A cicada synchronized with its brood stands a chance.
The insects’ coordinated emergence is deemed an evolutionary tactic by scientists. Predators such as birds and raccoons can only consume so many of them. Therefore, the more cicadas emerge simultaneously, the greater the likelihood that more will survive to reproduce and pass on their genetic traits.
“They employ the safety-in-numbers approach,” remarked Chris Simon, an ecology and evolutionary biology professor at the University of Connecticut specializing in the insects.
Contrarily, the rare cicadas that miscalculate their timing and emerge alone are often labeled as “stragglers.” Most small clusters of stragglers fall prey and fail to perpetuate their lineage.
“Natural selection favors individuals who wait, as those who don’t are swiftly consumed,” Simon explained.
This summer, an unusually large number of periodical cicadas are anticipated to emerge as two broods coincide. The last such occurrence was in 1803.
Tens of billions of these insects are projected to appear. Users of the
Cicada Safari app, which aids in reporting cicada sightings and tracking them for scientific purposes, have logged over 1,000 sightings in Georgia and hundreds in North Carolina and Alabama.
Periodical cicadas are categorized into two types of broods, each with distinct emergence cycles of either 13 or 17 years. Temperature appears to trigger their emergence, yet the precise mechanisms governing their synchronized emergence remain somewhat enigmatic.
Moreover, scientists have observed alterations in the insects’ patterns, leading to hypotheses that rising temperatures may be altering the internal clocks of certain periodical cicadas.
Gene Kritsky, an entomologist and cicada expert at Mount St. Joseph University in Ohio, noted that as average temperatures have increased due to global warming, emergence dates have shifted earlier in the year.
“Cicadas are creatures of climate,” he asserted, adding, “They’re emerging nearly 10 days to two weeks earlier than in 1940.”
John Cooley, a cicada researcher at the University of Connecticut who maps cicada broods, anticipates the insects’ range to shift northward as the climate warms and the plant species they rely on migrate north.
He also highlighted a rise in reports of stragglers, a phenomenon intriguing researchers.
“If you examine the data, we undeniably have more reports of straggling now than in the past,” Cooley observed. “This could be due to increased straggling or simply because of widespread internet access, enabling individuals to report sightings.”
Simon mentioned that Brood XIII, emerging this year, produced a record number of stragglers in 2020.
“Four years ago, there were so many that they remained active for the entire four weeks,” she recalled. “They weren’t entirely consumed. They were able to mate and lay eggs, potentially establishing a new population.”
“They’re certainly responding to climate warming and changes in the growing season,” Simon added.
Simon theorizes that climate change may be lengthening the growing seasons of the plants cicadas feed on, accelerating the insects’ development underground. Consequently, more “stragglers” may emerge prematurely. Eventually, she predicts the entire population will adapt and adjust their timing.
Simon forecasts that 17-year cicada broods will transition to 13-year cycles, and 13-year cicadas may emerge every nine years.
If proven accurate, this theory would underscore how climate change disrupts the natural rhythms governing the world.
Periodical cicadas, harmless to humans, are distributed throughout the Eastern and Midwestern U.S. Unlike annual cicada species, which appear yearly, the emergence of periodical cicadas like those presently emerging in the Southeast is an extraordinary event. The U.S. hosts 12 broods on 17-year cycles and three on 13-year cycles.
During their subterranean years, periodical cicadas feed on plant roots. Upon surfacing, they engage in a cacophonous mating ritual, striving to reproduce before becoming prey for birds or raccoons.
“This aspect has never been studied,” Simon remarked.
