Blog & News

September 6th, 2024

Surviving Cicada Season

Author: Liz Hartel, MS

Let’s talk about cicadas. With over 3,000 species, cicadas are a typical summertime occurrence for much of the world. Most cicada species are annual cicadas, meaning they emerge at various times throughout the summer every year. In the US, there are also seven species of periodical cicadas who have developed the unique evolutionary trait of emerging all at once every 13 or 17 years.

As you may have heard, 2024 was special for cicadas – the US saw a double emergence of adjacent broods of periodical cicadas. Brood XIX (aka the Great Southern Brood) is a 13-year brood stretching across the Midwest and Southern US (from Missouri through the Carolinas). Its neighbor, Brood XIII (aka the Northern Illinois Brood) is a 17-year brood spanning northern Illinois and eastern Iowa. These particular broods sync up once every 221 years – making this truly a once in a lifetime experience.

Now, dear reader, you might be wondering why I’m invested in cicadas. After all, I’m not a typical cicada predator (although some people do eat cicadas). So let me tell you a bit more about my personal experience with the 2024 emergence, and why cicadas are so fascinating.

Last year, I moved to St Louis, MO – which is within the range of Brood XIX. This is my first time witnessing a periodical emergence, and I can honestly say I’ve never experienced anything like it.

Periodical emergence is an important ecological event – both for cicada species and for predators. Cicadas are clumsy fliers with no active defense mechanisms (camouflage, flying away, and screeching are about it). Predators include birds, bears, fish, raccoons – basically anything that eats insects will eat cicadas. Even one of my indoor cats (appropriately named Gremlin) thinks they’re delicious. By emerging all at once, periodical cicadas flood the area with so many tasty cicadas that it’s impossible for predators to eat them all – thereby ensuring the survival of most of the brood. In turn, predators get an all you can eat buffet. Adorable baby raccoons (or ABRs as my husband calls them) returned to our yard several times to feast on this buffet.

There’s no ecological negative to cicada emergence. Unlike many other insects, they don’t cause damage to plants or property. Small trees and shrubs can face slight impacts if too many feed on their sap or lay eggs in them, but larger trees are completely unfazed. Small trees can be easily protected by placing a fine mesh net over them during emergence. Cicadas also don’t bite or sting (although their grippy feet feel a little uncomfortable on the skin) and are non-toxic so you don’t have to worry too much about pets. However, pets with no self-control (like my cat Gremlin) might eat too many and give themselves a tummy ache if left unsupervised.

The lifecycle of periodical cicadas is an interesting one. They spend most of their lives underground, in the nymph stage, feeding on root sap. After 13 or 17 years (depending on species), they emerge in April-May when soil temperatures reach approximately 64°F. In St Louis, in early May we started to see a few cicadas here and there. Within five days, they were suddenly everywhere – covering tree trunks, the sides of houses, and swarming through treetops.

But how do cicadas know when to emerge? Scientists believe they use the root sap to track the growth cycle of the trees they feed on. When trees bud in the spring, the sap temporarily contains more amino acids; cicadas use this change to count the number of springs that have passed. Then, when its time, cicada nymphs emerge from the ground and crawl up the nearest vertical surface to molt. The winged adults then clumsily fly around, drink sap from woody shrubs or trees, and look for mates. The males screech out their mating call, often banding together with other males to form a chorus. In St Louis, by May 18^th the cicadas got so loud we wore hearing protection when we walked our cats outside (yes, we walk our cats on leash).

Another prominent thing the adults do is urinate – up to 10 feet per second! The sap cicadas feed on is low in nutrients, but high in water content – meaning they consume A LOT of fluid. Because of their digestive system, cicadas process fluid at 300 times their body weight and urinate in a jet stream. It’s so common, it has a nickname - “cicada rain.” Between the noise, cicadas flying into my hair, and getting peed on by cicadas, being outside was pretty unpleasant by late May.

After mating, a female lay her eggs in a groove she makes in a tree limb. Then the adults die en masse, leaving the faint stench of death lingering in the air (in St Louis, this started to happen around June 1^st). Thankfully, the smell wasn’t overwhelming like decomposing mammals, but more reminiscent of fertilizer used in crop fields – likely because dead cicadas are chock full of nitrogen (the main ingredient in most fertilizers). This is just another example of how cicadas are a boon for the environment – ending their lives as nutrient-rich plant food for forest soil, gardens, trees, lawns, and wildflowers. Later, when the eggs hatch, nymphs will feed on the exposed sap and then eventually drop to the ground and burrow near the base of the tree – and the cycle begins again. All-in-all, periodical cicadas are above ground for approximately one month of their lives. And if you had just one month to live above ground, would you really live it any differently?