This spring brings an unusual biological spectacle to the USA: a double cicada invasion. Billions of insects will populate parts of the country, with some experts predicting at least a trillion noisy cicadas by June.
Harmless Insects
For insect haters, it’s a nightmare, even though the cicadas are harmless. Recognizable by their red eyes, these cicadas have waited a long time for their emergence. Their nymphs, comparable to larvae in other insects, have been buried for many years. They climb out of the ground at night in spring once the soil temperature reaches around 64 degrees Fahrenheit.
Close to the Noise Level of a Jet Engine
After emerging, the nymphs shed their outer skeletons—black chitin shells—and inhabit the trees. Male cicadas of the genus Magicicada then begin their deafening calls to attract mates.
“In areas with high concentrations, when all the males are calling simultaneously, it can reach up to 110 decibels, close to the noise level of a jet engine,” explains entomologist Floyd Shockley from the Smithsonian National Museum of Natural History in Washington. “In such areas, I often use earplugs because it’s near the level where hearing damage can occur.”
Experts compare the sound of a single male cicada to the noise of a lawnmower or a motorcycle.
Last Seen 221 Years Ago
This year is particularly significant because there will be two massive swarms appearing at the same time, says the insect researcher. This combination, including a likely small geographic overlap of the swarms, last occurred 221 years ago, in 1803. “No one alive today will experience this again,” emphasizes Shockley.
The largest swarm of periodical cicadas, known as Brood XIX (19), has been underground for 13 years, while Brood XIII (13) has been underground for 17 years. Back then, George W. Bush was still president, and 2007 was also the year the first iPhone was released. Scientists aren’t sure why cicadas adhere to specific emergence cycles.
Scientists Expect Trillions of Cicadas
Shockley expects that over a trillion cicadas will emerge in the 17 affected states from April to June, which is more than 1,000 billion. “It will definitely be more than a trillion, possibly several trillion.”
Researchers at the University of Connecticut also predict multiple trillions of cicadas this year. The insects will primarily settle in forested areas, less so in agricultural fields or urban green spaces.
If one assumes about a trillion cicadas, and each insect is about an inch long, they would form an almost endless chain if lined up. “It would stretch to the moon and back several times,” estimates Shockley.
The Spread of Brood XIX
The last major cicada wave occurred in 2021 with the emergence of Brood X. This year, the first large swarms appeared in late April in southern states such as Mississippi, Alabama, and Georgia, as the soil warmed up with spring temperatures.
In May, Brood XIX, also known as the Great Southern Brood, will spread northward and toward the East Coast. By June, it is expected to fully emerge in Illinois in the northern United States. In the southern part of the state, Brood XIX will spread, while in the northern half and adjacent states, swarms of the smaller Brood XIII, also known as the Northern Illinois Brood, will emerge.
In some areas, experts estimate that more than a million cicadas could emerge on a space the size of half a football field. “In parts of Chicago, when Brood XIII last emerged, they had to use shovels to clear streets and sidewalks of dead cicadas,” Shockley recalls.
Dead Cicadas as Fertilizer and Bird Food
Cicadas, which primarily feed on plant sap, are not comparable to a biblical locust plague. During their short six-week lifespan after emerging, they do not ravage crops or devastate landscapes and gardens. On the contrary, when adult cicadas die en masse, their bodies fertilize the soil. “It’s good for the trees,” emphasizes Shockley.
Cicadas are poor fliers and often fall to the ground, providing abundant food for birds, squirrels, and other animals. Many will be eaten, but their survival strategy relies on their sheer numbers.