They're Here

The eastern U.S. is home to 15 broods of cicadas that appear on either 17- or 13-year cycles. Brood X is one of the 17-year variations. Why they wait 17 years to emerge, nobody is quite sure. One theory is that they have an “internal molecular clock” that allows them to sense the passing of time by queues in the xylem they rely on to sustain them underground.

Xylem helps water move around plants and trees, and the fluids in it contain water and nutrients. The theory goes that cicadas can gauge tree leaf out to count the years.

But it’s ground temperature that triggers their emergence from underground. Specifically, accumulated ground temperature. Once soil temperatures hit 64 degrees Fahrenheit (18 degrees Celsius), the cicadas come crawling out of their burrows to start looking for love.

Cicadas emerge as nymphs. But to get down to business, they first need to molt and shed their shells to become adults. The leftover shells can be a bit freaky, but then you could say that just about any part of cicadas’ life cycle.

Once they’ve shed their shells, they unfurl their wings and get ready for liftoff. Their exoskeletons also harden up.

A hardened exoskeleton only gets you so far in life when you max out at 2 inches (5 centimeters) in length. In a world of hungry birds and other wildlife looking for a bug snack, cicadas are prime targets.

Having a whole cicada posse is an emergent way of continuing survival of the brood. Last year’s Brood IX cicada invasion saw an astounding 1.5 million cicadas per acre emerge. While many will be picked off by predators, that’s simply more prey supply than predator demand. Individual cicadas will give up their lives early so that the brood may continue. It’s noble in a weird way. Props, I guess.

While they’re gnarly-looking bugs, cicadas pose no harm to humans. That is, as long as you’re a heavy sleeper.

To woo mates, male cicadas create a ruckus. The sound of cicadas can be nigh unbearable, even with earplugs in. The otherworldly chorus isn’t cicada yelling. Rather, it’s the result of vibrations. Allow the Chicago Botanic Garden to explain:

“Male cicadas will call females to mate by vibrating their tymbals, which are two rigid, drum-like membranes on the undersides of their abdomens. Different species of cicada produce different songs. Males respond to the calls of other males, creating a chorus of ‘singing’ cicadas that can be deafening. Females do not have tymbals and are incapable of producing the same sounds.”

Cicadas, they’re more like us than we thought.

After mating, females can lay up to 400 eggs. Those eggs hatch, and the larvae fall to the ground where they burrow in for a 17-year wait to reemerge. The adults, meanwhile, die. Poetic.

As a science journalist, you are supposed to wow your audience with facts. This is especially important now as the pandemic risk begins to wind down in the U.S., so that you, the reader, have interesting things to tell friends at a dinner party or to yell drunkenly into a stranger’s ear at the club, otherwise known as the human version of the cicada mating call. Weird facts are the difference between society and anarchy.

To ease you back into having a social life, please feel free to use these cicada facts to break the ice at future gatherings. (You may also continue to not gather socially and hang with your cat, who I am sure would also appreciate hearing these facts.)

• Cicadas are so loud, they could be fined for noise violations in Baltimore.
• Cicadas can get hopped up on a psychedelic fungus that makes their asses fall off—but they can still continue to bone even after that happens.
  
• Bob Dylan wrote a song about cicadas after being inspired by hearing them while receiving an honorary degree at Princeton in 1970 (that’s a bonus Bob Dylan fact).
• The song is “Day of the Locusts,” but cicadas are not locusts. This makes Bob Dylan a liar. I knew there was a reason I always hated him.
• Though this year’s relatively cool spring has slowed the emergence of Brood X in some places, climate change will likely mean cicada broods emerge sooner, not later. In fact, some members of Brood X emerged in 2017, four years ahead of schedule. It could eventually wreak havoc, leading to new broods.