Have you heard about the impending cicada-pocalypse? In May, periodical cicadas, which only emerge once every 13 years, will be crawling out of the ground across the southeastern U.S.
So What?
Perhaps you’re thinking, “I see cicadas every year. What’s the big deal?” Those cicadas you see every summer and fall are annual, or dog-day, cicadas, which emerge on an annual basis.
Periodical cicadas are more special. They are unique to eastern North America and found nowhere else in the world. They only emerge from the ground every 13 or 17 years, depending on their brood. Broods are separate populations of cicadas that emerge on the same cycle.
Brood XIX (“nineteen”), also called the “Great Southern Brood,” are 13-year cicadas set to emerge across the Southeast this year. Small areas throughout central Illinois will see a dual emergence of Brood XIX and Brood XIII (“thirteen”). The last time these two broods’ emergence matched up was in 1803, when Thomas Jefferson was president!
In Georgia, we will see a solo emergence from Brood XIX, but it’s still pretty cool. Just because periodical cicadas only appear aboveground every 13 or 17 years doesn’t mean they don’t exist in the interim. In fact, they’re alive that whole time, tunneling underground in their nymph (juvenile) stage and feeding on roots of hardwood trees.
Cicada Life Cycle
On May nights, the cicada nymphs use their claw-like front legs to tunnel up to the soil surface. The nymphs immediately find the closest tree or shrub (or other vertical surface) and start climbing up, up, up. Most will stop within the first ten feet, latch onto the bark and begin to molt. First, they split their exoskeleton down the back, then lean backwards and squeeze their new, adult body through the fissure. They hang belly up for a while and use gravity to help their wings unfurl. Over several hours, the cicada pumps hemolymph (insect “blood”) into its expanding wings until they are full size. Meanwhile, the exoskeleton cures, hardens and develops its bright colors.
Millions of individual cicadas will emerge like this over the next several weeks, and scientists still don’t know how they accomplish this amazing synchronicity.
After the wings harden, the cicada can fly up into the tree canopy and begin its ultimate objective: mating! The buzzing you hear is a mating call made by males as they try to lure in females. These deafening calls can reach up to 90 decibels, or as loud as a lawnmower. Once a pair deem each other suitable, they mate.
The female uses a serrated structure called an ovipositor to saw small slits along the tips of branches, where she lays her eggs. The adults die soon after and will all be gone by June. The eggs remain inside the protected crevices for six to ten weeks until the new nymphs hatch. They drop down to the ground and tunnel into the soil to begin their 13-year-long development. Thus, the cycle continues.
Because of this huge chunk of time they spend underground as nymphs, periodical cicadas actually have the longest development time of any insect species in North America. Talk about late bloomers!
Are Cicadas Good?
Cicadas are great for our ecosystems. Their tunneling aerates our native soils, and the decaying bodies of the deceased adults act as a natural fertilizer.
Not to mention the food source they provide. All these insects emerging at once is a bumper crop for predators. Nymphs and adults are tasty morsels for birds, fish, deer and other wildlife. Even dogs will eat them and may vomit if they binge too many (“too much roughage at one time,” says University of Georgia entomologist Nancy Hinkle). Still, there are more cicadas than our predators can consume, so some survive to sustain the population.
It’s worth noting that cicadas are not a threat to us or our pets. They are not poisonous, don’t bite, don’t transmit diseases and won’t feed on crops. Egg laying by the females may cause aesthetic damage to branch tips, but this is not likely to harm your trees.
Where to Find Them
Finding periodical cicadas can be a guessing game. In the Atlanta area, the US Forest Service says we may see Brood XIX in Fulton and Cherokee Counties. Surveys done by UGA entomologists during the 2011 emergence reported them in Fayette and Coweta counties.
Regardless, you will only find them in hardwood forests that have not been disturbed in at least 13 years and likely longer. Look for mature forests with minimal soil disturbance that are relatively close to a stream or creek. The app iNaturalist is a great way to check if others in your area have reported seeing any.
If you do see a cicada, how do you know if it’s the periodical type? Periodical cicadas are mostly black with red eyes and orange-tinted wings, while annual cicadas are green with black eyes. Dr. Hinkle makes it even simpler: “Any cicada you see before June is a periodical cicada; any cicada you see after June is an annual cicada.”
If you happen to see one, note the date and location, and take a photo! Report your observations on iNaturalist, and send your photos to your local Extension agent for good measure. If you live in Fulton County, I am anxiously awaiting your email…
Contact Your Extension Agent
Gabrielle LaTora
Agriculture and Natural Resources Agent
UGA Extension Fulton County
gabrielle.latora@uga.edu
404-613-7670
