Cicadas are coming, bringing mysteries that fungus scientists hope to study

The last time these swarms were present at the same time was in 1803, when Thomas Jefferson was president and the Louisiana Purchase had just been completed—meaning that many of the states with cicada love songs filling the air hadn’t even officially become part of America.

Impressively, this year’s entomological phenomenon will be particularly special for researchers hoping to unravel the mysteries of the evolution of insects that only crawl out of the ground somewhere between 13 and 17 years ago.

Cicada nests are different from species, and each nest can contain multiple cicada species, which can appear in different places. In 2024, all seven cicada species will be present, a coincidence that won’t happen again until 2037.

That means this year’s emergence will be a data collection gold mine.

One of the more unusual mysteries that scientists hope to investigate involves a parasitic fungus that attacks adult cicadas, turning them into what experts call “flying salt shakers of death.”

“So from the perspective of a scientist interested in cicadas, it’s pretty spectacular,” said mycologist Matt Carson of West Virginia University.

Cicadas are true insects in the order Hemiptera. Adult cicadas are large, loud, and very noticeable, and are known for their repeated mating calls. But cicadas spend most of their lives underground as nymphs.

Cicada nymphs are probably one of the most underappreciated forest herbivores because they spend most of their time out of sight, surviving by sucking sap from the roots of trees and other plants. They appear in the spring or summer, when the soil temperature about a foot underground reaches 64 degrees. The nymph then climbs onto the nearest vertical object and metamorphoses into an adult. These winged adults spend a short, noisy life mating and, in the case of females, laying eggs.

Cicadas can be divided into two types: annual cicadas, which usually have black or green eyes and are heard every year, and periodic cicadas, which usually have red eyes and appear only every 13 or 17 years.

Although they are nymphs, these long-lived insects must burrow below the frost line to escape the cold. In some parts of its range, such as Wisconsin, this can mean living at depths more than five feet below the surface.

This makes every occurrence important to scientists. Researchers studying zebras or puffins may have to endure harsh conditions or dangerous journeys if they want to collect genetic samples, but at least these animals are almost guaranteed to turn up in any given year. This is not true for certain cicada species. Technically, they may be there, but they are too deep underground to be easily found or accessed without causing significant harm to the animals. (Carson said he had tried and found nothing.)

Additionally, cicada hatches often don’t synchronize; it’s been nine years since this last happened. When they overlap in time, they tend to be dispersed in space, occurring several states away from each other.

This means that some questions can only be surveyed at certain times and in certain places, depending on what nests are on deck that year and what species they contain.

This year, though, cicadas from Nest XIX and Nest XIII will face off against each other, mostly in Illinois. This is where things get scientifically exciting.

Carson hope to learn A parasite called Massospora. When this fascinating fungus infects adult cicadas, it injects large amounts of amphetamines and psilocybin into the insects, both of which appear to affect their behavior.

For example, although the fungus has taken over the lower third of its body, replacing its abdomen and genitals with fungal tissue, the cicada appears to feel no pain. Instead, infected cicadas seem to want to party.

“There was some hypersexuality,” Carson said. “The males will pretend to be females to attract other healthy males to try and mate with them. This may be the fungus’s strategy to increase the number of individuals it can infect.

This parasite typically affects less than 5% of a given cicada population. But once infected, those chalky white bellies spread the spores everywhere.

Carson is trying to do genetic work to learn more about how the fungus persists in an animal with such an unusual and disjointed life cycle. This year, for the first time, he will collect contemporary samples from 13-year-old descendants—old, archived samples have been used in the past—which could yield some interesting results.

“Although our data are limited, some of the DNA sequence data from the 13-year litter is different from some from the 17-year litter, which makes me wonder if there really are some genetic differences in these strains,” he said.

Carson added that researchers are also interested in the fungus as a source of new drugs. It has been used as a traditional medicine to treat inflammation in Chinese and New Zealand Maori cultures.

Since Nest XIX and Nest XIII overlap in very few areas, it is unlikely that the number of cicadas in any one location is twice as high as usual. (With millions of cicadas per square acre present, double that would be too much.) Most people are also unlikely to notice a difference between cicada populations in two adjacent areas.

“They look exactly the same. They sound the same. Genetically, they’re almost identical,” said Chris Simon, an evolutionary biologist at the University of Connecticut.

This is not always the case. For example, new tredchim is a 13-year-old cicada that will emerge this year as part of Illinois’ XIX nest.The species is nearly twice the size of magical seventiesit will also appear as part of Nest Thirteen, appearing a little further north in Illinois, as well as in Iowa and Wisconsin.

For scientists like Simon, the real opportunity lies in less obvious differences. She wants to learn more about how cicada nests count years, which she is trying to understand by sequencing the entire genome and looking for genes or genomes that control whether cicadas follow a 13- or 17-year cycle.

“One of the most interesting things is that we think of grades or groups as being reproductively isolated because we think they have exact life cycles and the adults never meet,” Simon said. “But it turns out that’s not accurate, sometimes they’re four years early, or four years late.”

This means that different groups can still exchange genes with each other, which may drive further evolution of the species.

“When 13-year-old and 17-year-old cicadas emerge in the same year, you can actually conduct hybrid experiments,” Simon said. The last time she had the opportunity to do such work was in 2015, and before that in 1998.

Simon added that imprecise timing of cicada growth is thought to be increasing due to climate change, which lengthens the nymphs’ growing season underground. Likewise, climate change will affect their distribution, as evidenced by the increasing number of Brood VI species in the Washington area in recent years, she said.

Sometimes, over hundreds of thousands of years, a seventeen-year-old cicada will become a thirteen-year-old cicada.

Other scientists hope to learn more about how cicadas affect the plants they feed on and how trees defend themselves against herbivores. For example, some studies show reduced growth of tree rings and reduced yields in orchards infested with cicadas.

However, cicada presence also has ecological benefits, providing a smorgasbord of protein for predators and a boost of phosphorus and nitrogen for plant life through the trillions of decaying insect carcasses. According to a 2005 study, cuckoos produce more offspring in the years after cicadas emerge, while other birds such as crows appear to fly away from cicadas, another ecological mystery.

If you’re out during this year’s insect emergence and your dog or toddler happens to swallow one to three cicadas, don’t worry, said Maureen Turcatel, insect collection manager at the Field Museum in Chicago. Cicadas do not bite or sting, and they are completely edible.

“It’s going to be loud,” Tecatel said, “especially with the 13- and 17-year cicadas that are showing up in Illinois, it’s going to be a once-in-a-lifetime experience.”