Trillions of bizarre marvels of evolution, the red-eyed periodical cicadas that have pumps in their heads and jet-like muscles in their backs, are poised to emerge in numbers not seen in decades, even centuries.
Emerging from the ground every 13 or 17 years, with a collective song as loud as jet engines, periodical cicadas are the queens of nature’s calendar.
These black, beady-eyed insects differ from their greener-hued cousins that emerge every year. They remain buried year after year, until they rise to the surface and take over a landscape, covering houses with their exoskeletons and making the ground crusty.
This spring, an unusual double dose of cicadas is poised to invade some parts of the United States.
“Periodical cicadas are not subtle,” said John Cooley, a cicada expert at the University of Connecticut.
If you’re fascinated by the upcoming solar eclipse, cicadas are weirder and bigger, said Saad Bhamla, a biophysicist at Georgia Tech.
“We have trillions of these amazing living organisms coming out of the Earth, climbing trees and it’s a unique experience, a sight to see,” Bhamla said. It’s as if an entire alien species lives beneath our feet and, some years, comes out to greet us. »
Sometimes confused with voracious, unrelated locusts, periodical cicadas are more of a nuisance than they cause biblical economic damage. They can harm young trees and some fruit crops, but this phenomenon is not very widespread and can be avoided.
The nation’s largest geographic brood ― called Brood XIX and appearing every 13 years ― is about to cross the Southeast, having already created countless boreholes in Georgia’s red clay. This is a sure sign of the upcoming occupation of cicadas. Cicadas emerge when the ground warms to 17.8 degrees Celsius, which is happening earlier than before due to climate change, according to entomologists. The insects start out brown, but become darker as they grow.
Soon after these insects appear in large numbers in Georgia and the rest of the Southeast, cousins of the cicadas, which appear every 17 years, will flood Illinois. This will be brood XIII.
“You have a very widespread brood, brood XIX, but you have a historically very dense and abundant brood in the Midwest, brood XIII,” said Mike Raupp, an entomologist at the University of Maryland.
“And when you put those two things together, you have more cicadas than anywhere else at any time,” said Paula Shrewsbury, an entomologist at the University of Maryland.
These hidden cicadas are only found in the eastern United States and a few tiny other places. There are 15 different broods that come out every few years, on cycles of 17 and 13 years.
The numbers that will come out this year ― an average of one million per acre over hundreds of millions of acres in 16 states ― are staggering. Hundreds of trillions, even quadrillions, according to Mr. Cooley.
An even larger adjacent joint emergence will occur when the two largest broods, XIX and XIV, emerge together in 2076.
According to Mr. Cooley and several other entomologists, the origin of some of the astronomical numbers of cicadas can probably be attributed to evolution. Fat, slow and tasty, periodical cicadas make an ideal meal for birds, said Mr. Raupp, who eats them himself. “But there are too many for them to be eaten to extinction,” he said.
“Birds from all over the world are going to enjoy it. Their bellies will be full and, once again, the cicadas will emerge triumphant,” Raupp said.
The other way cicadas use numbers, or mathematics, is in their cycles. They stay underground for 13 or 17 years, two prime numbers. These large, odd numbers are likely an evolutionary trick to prevent predators from relying on predictable emergence.
Cicadas can cause problems for young trees and nurseries when their mating and nesting strains and breaks branches, Shrewsbury said.
Periodical cicadas seek out vegetation surrounding mature trees, where they can mate and lay eggs, then go underground to feast on the roots, explained Gene Kritsky, a biologist at the University of Mont-Saint-Joseph and a specialist des cicadas, who wrote a book on this year’s double emergence. This makes American suburbs a “periodic cicada paradise,” he said.
The eardrums can be strained when all those cicadas gather in those trees and start singing in chorus. It’s like a singles bar, with males singing to attract mates, each species having its own mating call.
Mr. Cooley wears hearing protection because the noise can be very loud.
“The decibels are around 110,” he explains. It’s like putting your head next to a jet plane. It’s painful. »
Mr. Kritsky imitates the male by singing “ffaairro” (his tone rises), “ffaairro”.
“She flaps her wings,” says Kritsky. He’s getting closer. He sings. She flaps her wings. When he gets really close, he has no space, he goes ffaairro, ffaairro, ffaairro, fffaairo. »
Mating is then consummated, with the female laying eggs in a groove in a tree branch. The cicada nymph falls to the ground, then digs underground to reach the roots of a tree.
Cicadas have the particularity of feeding on the xylem of the tree, which transports water and certain nutrients. The pressure inside the xylem is lower than outside, but a pump in the cicada’s head allows the insect to extract from the tree the liquid it could not have evacuated otherwise, says Carrie Deans, an entomologist at the University of Alabama in Huntsville.
These insects are the most powerful urinators in the animal kingdom, with outputs that put humans and elephants to shame. They have pumps in their heads that draw moisture from tree roots, allowing them to feed for more than ten years underground. They are caterpillar rescuers.
And they are ravaged by a sexually transmitted disease that turns them into zombies.
Pumps in the head
Inside trees are sweet, nutrient-rich saps that circulate in a tissue called phloem. Most insects love this sap. But not cicadas: They prefer tissue called xylem, which carries mostly water and some nutrients.
And it is not easy to penetrate the xylem, which does not flow when an insect enters it, because it is under negative pressure. According to Carrie Deans, an entomologist at the University of Alabama in Huntsville, the cicada can access the liquid through its oversized head with a pump.
It uses its proboscis like a tiny straw ― the width of a hair ― and the pump sucks up the liquid, explained Saad Bhamla, a professor of biophysics at Georgia Tech. They spend almost their entire lives drinking, year after year.
“It’s a tough way to make a living,” Mr. Deans said.
Go with the flow
All that watery liquid should come out the other end. And that’s the case.
In March, Mr. Bhamla published a study on the urine output of animals around the world. The cicadas were clearly the strongest, urinating two to three times louder and faster than elephants and humans. He couldn’t observe the periodical cicadas that primarily feed and urinate underground, but he used video to record and measure the flow rate of their Amazonian cousins, which reached about three meters per second.
They have a muscle that pushes waste through a tiny hole, like a jet, Bhamla explained. He said he learned this when, in the Amazon, he came across a tree that locals called a “weeping tree” because the liquid flowed out, as if the plant was weeping. It was cicada urine.
“You walk through a forest where cicadas sing in chorus on a hot sunny day. It feels like it’s raining, said John Cooley, an entomologist at the University of Connecticut. It’s their honeydew or waste that comes out the back… It’s called cicada rain. »
Good for caterpillars
In years and regions where the cicadas come out, the caterpillars get a respite.
Dan Gruner, an entomologist at the University of Maryland, studied the caterpillars after the cicadas emerged in 2021 in the mid-Atlantic. He found that the insects that turn into moths survived the spring in greater numbers because the birds that usually eat them were too busy catching cicadas.
Periodical cicadas are “lazy, big and slow,” Gruner said. They are extraordinarily easy to capture for us and for their predators. »
Zombie Cicadas
There is a deadly sexually transmitted disease, a fungus that turns cicadas into zombies and causes their private parts to fall off, Cooley said.
It’s a real problem that “is even stranger than science fiction,” he added. It is a sexually transmitted zombie disease. »
Mr. Cooley saw areas in the Midwest where up to 10% of individuals were infected.
The mushroom is also the type that has hallucinatory effects on birds that eat them, Mr. Cooley recalled.
This white fungus takes over the male, its gonads are torn from its body and chalky spores spread to other nearby cicadas, he explained. The insects are sterilized, but not killed. The fungus thus uses the cicadas to spread to others.
“They are completely at the mercy of the fungus,” Cooley said. They are walking dead people. »