BY CLEMSON COOPERATIVE EXTENSION
Every 13 years, a big event happens: the mass emergence of the longest-living insect in the United States — the periodical cicada. They last appeared in South Carolina in 2011. Unlike the annual cicadas, which emerge in mid-summer every year, periodical cicadas spend many years as nymphs living in the soil feeding on the roots of trees, which does not seem to cause any tree health issues.
Obvious damage to trees is done by the female as she deposits eggs into twigs, which eventually causes a symptom called flagging. This can be alarming but not a real concern for the long-term health of the tree.
In South Carolina, the emergence is projected to be in many Upstate counties and counties along the Savannah River basin down to Aiken County including Oconee, Anderson, Abbeville, Greenwood, McCormick, Edgefield, Saluda, Lexington, Newberry, Union, Cherokee, York, Chester and Lancaster counties.
The 13-year cicada brood XIX is what is prominent in the South. Emergence in this area usually happens late April into May. Over a period of a week or two, the nymphs crawl out of the ground and up the trunks of trees or other vertical surfaces. They molt one last time to emerge as a winged adult from their nymphal “skin” or exoskeleton. You will commonly see the cast skins attached to tree trunks. Cicadas are harmless to people despite their large size. They are very clumsy fliers and may fly into you, but they are not trying to attack you in any way.
About a week after emergence, they begin flying around to find their mate. Male cicadas sing to attract females for mating purposes, and their sheer numbers can make a deafening noise. There can be as many as 1.5 million cicadas emerging per acre — as much as 30,000 to 40,000 emerging from under a single large oak tree. The adults live only for a few weeks, and after about a month, they will have disappeared as mysteriously as their arrival.
All the periodical cicadas don’t emerge in the same year. There are 15 present-day broods in the United States. Eleven of these broods have the 17-year cycle, and four have the 13-year cycle. Broods are identified by Roman numerals. Brood XIX is one of the largest broods in the country, covering the greatest geographic area.
For more information, see www.cicadamania.com.
The periodical cicadas that are about to infest two parts of the United States aren't just plentiful, they're downright weird.
These insects are the strongest urinators in the animal kingdom with flows that put humans and elephants to shame. They have pumps in their heads that pull moisture from the roots of trees, allowing them to feed for more than a decade underground. They are rescuers of caterpillars.
And they are being ravaged by a sexually transmitted disease that turns them into zombies.
PUMPS IN THE HEAD
Inside trees are sugary, nutrient-heavy saps that flow through tissue called phloem. Most insects love the sap. But not cicadas - they go for tissue called xylem, which carries mostly water and a bit of nutrients.
And it's not easy to get into the xylem, which doesn't just flow out when a bug taps into it because it's under negative pressure. The cicada can get the fluid because its outsized head has a pump, said University of Alabama Huntsville entomologist Carrie Deans.
They use their proboscis like a tiny straw - about the width of a hair - with the pump sucking out the liquid, said Georgia Tech biophysics professor Saad Bhamla. They spend nearly their entire lives drinking, year after year.
"It's a hard way to make a living," Deans said.
GOING WITH THE FLOW
All that watery fluid has to come out the other end. And boy does it.
Bhamla in March published a study of the urination flow rates of animals across the world. Cicadas were clearly king, peeing two to three times stronger and faster than elephants and humans. He couldn't look at the periodical cicadas that mostly feed and pee underground, but he used video to record and measure the flow rate of their Amazon cousins, which topped out around 10 feet per second.
They have a muscle that pushes the waste through a tiny hole like a jet, Bhamla said. He said he learned this when in the Amazon he happened on a tree the locals called a "weeping tree" because liquid was flowing down, like the plant was crying. It was cicada pee.
"You walk around in a forest where they're actively chorusing on a hot, sunny day. It feels like it's raining," said University of Connecticut entomologist John Cooley. "That's their honeydew or waste product coming out the back end ... It's called cicada rain."
GOOD FOR CATERPILLARS
In the years and areas where cicadas come out, caterpillars enjoy a cicada reprieve.
University of Maryland entomologist Dan Gruner studied caterpillars after the 2021 cicada emergence in the mid-Atlantic. He found that the bugs that turn into moths survived the spring in bigger numbers because the birds that usually eat them were too busy getting cicadas.
Periodical cicadas are "lazy, fat and slow," Gruner said. "They're extraordinarily easy to capture for us and for their predators."
ZOMBIE CICADAS
There's 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," Cooley said. "This is a sexually transmitted zombie disease."
Cooley has seen areas in the Midwest where up to 10% of the individuals were infected.
The fungus is also the type that has hallucinatory effects on birds that would eat them, Cooley said.
This white fungus takes over the male, their gonads are torn from their body, and chalky spores are spread around to nearby other cicadas, he said. The insects are sterilized, not killed. This way the fungus uses the cicadas to spread to others.
"They're completely at the mercy of the fungus," Cooley said. "They're walking dead."
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