91热爆

Cicadas: Brood X to emerge after being underground for 17 years

A close up of a 17-year periodical cicada.Image source, Universal Images Group via Getty Images
Image caption,

A 17-year periodical cicada up close

If you think lockdown has been long, then imagine being underground for 17 years!

That's what these insects - called periodical cicadas - have been doing in America and now they're ready to show the world what they've got.

They are due to emerge from the ground in 18 US states, including Washington DC, Michigan and West Virginia, later this month.

As many as 1.5 million of the insects can come out of the ground per acre of land, meaning that tens of billions in total will emerge.

The last time the cicadas emerged in many of the US regions was in 2003 and 2004, though some areas saw an emergence in 2013.

The species make up 15 separate "broods", with Brood X (meaning ten) emerging this year as part of their 17-year cycle.

They are some of the longest-living insects in the world, but spend almost their entire lives underground and feed on tree roots for periods of 13 to 17 years.

When they are ready to come to the surface, they build mud tubes - called a cicada hut - in the soil and crawl out to find a place to moult into their winged adult form.

But don't worry, even though there's billions of them they aren't harmful to humans and can be a good food source for animals and birds.

Image source, JIM LO SCALZO

And don't confuse cicadas with locusts - plagues of locusts can devastate crops and cause many problems in some parts of the world.

However, it sucks to be a tree when the cicadas are around because, even though they only live as adults for two to four weeks, they feed on young trees and vines, and can cause significant damage in the process.

One of the main reasons why they come out of the ground is to mate. The male cicadas are really loud and attract the females by vibrating - which creates a sharp buzz singing noise.

Scientists have measured the noise and think it's a similar level to a motorcycle!

And, just in case you were wondering, humans can eat cicadas if they want to because they are edible and are a really good source of protein.

Why the insects emerge on these specific periods remains unclear, though some researchers think it could help them avoid predators.