Contributed by Isaac Smith, Principal, PPM Consultants
Each year that passes seems to bring more surprises or head-scratching events. Most of those events are driven by people and their ever-increasing irrational behavior. But every now and then there are newsworthy events that are driven by nature, and some of those are as strange as they get.
Right now, across the Eastern US, there are literally trillions, yes trillions, of cicadas emerging from the ground, taking flight, and making a ton of noise. Across the US, there are 15 broods, which are geographical groups of cicadas that each consist of up to four different species. Depending on the individual cicada species, the broods emerge on a very predictable, albeit infrequent schedule. And by infrequent, I’m referring to every 13 or 17 years. Now it’s not all that unusual for different broods to come out at the same time, but it’s rare for geographically adjacent broods to emerge together, which is what’s taking place right now. In fact, this year’s emergence is historic as it contains the 17-year Brood XIII to the north and 13-year Brood XIX to the south. In fact, these two broods haven’t emerged at the same time for 221 years!
What are Cicadas Anyway?
In the world of insects, the cicadas are known as a superfamily. They are found around the world and have more than 3,000 different species. Nearly all cicada species are annual cicadas (emerge annually), with the exception of a few of the North American species, known as periodical cicadas. These periodical cicadas are the ones making their presence known in 2024. Each time the cicadas of a particular brood emerge, the result can be something out of a cheap B movie. However, since the cicadas emerge from forested areas, they can go unnoticed by people who live in larger cities. Anyone who grew up in a rural area knows the distinct loud sound the insects make.
Cicada Lifecycle
As mentioned above, the North American cicada’s lifecycle is pretty odd. The adults emerge in either 13 or 17-year cycles to mate. The loud buzzing sound you hear if you’re anywhere in the US where this is happening is the male’s courtship call. The “singing” is produced in one of two ways. Some cicadas use a special structure called a tymbal which creates a sound when they rapidly flex and relax their abdomen, which produces the sound. When you think about it, rapid flexing of the abdomen doesn’t sound that different than what takes place by a group of teenage boys when a young lady walks by, just without the ‘singing” part.
Other cicadas rub their wings together where a series of ridges create a sound that may further be modulated by the male’s largely hollow abdomen. While yet a third variety produces no sound but rather the males and females produce vibrations that are transmitted through the tree.
In some species the males remain stationary and call to the females but sometimes several males aggregate and call-in chorus. If the male cicadas’ sweet sounds are enough to attract a female, they’ll mate and her eggs will be deposited on trees where they’ll eventually fall to the ground and hatch into nymphs that burrow into the ground and feed on tree sap for the next 13 to 17 years. And you thought your life was dull.
The periodic emergence of the cicadas is not by accident but rather a survival mechanism. The cicadas have a hard life. From the time they hatch, everything wants to eat them; while underground they are targets of ants and other invertebrates. As they grow larger, moles, armadillos, and other burrowing mammals snack on them. Once they emerge, they are a main course of birds, snakes, turtles, and even humans, yes humans. I actually saw a recipe earlier this week on Facebook for Tempura Cicadas with Sriricha Aoili; in fact, if you google cicada recipes you might be astonished as to how many people are apparently eating these things, and considering their abundance, maybe they are a good alternate source of protein. But seriously, the density of cicadas emerging is astonishing, around 1.5 million per acre. And although they have virtually no other defenses, they’ve been around for thousands of years due to a simple survival mechanism the insects employ, safety in numbers.
The overwhelming density and numbers of cicadas emerging at once is similar to a school of small baitfish that gather together and move in unison, just hoping that the predators get full before they are all eaten. Or how coral reefs reproduce by releasing massive numbers of eggs or polyps in a short period of time. There’s a high rate of mortality in many of nature’s creatures, but they all have some sort of mechanism to try and ensure their survival. Additionally, the sheer numbers of the cicadas that emerge are enough to alter the food chain for many animals in the area that switch from their general prey to focus on the cicada buffet. Regardless of whether the cicadas are eaten by another animal or die after mating, the end result is a lot of nutrients are returned to the soil, which helps the trees grow and ensures the cicadas have plenty of sap for the net 13 to 17 years underground.
Summary
In the coming weeks, if you find yourself travelling through areas of Iowa, Illinois, Michigan, Missouri, Arkansas, Louisiana, Mississippi, Alabama, Tennessee, Georgia, or the Carolinas and see some rather large insects in biblical numbers or are outside at night and hear a loud buzzing/ringing noise, you’ll probably say, “hey, that’s a cicada,” and ramble on about some of its lifecycle like I have in this article. Your friends or family will either think you’re pretty smart or some weirdo that has a fascination with big, noisy bugs, but regardless, you’ll know a little more about the insect than you did before you read this article.
Links to other articles or websites on this topic are provided below.
Active Periodical Cicada Broods of the United States (usda.gov)
Cicadas out in Alabama: Latest sightings of Brood XIX; full US map (usatoday.com)
The 2024 Periodical Cicada Emergence | Periodical Cicada Information Pages (uconn.edu)