As temperatures rise and summer approaches, the United States prepares for a remarkable natural event: the emergence of two distinct broods of periodical cicadas, Brood XIX and Brood XIII, but the former may be extinct in Louisiana, according to a researcher and professor at LSU. 

Chris Carlton, a professor emeritus and researcher with the LSU Entomology Department, said poor documentation of Brood XIX’s last resurgence in northern Louisiana has led entomologists, including himself, to believe that the cicadas may have gone extinct in the state. 

“In 2011, there was a scheduled emergence of Brood XIX, and there were no reliable records from Louisiana,” Carlton said.

Periodical cicada broods can face challenges that lead to extinction or local disappearance, according to Carlton. 

“Habitat destruction and modification, such as clearing forests, can disrupt the emergence area and prevent cicadas from completing their life cycle,” he said.  

“If you have a brood that emerges in a one-acre forest, and you go in and clear the forest anytime during 13 years, you kill the cicadas, and the forest may grow back.” Carlton explained. “But it destroys it during a brief period of time enough so that it kills that little emergence area. And they never recover.”

Pesticides can also impact cicada populations. The insects spend the majority of their lives underground, feeding on the xylem of plant roots. 

Brood XIX and Brood XIII belong to a special group known as periodical cicadas that lie dormant longer than others. Periodical cicadas typically live underground for a period of either 13 or 17 years before emerging. 

The 13 and 17-year cycles of these cicadas are particularly significant because they are prime numbers. Prime numbers are only divisible by themselves and one, making their cycles unique.

 ”The fact that their cycles are prime numbers means that they don’t overlap often. This ensures that each brood can emerge in synchrony and maintain its distinct cycle,” said Carlton. 

This year, 13-year Brood XIX and 17-year Brood XIII will emerge simultaneously for the first time in 221 years. 

The emergence of Brood XIX and Brood XIII will span several states, including Alabama, Arkansas, Georgia, Illinois, Indiana, Iowa, Kentucky, Louisiana, Michigan, Mississippi, Missouri, North Carolina, Oklahoma, South Carolina, Tennessee, Wisconsin and Virginia. 

Most states are home to either Brood XIX or Brood XIII. Only a narrow strip of Illinois will observe both broods in the same place. 

The cicadas’ emergence is not only a spectacle, but also a crucial event in the ecosystem. These insects are a vital food source for birds, mammals and even snakes.

 ”Copperheads will climb trees in search of newly emerged cicadas. It’s the only time of year you’ll see copperheads climbing trees,” Carlton said. 

While adult cicadas arrive en masse, they pose little risk to plants on farms or in gardens, according to the EPA. They don’t eat leaves, flowers, fruits or produce; above ground, they only consume small amounts of sap from trees and shrubs. 

Cicadas belong to the family Cicadidae, which includes over 3,000 species globally. In Louisiana, there are several species of cicadas, including annual Dog Day cicadas and periodic cicadas like Brood XIX.

Dog Day cicadas get their name from coming out during the dog days of summer.  They remain in the ground for three years, but unlike periodical cicadas, there’s no synchrony in their emergence, according to Carlton. 

Male cicadas use their songs to attract females for mating. Different species of cicada produce distinct songs when they emerge from underground.

“The males sit in the tree, and they sing their songs; the females of the same species hear the song,” said Carlton. 

This ensures that cicadas breed with the same species, maintaining the genetic integrity of each population.

“The sound is almost piercing. It’s worse than crickets,” said Payton Autry, an LSU freshman, describing the sound of the cicadas. Louisiana residents are familiar with the annual emergence of Dog Day cicadas, which appear in late May to early June. 

“If citizen scientists will keep their eyes and ears alert for possible occurrences, we can perhaps resolve the question of whether Brood XIX is still in the state,” Carlton said.

He encouraged people to upload pictures of the cicadas to platforms like iNaturalist.org, a popular site for documenting and sharing observations of biodiversity.

“If we have enough people looking, we can actually figure out whether they’re gone,” he said. 

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