The Great Cicada Emergence of 2024: What to Expect
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Chapter 1: The Upcoming Cicada Phenomenon
As North America recently witnessed a solar eclipse, another remarkable natural event is approaching. From late April through June 2024, the largest group of 13-year cicadas, known as Brood XIX, will emerge alongside a 17-year brood from the Midwest, Brood XIII. This co-emergence will span 17 states, including Maryland, Iowa, Arkansas, Alabama, northern Georgia, the Carolinas, Virginia, and Maryland. Such a simultaneous emergence of two distinct broods occurs only once every 221 years, with the last occurrence being in 1803 during Thomas Jefferson's presidency.
For about four weeks, areas with trees and suburban neighborhoods will be filled with the unique sounds of cicadas' whistling, buzzing, and chirping during mating season. After mating, females will deposit hundreds of eggs in small tree branches, leading to the adult cicadas' demise. Once the eggs hatch, the new cicada nymphs will drop to the ground and burrow underground, initiating the cycle anew.
Globally, cicadas number around 3,000 to 5,000 species. However, the 13- and 17-year periodical cicadas in the eastern U.S. stand out for their extended juvenile stages underground and their synchronized mass emergences. Although two other types exist in the world—one in northeast India and another in Fiji, with life cycles of four and eight years, respectively—none match the unique traits of North America's periodical cicadas.
Periodical cicadas raise intriguing questions for entomologists and the public. What exactly do these insects do underground for 13 or 17 years? Why do they have such lengthy life cycles? What drives their synchronization? How will the two broods interact this spring? Can citizen scientists aid in tracking this emergence? Additionally, what impact does climate change have on these remarkable insects?
We study periodical cicadas to explore various questions related to biodiversity, biogeography, behavior, and ecology—essentially, the evolution and geographical distribution of life. Their scientific name, Magicicada, which derives from "magic cicada," hints at their extraordinary nature.
Understanding Their Ancient Origins
Periodical cicadas are ancient species that predate the forests they inhabit. Molecular studies reveal that approximately 4 million years ago, the common ancestor of present-day Magicicada species branched into two lineages. Around 1.5 million years later, one lineage split again, giving rise to the three modern groups: Decim, Cassini, and Decula.
Early American settlers encountered these cicadas in Massachusetts, where their sudden appearance reminded them of biblical plagues of locusts, leading to the incorrect association of the term "locust" with cicadas in North America. In the 19th century, prominent entomologists like Benjamin Walsh, C.V. Riley, and Charles Marlatt unraveled the fascinating biology of periodical cicadas, establishing that unlike locusts or grasshoppers, cicadas do not harm crops or swarm in large numbers.
Instead, cicadas spend the majority of their lives hidden underground, feeding on plant roots through five juvenile stages. Their synchronized emergences occur on a predictable 17-year schedule in the North and a 13-year cycle in the South and Mississippi Valley, creating multiple regional broods.
The Mechanism of Synchronized Emergence
A defining characteristic of Magicicada is their synchronous emergence in vast numbers, sometimes reaching 1.5 million per acre. This strategy increases their chances of mating while providing a safety-in-numbers defense against predators. Any predator that preys on cicadas—be it a fox, squirrel, bat, or bird—will fill up before consuming all available cicadas, allowing many to survive.
While periodical cicadas typically emerge on schedule, occasional groups may surface four years early or late. Those emerging early may be faster-growing individuals with ample food sources, while those emerging late may be individuals that struggled for resources. If climate conditions fluctuate, as they are currently, this adaptability becomes crucial for survival.
Will climate change disrupt the timing of Magicicada?
As glaciers retreated from present-day U.S. landscapes 10,000 to 20,000 years ago, cicadas spread through eastern forests, forming a complex network of broods. Currently, there are 12 broods of 17-year cicadas in northeastern deciduous forests, with three additional broods of 13-year cicadas in the Southeast and Mississippi Valley.
Given their sensitivity to climate, cicada populations reflect environmental changes. For instance, genetic studies suggest that the 13-year species Magicicada neotredecim, found in the upper Mississippi Valley, emerged during a previous warm period around 200,000 years ago.
As the climate warms, extended growing seasons may provide more food, potentially converting more 17-year cicadas to a 13-year cycle, similar to past shifts observed in Magicicada neotredecim.
The Role of Citizen Scientists
In 2024, 17-year Brood XIII will emerge near the 13-year Brood XIX. However, despite some media reports, these broods will not overlap; previous mapping has confirmed their distinct emergence patterns. In areas where they coexist, they appear identical in look, song, and genetics.
Researchers need precise data to track cicada distributions over time, and citizen scientists play a vital role due to the sheer size of cicada populations and the brief duration of their adult emergence. Volunteers interested in assisting with the 2024 emergence can download the Cicada Safari app to document sightings and follow ongoing research at www.cicadas.uconn.edu.
Cicadas will undoubtedly make their presence known in your area, so why not take the opportunity to appreciate them and engage in this fascinating natural phenomenon?
This article has been updated from its original version published on March 12, 2021, and is provided by The Conversation, an independent nonprofit news organization dedicated to providing context for current events.
John Cooley receives funding from the National Science Foundation and the National Geographic Society. Chris Simon has received funding from the National Science Foundation, the Fulbright Foundation, the National Geographic Society, and the New Zealand Marsden Fund.