Name: Why Billions of Cicadas Are About to Emerge After 17 years
Uploaded: 2021-04-21T17:40:13.000Z
Duration: 5 min 25 s
Description: Thousands of YouTube videos with English-Chinese subtitles! Now you can learn to understand native speakers, expand your vocabulary, and improve your pronunciation...

Advanced passive voice

Ah, Spring 2021 is here and there are so many reasons to be excited. The flowers are blooming.

The sun is shining. The trees seem to scream at you as billions of cicadas erupt

from the soil after a nearly two-decade-long absence and sing their mating song. Just listen

to that sound of the season.  [Cicadas screaming].

I realized that those of you living outside of the United States might not know what I'm talking

about. That is the sound of cicadas the dumb, clumsy, noisy insects with transparent wings

and big ol' compound eyes. And, before you say it, yes it's true that there are some

3,000 species of cicada and they live all over the world. But the variety I'm talking

about are periodical cicadas that only live in North America.

Cicadas species fall into two broad groups: annual that can be seen every year, and periodical

that emerge in cycles that last 13 or 17 years. That's not to say a certain species can

only be spotted every 13 or 17 years, because the same species can have multiple broods

that emerge in different years across different geographical regions. There are 15 brood cycles

and the one set to emerge this year is one of the largest: brood X. Billions of these guys will climb

out of their little underground burrows and shriek their little hearts out when it's

warm enough to do so. Before emerging, periodical cicadas spend

all those years underground in the nymph stage of their life cycle, drinking the liquids

from plant roots. How they coordinate coming out all together is anyone's guess. It's

possible changes in the root's fluid clue them in on how much time has passed, or their

bodies tick off freeze-and-thaw cycles. But either way they can reliably count down 13 or 17

years, depending on the species. Why this long is a mystery.

Maybe they're just waiting for a prime time… get it, because 13 and 17 are… prime numbers.

Actually no, the prime interval may help them survive by keeping them from syncing

up with their predators' life cycles. Anyway, once that time has  passed and the soil temperatures hit about 18 degrees

celsius they dig themselves out of the ground like a zombie hoard.

Sure they had long and safe lives underground,

but they're teenagers now. It's time for them to get out there, find a nice mate, settle

down and have hundreds of offspring. You know how it is.

So after they come out en masse and molt out of their

nymph forms to let their new winged adult bodies harden overnight, it's mating time, baby!

To attract a mate, the males have special

ribbed membranes on their abdomens called tymbals. By contracting and relaxing their

tymbals 120 to 480 times a second, the males can sustain a humming noise. Each cicada species

has a unique song that only attracts females of the same species.

Hilariously though, lawnmowers can create sounds at the same frequency as some males,

causing people doing yard work to be swarmed by lady cicadas drawn by what they think is

And you thought having a nice car was a chick magnet.

Males tend to congregate and sing in chorus, chirping away at more than 90 decibels. Not

only does this help the females know where to find a partner, the sound also repels birds.

That's not to say they're safe from predators. Actually, far from it. The clumsy little guys make easy

prey and predators gorge themselves on the surprise feast. But there's just so many

of them that predators can't eat them all, or even really put a dent in the population.

That might actually be their survival strategy, which is called predator satiation. Once the

feast is done, the survivors are free to get buzzy.

Females can lay up to 600 eggs, which they typically deposit in the wood of dozens of

twigs and branches. Four to six weeks after emerging from the ground, the adult cicadas

die off. Shortly after that, their eggs hatch and a new generation of nymphs makes its way

to the ground to start the process all over again.

This whole thing involves some pretty incredible coordination and timing, but even so, some

of brood X emerged early in 2017. One theory points to climate change. Scientists are seeing

broods emerge early more and more often and the changing temperatures appear to be the

only common factor that could explain why their internal clocks are off.

Most of them are still set to emerge this year. If you live outside North America and

this all sounds like a natural wonder you'd like to see, you can visit and see broods

XIII and XIX emerge in 2024. But if you want to see the next wave from brood X, you're

going to have to wait until 2038. Mark your calendar if you plan on doing some yard work

then maybe just stay off the riding lawn mower.

but why would humans intentionally breed and release millions of mosquitoes? Check out

this video to find out more. If you liked this video, let us know in the comments below.

Make sure to subscribe and thanks for watching. I'll see you next time on Seeker.