My daughter graduated from college in 2004 and we went to her open-air graduation ceremony in New Jersey in late May of that year. It was a memorable event, not just because of the occasion but because it also coincided with the 17-year cycle for the emergence of cicadas in the eastern part of the US. This year will see the next emergence.
Billions of cicadas that have spent 17 years underground are set to emerge across large areas of the eastern US, bringing swarming numbers and loud mating calls to major towns and cities.
The periodic cicadas – bugs with strikingly red eyes, black bodies and orange wings – burrow underground as nymphs and suck fluids from the roots of plants as they grow, eventually bursting into the open as adults in mass synchronized events.
The last such event for 15 states including New York, Ohio, Illinois and Georgia occurred in 2004. The cicadas emerge in a 17-year cycle, meaning they will appear this year once temperatures are warm enough, expected to be mid-May.
“They may amass in millions in parks, woods, neighbourhoods, and can seemingly be everywhere,” said Gary Parsons, an entomologist at Michigan State University. “When they are this abundant, they fly, land and crawl everywhere, including occasionally landing on humans.”
Parsons said that while cicadas will not harm people, pets that gorge on them may become ill. It is thought that long underground development helps cicadas survive predators, as their huge and synchronized arrival provides protection in numbers.
The noise made by the enormous swarms will be noticeable, however, with males emitting mating calls that can reach 100 decibels, the same sound as standing next to a motorcycle revving its engine. The males produce these mating “songs” by vibrating their tymbals, two rigid, drum-like membranes on the underside of the abdomen.
Experts say if people are able to forget about the noise and the surprise of surroundings covered with cicadas, they will be able to appreciate a rare wonder of the natural world.
It is quite something to behold. I had never seen or heard anything like it. In fact, I had not even heard of cicadas before being confronted by this event. Although I lived in Ohio, I only moved there in 1989, after the previous cicada explosion in 1987.
What intrigues me is the cycle of 17 years. That seems like such an odd number (pardon the pun). Insects in general live such short lives, usually measured in days and months, that having such a long gestation period seems weird.
Evolution produces some fascinating life forms.
The reason for the long interval is evolutionary: if you adopt a prime-length life cycle, you outfox all your specialist predators who don’t have the same length cycle, and if there are any that do, you can escape them by going up to the next prime and hope they can’t follow. There are also critters with 11- and 14-year life cycles, for the same reason.
I love cicadas, always have. There are cicadas that emerge on different cycles and I like them all. It is so cool that they actually spend most of their lives underground. I delight in their calls. I hope some emerge near me this spring.
As Ketil says, it’s game theory.
I called them “wheeeyoos” when I was a kid. Since I am surrounded by woods I’m expecting quite a show.
Cicadas appear in their prime
In Michigan, among other places, we have mayflies, famous for their 1-year life cycle. They spend nearly an entire year as either eggs or larvae on the bottom of a lake, then emerge as adults en masse, mate, lay eggs, and die all on the same day. Lakeside communities have to deal with the huge volume of dead mayflies, sometimes needing snow shovels to dispose of them.
I was 15 when they appeared in 1970.
Using a coffee can to collect them in, I pulled them off trees and shrubs by their folded wings and then dumped the full can in our farm pond. The ducks loved me.
A friend got “stung” by one locust when she laid her eggs in his arm.
That really hurt.
Easy way to entertain yourself and any nearby kids; grab a nymph as it crawls up a tree trunk or plant stem to molt. It’ll cling onto any sufficiently vertical surface in your house, like a window curtain, so you can just pop it there and watch the molt happen. The color changes and the inflation and hardening of the wings are a treat to behold.
Cicadas are edible, too; they’re softest just after the molt. Freeze or boil them to kill them, then cook ’em like shrimp.
I do like an animal whose only real defense is “you might get sick if you eat too much of me.” That makes them slightly less dangerous than Snickers bars.
https://castbox.fm/vb/26512445
Why 17? There has to be an evolutionary reason, but it could be long gone and it’s now a remnant of the past.
If it matched the sun’s 11 year cycle, that would make sense.
https://spaceplace.nasa.gov/solar-cycles/en/
My favorite Far Side ever:
https://imgur.com/iWEkvAp.jpg
.
I’ve also always enjoyed this cicada impersonation.
@Intransitive, 10: Just give the first five minutes of the podcast (In Our Time with Melvyn Bragg from the BBC) a listen.
We don’t know. We have an idea, and it’s to do with avoiding predators, but we don’t really know. Any explanation has to account for
(1) it’s always prime numbers
(2) different species settled on different primes.
@12: Easy! They evolved from the insect-math-nerds to decide which prime number is the best, of course. xD
#12 son
According to #1 Ketil, there are also bugs with 14 year cycles.
@Holms: citation needed.
@Holms:
Careful reading will show that Ketil was specifically talking about primes as well. Therefore, “14” must be a typo for “13”.
The other known species of prime-number cicadas do indeed have a thirteen-year cycle. I don’t know what the 11-year period is that Ketil refers to; it might not be a cicada, or it might be a misremembrance,
Looking at this map from the wiki page Owlmirror shared above…. It’s a somewhat old map, but looking ahead, there are just a couple of years (2022 and 2023) which stick out because they don’t have a periodical cicada brood emerging somewhere in the Eastern US … other than some stragglers in the off years I suppose, in addition to the annual ones. But of course, in other periods the 13-year and 17-year broods will line up differently — occasionally, there wouldn’t be any gaps for a long time, assuming those cycles don’t change.
It’s also interesting that there are twelve active 17-year broods but only three 13-year broods. Why so many of the former and so few of the latter? (Based on this site, one of each seems to have gone extinct in recent history.)
Sorry: none in 2026 either. I missed that one somehow.