I just spent three months in southeastern Pennsylvania, visiting family. One day while raking leaves, I noticed lots of little holes in the ground – perfect little circles, like bullet holes, all through the woods, even underneath the leaves. And in some places there were also what looked like miniature earthworks — little vertical tunnels, maybe a few centimeters long, made of what appeared to be hard, dried brown mud. What on earth was going on here?

Ah, yes. I hadn’t realized. It’s 2021, and the 17-year cicadas were back!

At first I was looking forward to the experience – the first time I encountered them, in 1971, I was too young to have much interest. In 1987 I was in California. In 2004 I’d flown back from Europe after they’d already hatched. So this would be the time I could observe at least part of their lives, from nymphs through fully mature creatures. I also remembered that they were loud.

Well, loud they certainly were.

The 17-year cicada starts its life as an egg, deposited in a slit that its mother has made near the end of a tree branch. The ends of the tree branches turn brown (this is called “flagging”), die and eventually fall to the ground, allowing the tiny, newly hatched worms to burrow into the ground and stay there for 17 years, living off tree roots and probably working off the trauma from that long fall.

When the time is right, the cicadas nymphs emerge from the ground in waves over several days, crawling up the barks of the trees in the evening twilight.

They seem to have their own individual reasons for stopping their upward march where they do – some get to the end of a fern frond or a bush, and that’s that. But some stop just a few feet up a very tall tree, while others continue on 100 feet further. When they stop, they attach themselves to whatever they’re climbing – tree, frond, fence, side of house – and begin their final metamorphoses into fat, flying insects. A few days later they emerge from their dead shells and buzz off into the trees to look for mates.

The males, according to Wikipedia, congregate in choruses to entice females. The sound can be unnerving. It’s like something out of science fiction, high and eerie, like spaceships landing, and at peak periods they “sing” through the day and in the wee hours of the night.

But cicadas only live for a couple months, and so by July this entomic Woodstock comes to an end. Their noise grows fainter as more and more of their corpses collect on driveways and lawns. They’d found mates, made slits in trees to lay their eggs, and died. And the cycle beings again.