Free fertilizer: After short life above ground, 17-year cicadas dying, rotting quickly

The continuous hum of Brood X cicadas, perched in the branches of trees, is coming to end, replaced by piles of insect carcasses and the smell of, well, dead cicadas.

“Rotten, but not forgotten,” said Eric Day, an entomologist at Virginia Tech. “Their short time above ground is coming to an end — they’ve done what they’re supposed to do.”

The life cycle of cicadas is a fascinating one, Day said — 17 years underground, four to six weeks above ground.

“In that four to six weeks above ground they’re mating, laying eggs in twigs. Those eggs will hatch in July,” said Day. “Then the nymphs, almost smaller than a rice grain, will drop to the ground, and burrow into the soil.”

Underground, the nymphs will have a long time before the next appearance of Brood X, in 2038.

“They’ll attach themselves to the root of a tree, and there they will remain — feeding, developing, and growing, for the next 17 years,” said Day.

And the adults will just rot — which is part of nature.

“It is a return of nutrients,” Day said. “Even though they smell bad, it is good for the trees and the like.”

For those tending flowers, fruits and vegetables: “It wouldn’t hurt if you want to rake them up and put them in your garden — free fertilizer!”

Or, you could just leave the carcasses where they fall, which will likely be around the trees in which they mated.

“They’re gonna dry out somewhat, so you will probably will be seeing those cicada carcasses pretty much the rest of the summer,” said Day. “But the smell is going to go away fairly quick — maybe a couple of weeks.”

While homeowners can either repurpose the mounds of cicada carcasses or leave them alone, Day said they’ll want to clean out rain gutters and other home systems.

“For an area with a really big emergence, and a lot of them flying around, you definitely want to check drains to make sure they’re not getting plugged up by the cicadas,” he said.

Neal Augenstein

Neal Augenstein has been a reporter at WTOP since 1997. Through the years, Neal has covered many of the crimes and trials that have gripped the region. Neal's been pleased to receive awards over the years for hard news, feature reporting, use of sound and sports.

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A cicada drives a car carrying a boat trailer in this photo staged by Scott and Ellie Kanowitz. (Courtesy Scott and Ellie Kanowitz)

A cicada rides a skateboard in this photo staged by Scott and Ellie Kanowitz. (Courtesy Scott and Ellie Kanowitz)

A cicada wears a police hat in this photo staged by Scott and Ellie Kanowitz. (Courtesy Scott and Ellie Kanowitz)

Cicadas are locked up in a police car in this photo staged by Scott and Ellie Kanowitz. (Courtesy Scott and Ellie Kanowitz)

((Courtesy Scott and Ellie Kanowitz))
A white cicada.

Cicadas swarm a D.C. flag in a Northwest District community on May 18, 2021. (WTOP/Dave Dildine)

Countless cicadas emerge from the ground in a Northwest D.C. neighborhood on May 18, 2021. (WTOP/Dave Dildine)

Cicadas on a tire in this file photo.

A swarm of cicadas collect on a garden fence along Northwest D.C.’s Reno Road, near Chevy Chase, during a mass emergence on May 18, 2021. (WTOP/Alejandro Alvarez)

Cicadas get better acquainted in Potomac, Maryland on May 20, 2021.

Dozens of cicadas dot a tree on South Utah Street in Arlington, Virginia, on May 19, 2021. (WTOP/Antonello Favaro)

Jeff Herge of Herndon, Virginia, has so many cicadas by his fence that he hesitates to walk near it. (Courtesy Jeff Herge)

Cicadas dry their wings after emerging from the ground in D.C.s Palisades neighborhood on May 10, 2021. (Courtesy Jewel Tomasula)

Three “Brood X” cicadas cling to a tree and shed their shells in D.C.’s Palisades neighborhood on May 10, 2021. (Courtesy Jewel Tomasula)

A safe spot for cicadas is found in Potomac, Maryland on May 20, 2021.

Cicadas break in their new bodies in Potomac, Maryland on May 20, 2021.

A newly-molted cicada stands beside its former self in D.C.’s Woodley Park neighborhood on May 18, 2021. (WTOP/Brennan Haselton)

An adult cicada hangs upside down just after shedding its nymphal skin, early Wednesday, May 5, 2021, on the University of Maryland campus in College Park, Md. The cicadas of Brood X, trillions of red-eyed bugs singing loud sci-fi sounding songs, can seem downright creepy. Especially since they come out from underground only ever 17 years. (AP Photo/Carolyn Kaster)

An adult cicada is seen, in Washington, Thursday, May 6, 2021. Trillions of cicadas are about to emerge from 15 states in the U.S. East. The cicadas of Brood X, trillions of red-eyed bugs singing loud sci-fi sounding songs, can seem downright creepy. Especially since they come out from underground only ever 17 years. (AP Photo/Carolyn Kaster)

A cicada nymph wiggles its front legs as it is held, Sunday, May 2, 2021, in Frederick, Md. People tend to be scared of the wrong insects, says University of Illinois entomologist May Berenbaum. The mosquito kills more people than any other animals because of malaria and other diseases. Yet some people really dread the cicada emergence, she said. (AP Photo/Carolyn Kaster)

A periodical cicada nymph clings to a tree branch on May 11, 2021 in Greenbelt, Maryland. – Some are waiting for their arrival with trepidation, others are curious what they might taste like: Americans are swapping tips on how best to weather the storm when billions of cicadas soon emerge after 17 years underground. (Photo by JIM WATSON / AFP) (Photo by JIM WATSON/AFP via Getty Images)

A robin feeds a cicada to her young. (Courtesy Jennifer Baum)

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