Not Sell My Personal Information
Accept Cookies
X
Cookie Preferences Cookie List

Do Not Sell My Personal Information

When you visit our website, we store cookies on your browser to collect information. The information collected might relate to you, your preferences or your device, and is mostly used to make the site work as you expect it to and to provide a more personalized web experience. However, you can choose not to allow certain types of cookies, which may impact your experience of the site and the services we are able to offer. Click on the different category headings to find out more and change our default settings according to your preference. You cannot opt-out of our First Party Strictly Necessary Cookies as they are deployed in order to ensure the proper functioning of our website (such as prompting the cookie banner and remembering your settings, to log into your account, to redirect you when you log out, etc.). For more information about the First and Third Party Cookies used please follow this link.

Allow All Cookies

Manage Consent Preferences

Strictly Necessary Cookies - Always Active

We do not allow you to opt-out of our certain cookies, as they are necessary to ensure the proper functioning of our website (such as prompting our cookie banner and remembering your privacy choices) and/or to monitor site performance. These cookies are not used in a way that constitutes a “sale” of your data under the CCPA. You can set your browser to block or alert you about these cookies, but some parts of the site will not work as intended if you do so. You can usually find these settings in the Options or Preferences menu of your browser. Visit www.allaboutcookies.org to learn more.

Sale of Personal Data, Targeting & Social Media Cookies

Under the California Consumer Privacy Act, you have the right to opt-out of the sale of your personal information to third parties. These cookies collect information for analytics and to personalize your experience with targeted ads. You may exercise your right to opt out of the sale of personal information by using this toggle switch. If you opt out we will not be able to offer you personalised ads and will not hand over your personal information to any third parties. Additionally, you may contact our legal department for further clarification about your rights as a California consumer by using this Exercise My Rights link

If you have enabled privacy controls on your browser (such as a plugin), we have to take that as a valid request to opt-out. Therefore we would not be able to track your activity through the web. This may affect our ability to personalize ads according to your preferences.

Targeting cookies may be set through our site by our advertising partners. They may be used by those companies to build a profile of your interests and show you relevant adverts on other sites. They do not store directly personal information, but are based on uniquely identifying your browser and internet device. If you do not allow these cookies, you will experience less targeted advertising.

Social media cookies are set by a range of social media services that we have added to the site to enable you to share our content with your friends and networks. They are capable of tracking your browser across other sites and building up a profile of your interests. This may impact the content and messages you see on other websites you visit. If you do not allow these cookies you may not be able to use or see these sharing tools.

If you want to opt out of all of our lead reports and lists, please submit a privacy request at our Do Not Sell page.

Save Settings
Cookie Preferences Cookie List

Cookie List

A cookie is a small piece of data (text file) that a website – when visited by a user – asks your browser to store on your device in order to remember information about you, such as your language preference or login information. Those cookies are set by us and called first-party cookies. We also use third-party cookies – which are cookies from a domain different than the domain of the website you are visiting – for our advertising and marketing efforts. More specifically, we use cookies and other tracking technologies for the following purposes:

Strictly Necessary Cookies

We do not allow you to opt-out of our certain cookies, as they are necessary to ensure the proper functioning of our website (such as prompting our cookie banner and remembering your privacy choices) and/or to monitor site performance. These cookies are not used in a way that constitutes a “sale” of your data under the CCPA. You can set your browser to block or alert you about these cookies, but some parts of the site will not work as intended if you do so. You can usually find these settings in the Options or Preferences menu of your browser. Visit www.allaboutcookies.org to learn more.

Functional Cookies

We do not allow you to opt-out of our certain cookies, as they are necessary to ensure the proper functioning of our website (such as prompting our cookie banner and remembering your privacy choices) and/or to monitor site performance. These cookies are not used in a way that constitutes a “sale” of your data under the CCPA. You can set your browser to block or alert you about these cookies, but some parts of the site will not work as intended if you do so. You can usually find these settings in the Options or Preferences menu of your browser. Visit www.allaboutcookies.org to learn more.

Performance Cookies

We do not allow you to opt-out of our certain cookies, as they are necessary to ensure the proper functioning of our website (such as prompting our cookie banner and remembering your privacy choices) and/or to monitor site performance. These cookies are not used in a way that constitutes a “sale” of your data under the CCPA. You can set your browser to block or alert you about these cookies, but some parts of the site will not work as intended if you do so. You can usually find these settings in the Options or Preferences menu of your browser. Visit www.allaboutcookies.org to learn more.

Sale of Personal Data

We also use cookies to personalize your experience on our websites, including by determining the most relevant content and advertisements to show you, and to monitor site traffic and performance, so that we may improve our websites and your experience. You may opt out of our use of such cookies (and the associated “sale” of your Personal Information) by using this toggle switch. You will still see some advertising, regardless of your selection. Because we do not track you across different devices, browsers and GEMG properties, your selection will take effect only on this browser, this device and this website.

Social Media Cookies

We also use cookies to personalize your experience on our websites, including by determining the most relevant content and advertisements to show you, and to monitor site traffic and performance, so that we may improve our websites and your experience. You may opt out of our use of such cookies (and the associated “sale” of your Personal Information) by using this toggle switch. You will still see some advertising, regardless of your selection. Because we do not track you across different devices, browsers and GEMG properties, your selection will take effect only on this browser, this device and this website.

Targeting Cookies

We also use cookies to personalize your experience on our websites, including by determining the most relevant content and advertisements to show you, and to monitor site traffic and performance, so that we may improve our websites and your experience. You may opt out of our use of such cookies (and the associated “sale” of your Personal Information) by using this toggle switch. You will still see some advertising, regardless of your selection. Because we do not track you across different devices, browsers and GEMG properties, your selection will take effect only on this browser, this device and this website.