If you haven't yet been serenaded by the unique screech of cicadas, you may soon notice the telltale sound of approaching summer. While Middle Tennessee gets its share of cicadas each year, some periodic cicadas emerge in broods, a combination of several species, every 13 or 17 years.
This year, much of Middle Tennessee will see Brood XIX, The Great Southern Brood of the 13-year cicadas. It last appeared in 2011 and is making its return this year. Next year, Warren County can expect the return of Brood XIV, a 17-year periodical cicada brood.
Emerging in early May, Brood XIX can be expected to be seen and heard for a few weeks, during which the cicadas will emit their high-pitched, shrill mating call. Following mating, the female cicada deposits eggs into slits made on twigs. This egg laying can cause damage to trees in nurseries and newly planted orchards.
Dr. Karla Addesso, associate professor and director of the Tennessee State University Nursery Research Center in McMinnville says that, other than the possible damage inflicted on trees, cicadas pose no threat to humans apart from being an annoyance.
"The only direct damage they cause is to trees when they lay eggs in twigs. They are mainly a nuisance to people," Addesso said.
An invasion of cicadas can sometimes seem a bit overwhelming simply because of their sheer numbers. "The highest density ever reported was 1 million cicadas per acre in 1956," said Addesso.
The periodic emergence in large volume is thought to be a defense mechanism. "Cicada scientists believe that emerging every 13 or 17 years in huge numbers is their defense. It is referred to as the ‘predator satiation hypothesis.’ Since the insects have no physical defenses, they overwhelm predators by emerging in such high numbers that the predators can’t eat them all. That allows the survivors to mate and lay eggs safely after the predators in the area are full," Addesso said.
While the unrelenting scream and possible tree damage are far from ideal, Cicadas do offer some benefit to adventurous eaters. "You can think of cicadas as ‘land shrimp.' Eating them is safe as long as you are not allergic to shellfish. There are a number of free recipe books online. The newly emerging cicadas are the best to eat because their shells have not yet hardened. To collect these, wait until 9 p.m., grab a headlamp, find a large tree and look for cicadas hanging upside down, emerging from their nymph skins. They will be a creamy white color," Addesso said.
For additional information about cicadas, contact the Tennessee State University Otis L. Floyd Nursery Research Center at (931) 668-3023 or visit www.tnstate.edu/agriculture/nrc/.
