They’re ba-a-ack. Those noisy cicadas with their bright red eyes and dark bodies soon will emerge again in Missouri and Illinois after years underground, poking holes in the soil starting in mid-May.
These periodical cicadas, which differ from the larger, greenish annual variety, aren’t harmful to people and pose little threat to trees, which they can cover by the thousands. But their characteristic “singing” can be loud enough to drown out even indoor air conditioners.
This year brings a cicada double-whammy: both the 13-year and 17-year broods will come out in parts of Missouri and Illinois at around the same time. But luckily, they aren’t expected to overlap. Kansas City and the western part of the state will see (and hear) the 17-year varieties, while southeast Missouri and southern Illinois will be visited by the 13-year species.
Singing in St. Louis?
Still, experts seem to differ on whether the St. Louis region will see much of these buzzing broods.
Dan Zarlenga, St. Louis regional media specialist for the Missouri Department of Conservation, said the emergence will be “uneventful” for our area. Even though the 13-year cicadas’ range spans from Illinois to Louisiana, the cicadas won’t necessarily appear in all parts of the emergence area. He expects the furthest north they’ll go is around St. Genevieve and maybe southern Jefferson County. The more southern parts of Illinois, including near Carbondale, will also be abuzz with the cicadas' song.
But Chris Dietrich, curator of insects and state entomologist at the Illinois Natural History Survey, said it’s possible the St. Louis region and its Illinois neighbors in Madison and St. Clair counties will see some of the 13-year cicadas.
“It will occur on both sides of the river; it just sort of depends,” he said. “The cicadas require forest habitats, so they are not found out in open areas or areas that have been paved, or where the trees have been removed, so they’re really going to be restricted to areas where there is natural forest.”
Once in a century
Zarlenga notes this will be the only time this century that two broods emerge in Missouri at the same time for a double dose of cicadas. For his part, Dietrich said he’s interested to learn what might happen if members of these two broods mated and whether their offspring would adopt a 13- or 17-year lifestyle.
Zarlenga explained that these long underground lifestyles are part of a “unique survival strategy.”
“They emerge by the thousands for a brief period of time and they basically do this to overwhelm their predators,” he said. “Insects are at the bottom of food chain, so a lot of things eat them. But when they come out in so many numbers like that, the predators are just overwhelmed and oversaturated with food. So they can't get to them all, so enough of them survive to carry on their next generation.”
That’s where that buzzing sound comes in: it’s a mating call to attract the ladies. Male cicadas join together in choruses to “sing” by rubbing together and vibrating plate-like structures in their abdomens called tymbals. Dietrich said they use big air sacs in their abdomens to serve as an “amplification chamber.”
“Interestingly, if you listen carefully, there are actually four different species – each has a different call,” Dietrich said. “There are different species present in these big groups. They all look similar in coloration and structure, but we can tell they are actually different species because they have these distinctly different calls.”
Annoying, but necessary
While Dietrich said some people will find the cicadas chorus annoying, they should be comforted that it won’t be around for long.
“You just have to keep in mind that it only lasts for a month or so, then they won’t be back for 13 years, so it’s a temporary nuisance,” he said.
Plus he notes that these noisy periodical cicadas do serve an important purpose.
“A good healthy cicada population is a good indication of a healthy forest, “ he said. “They don’t really occur in places where the forest has been removed. They are spending most of their time underground feeding on roots of plants; they actually suck the sap out of the roots of trees. And of course, if you remove the tree, that's going to remove the cicada population.”
By the end of June, these cicadas and their loud buzzing will be gone – just in time for the softer, ebb-and-flow hum of annual cicadas to take over for the rest of the summer.
