“…to Junior’s mind, there had always been cicadas. But sometime, long before he could remember, he’d been on his father’s hip, looking up into a tree at a cicada for the first time—for the very first time; that buzzing saw had always been there, but to know where it came from—to see the frantic flutter of cicada wings—to know the why, the how of something that is—What’s that buzzing noise out there?” ~ Children of Promise
By mid-May, the cicadas in Cades Cove, GSMNP, were loud enough to make visitors ask if there was a factory in the area. Fair question. Their songs are delivered at volume, reaching up to 120 decibels, according to a Texas Master Naturalist site. As to purpose? One song is to attract females; one is to seduce them, and the last one is reserved for humans who abruptly pick them up for inspection. Seriously, the last one is a distress call. Also, when one cicada senses the approach of a predator, it sings more softly so that the threat focuses on another cicada. Yes, they don’t mind throwing one of their kind under the bus.
What Are Cicadas, Anyway?
Let me start by saying they are not locusts. Not even close. In fact, there are no locusts in North America. The last ones here survived on the eastern slopes of the Rockies and represented the Rocky Mountain species, per the Animal Diversity Web. They became extinct in 1905, so don’t be bashing cicadas by laying the locust label on them. You didn’t read anything about them in the Bible, and they don’t deserve the negativity. 😉
Cicadas are not considered destructive, though they can (and do) make tiny little slits in trees to lay eggs. Saplings may take offense. This particular insect spends most of its life underground, but it starts in trees. Here’s how it goes for periodical cicadas, starting in the middle; there’s no good place to begin:
- Adult males sing to attract females to mate. Females can’t sing, but there’s no need.
- Females lay eggs in trees.
- 6-10 weeks later, the eggs hatch. The newly hatched nymphs fall to the ground and burrow under.
- The underground nymphs feed on sap from the roots of deciduous shrubs and trees.
- As the time approaches to emerge, the nymphs build exit tunnels to expedite their rise to the surface. Their emergence is temperature dependent, requiring soil at 7-8″ deep to reach 64° F.
- Dependent on their type (13- or the 17-year), they emerge from the soil they burrowed themselves into, and they arise the same year as their burrowing peers. That’s a brood, like “class of 2025”. This brood is XIV, a 17-year periodical.
- The nymph crawls onto a tree; drops its exoskeleton and waits for its wings to harden and become stable before they’re spread. That might take 4-6 days.
The life cycle of cicadas is quite different from other insects, in part because of the time underground. Also, though, adult cicadas have a short time on the topside. They die 4-6 weeks after they emerge. They take care of business, and then they’re gone.
Then History
Sadly, we have no cave drawings, but according to a University of Connecticut article, fossil evidence reflects the existence of cicadas as far back as the Late Miocene period. That’s more than 5 million years ago. However, other sources indicate they’ve been around for at least 40 million years, and they have left a mark.
We have documented examples of the cultural impacts that date back to 1500 BC, per the Smithsonian. In China, cicadas were symbols of rebirth, and it’s easy to connect those dots. When cicadas shed their exoskeletons, they begin a new phase of their lives in a winged body. In response, they carved cicadas out of jade and placed them on a deceased person’s tongue. They believed (hoped?) their loved one would escape their decaying body and achieve immortality. That’s just one example; there are many others.
Please note that despite the length of this post, the content represents only a portion of the information available. You can read as much as your cicada appetite permits by accessing the links.
Where are they found, in case you're looking?
This family of insects (Cicadidae) is found all around the world, subject to the climate. They only inhabit temperate and tropical locations. (So none in Antarctica.) However, the ones we are currently dealing with in East Tennessee are periodical cicadas, and they inhabit North America exclusively. Those I’ve seen recently are in wooded areas, but they can as easily be seen in your backyard, hanging from the leaves.
Lest you think tree leaves are required, consider that cicadas live in deserts and grasslands as well. They can use scrub in the same way trees are inhabited here. But where, specifically? Reconnect with Nature tells us there are more than 3,000 species; some sources say more than 5,000. The continent with the greatest diversity of cicadas is Australia, with 350 verified species, but researchers are confident the number is between 800-1000.
I believe this continent has only two species, the Neotibicen (annual emergence), and what we’re seeing now, the Magicicada (periodical). The latter species has both 13-year and 17-year periodicals. You may have noticed that 13 and 17 are prime numbers – why are these life cycles equal to prime numbers?
The oversimplified answer, which is the only one you’re going to get here, is that it’s a survival technique to avoid providing sustenance to multiple generations of predators. The healthier and more vigorous their predators are, the more likely they are to reproduce. Limiting frequency limits predators’ opportunities to diminish cicada populations. My Cliffs Notes are a poor substitute for the detail provided by Scientific American, which also provides a brief but illuminating video. I suggest you watch it for a better understanding.
- When cicadas shed their exoskeleton for the final time, they are as pale as ghosts. Their coloring changes as they mature.
- Cicadas’ en masse-emergence is a survival mechanism, as predators become glutted before the entire brood is consumed.
- The North Carolina Native Americans used to dig the nymphs out of the ground and fry them up in pig fat or pickle them for later. These days, they may contain high levels of mercury and may not be safe for consumption, but some cultures still consume them.
- There are as many as 1.5 million cicadas per acre in regions where broods are popping up.
- The Magicicada have wings with a special feature. If you look toward the end of the wing, there’s a little black W.
What are cicadas good for, anyway?
Like so many things (and sometimes people) who bug us, cicadas have their uses. Not only do they aerate the soil as they burrow into their disparate resting places, but they also provide nutrients as they decompose. If that isn’t enough, think of the bounty they provide the birds and mammals when they surface. It’s a veritable buffet, though it isn’t on offer for very long.
So, the next time someone tries to break line at the grocery or on I-40 and you’re questioning the reason for their existence, think of the cicada. Maybe there’s something about them–something most excellent– that you don’t know. It’s possible.
Very interesting. Wondering if they may be shy as i have only heard them sing in remote places. Also curious about their changing colors. Glad you mentioned that Locusts in US are extinct. Because as a child in the 40’s Locusts swarned our neighborhood
Have periodically heard them all my life and never considered them a pest, just the sound of summer. One and a half million per acre? Maybe we should be eating them!
Some people DO eat them. If they were fried and I didn’t know what I was eating, I might even like them.