In the late spring of 1634, pilgrims in Massachusetts seen an unbelievable sight: Millions and millions of winged, red-eyed pests arose from the ground. Not knowing better, the Puritan immigrants likened them to pestilential swarms from the Old Testament and called them”locusts.”
But they were wrong. This was the earliest written record of periodical cicadas, seven species of which emerge each 13 or 17 years from the U.S. Midwest and East Coast. This year, trillions of these insects will once more burst out of the floor and take into the trees, making loudly mating songs as they harmlessly sip tree sap.
The 2021 cicadas, called Brood X, are the largest of the 15 known periodical cicada broods. These inch-long pests will soon emerge throughout large swaths of Indiana, Ohio, Pennsylvania, Maryland, Washington D.C., as well as beyond.
Not everybody is thrilled, with many on social media fearing the shrill sounds of the cicadas, as well as their disgust overall. “If the cicadas ruin summer 2021, I will scream,” stated one Twitter user. Even now, nearly 400 years after the Puritans arrived, some Americans still mistakenly refer to this cicadas as locusts, a totally different type of insect that is known for devouring crops.
With cicadas, though, there’s nothing to dread –and witnessing such a huge arrival of pests is really a rare privilege, says Jeffrey Lockwood, an entomologist and professor of natural sciences and humanities in the University of Wyoming
“It’s a phenomenon that ought to generate awe and respect and wonder,” he says.
For one thing, the scale of Brood X is massive, a relic of a moment, until European colonization, when North America teemed with insects and other creatures. In some forests, around 1.5 million cicadas can surface in one acre. By some estimates, there might be several trillion of the pests appearing this summer, Lockwood says.
“We’ve done such a thorough job of decimating the natural world that any organism, at least any animal, that appears in these sorts of numbers–it’s wonderfully humbling,” Lockwood says. It is a reminder that people aren’t the only animal on this planet and that we need to share the space with other people, ” he says.
Richard Karban, an entomologist in University of California, Davis, says that these pests”are the herbivores of eastern forests,” more striking in number and mass compared to any other. Though we see them only every 17 decades, they’re there all the time, slowly growing underground while drinking fluids from tree roots. (Read more about why U.S. cicadas lie dormant for over a decade.)
One research estimated that the total biomass of cicadas in a specific area of forest is higher than the biomass of cattle the same area could support if it had been turned to pasture. These quotes”are the highest recorded for a terrestrial animal under natural conditions,” the scientists wrote.
“You’re taking insect biomass that’s been underground for years and then quickly moving it aboveground–and this has far-reaching positive impacts,” states Elizabeth Barnes, an entomological educator at Purdue University
Besides being a source of food for predators, the cicadas’ emergence helps move nutrients around the ecosystem, aerate the soil, and relieve predatory pressure on non-cicada insect populations, she says.
Why 17 years?
There are about 3,000 cicada species on Earth, but only seven are periodical cicadas, which are unusual in that they come out every 13 or 17 years and are almost all found in North America. But why do they choose such long time periods, which are both prime numbers?
There are several theories. One is that these periods evolved to optimally avoid predators, Barnes says. The second is that by using prime numbers, the periodical cicadas minimize overlap with other periodical cicadas, thus avoiding genetic hybridization and competition for resources.
But these theories are speculation, Karban says, as there’s currently no real way to test them.
Another unusual aspect of the insects’ behaviour is that, unlike nearly all other non-noxious insects,”they do very little to escape predators,” Karban states, which is why some call them foolhardy in the face of a hungry animal.
“Anything with a mouth is going to eat them, so it’s going to be a good year to be a bird” or another predator,” states John Cooley, an entomologist at the University of Connecticut.
The synchronized swan song of these large masses probably evolved because they overpower predators, getting so numerous that only a small proportion of their total can be eaten. (Check these out cicada recipes.)
This phenomenon, along with the loud sounds they make, is about procreation, Lockwood adds. “They’re coming out in the biggest orgy that you’ll see in your lifetime,” he says.
The least we can do is not be frightened. “They don’t sting, they don’t bite, they’re not going to try to come after you,” Barnes says. Fear of pests generally comes out of a lack of education and experience, she adds.
“I think Americans in particular are kind of trained to abhor insects–they don’t have a lot of contact with them and think of them as being dirty,” Cooley says. (Learn more: Murder hornet mania highlights risks of fearing insects.)
But Brood X’s coming is an opportunity to change this, Cooley says, by quitting to have a better look at cicadas and appreciating their lengthy, synchronized life cycles, including their short, four-to-six months of life aboveground.
People also needs to love that these insects have been around for about five million decades, about the time the ancestors of humans and chimpanzees split from one another, Cooley says.
The Brood X emergence provides hope, also, he says:”It’s an indication that the forests are healthy enough to function.”