This year, cicadas are vying for the song of the summer. After 17 years underground, billions of the bugs are scheduled to emerge across the eastern U.S. around early May.
Millions are likely to screech their love songs from the treetops in Kentucky, which sits squarely in the middle of the geographic range of the great eastern brood spanning from New York and Michigan down into Georgia, said Jonathon Larson, extension entomologist with the University of Kentucky.
Unlike the annual cicadas known for providing the soundtrack to a sunset in the dog days of summer, this year’s periodic cicadas belong to Brood X.
Historical records indicate Brood X used to be wider ranging in the state, but entomologists expect this year the brood will appear along the Tennessee border and Ohio river counties west of Cincinnati, according to research from the University of Kentucky College of Agriculture.
Annual cicadas are green, black and brown and appear in two to three-year cycles. Periodical cicadas like Brood X, on the other hand, have black exoskeletons, bulging red eyes, needles for mouths (they all have needle mouths) and wings that fold tent-like over their bodies.
They’re not as bad as they might sound: They don’t bite or sting. The adult cicadas spend most of their time in trees, but with the sheer volume expected people might see them flying into windows, overrunning yards, clogging storm drains and generally playing their music too loud, according to the U.S. Department of Agriculture. They’re mostly harmless insects though they can damage young trees, causing problems for tree nurseries and orchards, Larson said.
The three species to emerge this year hatched in 2004 and have spent the last 17 years below ground as nymphs, developing in tree roots and feeding on their sap, Larson said. The cicadas count the seasons with the ebb and flow of the tree sap, emerging after either 13 or 17 cycles.
And while the thought of creatures with bulging red eyes emerging from the earth after 17 years sounds like something out of a horror movie, Larson sees it more like a Shakespeare play.
A Life Cycle In Three Acts
The mature nymphs emerge when the soil temperature reaches 64 degrees at a depth of about eight inches. They crawl out of the soil, sometimes leaving behind mud chimneys, then climb onto a convenient vertical surface to molt. This is mostly likely to begin around late April and early May coinciding blooming irises, Larson said.
After quite literally shedding their skin, the adult males set out to climb atop a tree, like an oak, ash or a hickory, and begin to play the song of their people.
“One is calling and the other cicadas will hear the call,” Larson said. “As they start to gather they can make that bigger song, which then recruits the female.”
Cicadas are percussionists. To make sound, the males flap membranes on the sides of their bodies making a click that reverberates in their abdomen, which is mostly hollow. They can produce four shrill, grindy calls — a call to attention, courtship, distress and a chorus that encourages other males to join in the same tree and increase their volume — and their chances of mating, he said.
Larson said researchers have recorded cicadas at over 100 decibels, comparable to the sound of a chainsaw or a leaf blower.
But after just about a month living, singing, and mating as an adult cicada, they die.
“It’s almost like Romeo and Juliet or something. Everybody comes out, has a good time and then dies… it’s just this weird natural phenomenon and we don’t see it like this anywhere else in the world really,” Larson said.
In terms of ecosystems, the bugs are basically a bumper crop for every animal that doesn’t feed solely on plants, Larson said. Foxes, birds, squirrels, pets and snakes are among those to indulge in the protein-rich bounty.
People can eat them too. Larson says historical records show Native Americans recorded cicada recipes. More recently, he’s heard of cicada barbecues, and although he’s not had the occasion to eat one himself, Larson says they have a nutty, walnut flavor— or as one account put it, “piney shrimp.”
Cicadas and Climate Change
Cicadas “literally put all their eggs in one basket” and there’s a lot that can go wrong in a 17-year-long development cycle, he said. From cutting down trees to paving over a cicada’s planned escape route, urbanization can make life more challenging for these insects.
Climate change compounds it further. In Kentucky, climate change is making the state warmer, and generally wetter, but those warming temperatures also bring about more extreme weather including more droughts and more floods. Unseasonable temperature changes and weather events can affect the insects.
Larson said it’s possible it could lead different parts of the brood to emerge at different times, but it’s complicated. Entomologists have recorded so-called “early risers” that emerge before they’re supposed to as well as “stragglers” that appear afterwards. In the end, it’s possible that could also help them become more resilient so that if any one brood is wiped out, another could still live on.