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Cicadas have developed an amazing strategy for growth, survival, reproduction, and overcoming predation by...doing nothing. They do nothing for years (except sip at the juice excreted from root structures) before emerging in huge, simultaneous swarms.

The swarm is so huge that predators can't consume even a fraction of it, but so rare that predator populations can't sustain themselves between emergence events. Clever little things!

 Introduction


Sometimes I wish I could just crawl into a hole somewhere and just not do anything for like fifteen years. Very few humans are ever able to do this, Lauryn Hill and the United States Congress  being notable exceptions. But! If you live in the eastern United States you're about to meet one of the few creatures on earth that can do this. Cicadas are insects that spend the vast majority of their lives underground biding their time until they surface in huge, noisy, red-eyed swarms. When they emerge, they number in the billions taking over entire forests and suburbs causing car accidents and ruining more picnics and outdoor weddings than I care to think about. They are so weird and appear so rarely that we still don't understand very much about them. But we do know that they've managed to turn a lazy low profile lifestyle into one of Earth's greatest evolutionary success stories. And they're coming.

(Into music)

 Cicada Species          


Sometimes people mistake locusts for cicadas because locusts are also big, noisy, summer bugs. But cicadas are their own family of plant-sucking insects that includes more than two thousand species. Some species known as annual cicadas, live underground for just two to eight years, and can be found all over the world. Different populations of these species appear at different times, so you might run across them in any given summer. But what America is bracing for right now is another kind. Periodical cicadas. They are only found in the United States and they emerge every thirteen or seventeen years and unlike annual cicadas theses species consist of just a few but enormous populations called broods. The broods' life cycles are synchronized so that they all emerge at the same time. There are fifteen known broods, each assigned a number, and this month Brood Two, also known as the east coast brood is going to emerge seventeen years after they were born.                     

 Underground Puberty


Back in 1996 brood two hatched from their eggs as nymphs, basically miniature versions of their adult selves. After hanging out for a few weeks that summer, maybe taking in the Olympics in Atlanta or talking about whether Bill Clinton would be reelected, the nymphs dug 30 centimeters or so into the soil, and got comfortable. For the next seventeen years they just sucked nutrients from nearby roots and matured very, very slowly in isolation. Basically it was like puberty, except in a burrow instead of a bedroom plastered with One Direction posters and with root juice to eat instead of pizza bagels. Now after all those years, later this month a hormone trigger will snap the cicadas out of their torpor, they'll crawl to the surface, quickly go through one final molt to emerge as adults. Then there's just two things left to do; have some sex and die.

 What They Do


Males cluster in trees and make loud buzzing mating calls in unison known politely as choruses. These obnoxious love songs have been measured at more than a hundred decibels, louder than a lawn mower or a motorcycle engine.

(Plays cicada sounds)

But they do the trick. Females respond, and after mating they lay their eggs on a low lying branch before both adults die. In about four weeks the eggs will hatch, and the whole thing starts over again. Now this may all sound fruitless but the fact is the cicada life cycle is perfectly suited to doing the two and only two things that evolution demands of us; surviving and reproducing. First of all, cicadas spend ninety-eight percent of their lives underground, protected from the elements and predators, which is partly why they live longer than any other insect in North America. But even more awesome is how cicadas have harnessed the power of the swarm. Broods can be so huge that as many as 1.5 million individuals can occupy a single acre. So even though the bugs themselves are big and slow, the brood can survive easily, because there are just too many of them to eat. This little evolutionary trick is known as predator satiation. Predators can't wipe you out when they are already full. They just don't have room inside of them.      

 Bird Populations


In fact, scientist have found that cicadas numbers are so overwhelming that they can actually manipulate the populations of the birds that eat them, to the cicadas' advantage. In 2012 a USDA study found that birds like cuckoos and woodpeckers experience huge spikes in numbers after cicadas emerge. But the spikes are so big, that three years later the populations crash, just in time for the next brood to emerge. The trick for the cicada is to show up when the bird populations are at their smallest. I mean if you're only going to do one thing every seventeen years, you might as well make it count, right?

 Closing


Thanks for watching this episode of SciShow News; for people on the east coast of the US enjoy your noisy summer. If you have any questions or comments or suggestions for us, we're on Facebook and Twitter and down in the comments below. And if you want to keep getting smarter with us here at Sci Show, you can go to Youtube.com/scishow and subscribe.