Every 17 years, members of a group of periodical cicadas (known as Brood X) start to emerge from their underground hiding-places, shedding their skins on trees and turning into adults.
Billions and billions of these cicadas from 15 US states start to come to the surface when the soil above them hits a temperature of 17.7ºC.
Within a matter of weeks, these cicadas will emerge, grow into adults, breed, lay eggs and die, and won't be seen again for another 17 years.
Colette Lord, 20, an ecology and evolution student at the University of Maryland, measures the soil temperature in a wooded area on campus on 3 May 2021 in College Park, Maryland, USA. The soil measured 14.4 degrees celsius, slightly cooler than necessary for the periodical cicadas from Brood X to emerge. Lord is part of a group of 15 students who are measuring and monitoring the area for the rise of billions of the airborne insects that have been eating and growing under ground for 17 years. Photo by Chip Somodevilla/Getty Images
Emergence
A periodical cicada begins to moult from its nymph state on 10 May 2021 in Takoma Park, Maryland, USA. Photo by Chip Somodevilla/Getty Images
Shed this skin
An adult cicada sheds its nymphal skin on the bark on an oak tree, on 4 May 2021 at the University of Maryland campus in College Park, USA.Photo by Carolyn Kaster/AP/Shutterstock
An empty shell
The empty shell of a periodical cicada nymph clings to a tree after the adult insect moulted on 10 May 2021 in Takoma Park, Maryland, USA. Photo by Chip Somodevilla/Getty Images
Ready to fly
A Brood X 17-year cicada photographed in Fairfax, Virginia, USA, on 10 May 2021.Photo by Carol Guzy/ZUMA Wire/Shutterstock
Inside the empty shell
The empty shell of a periodical cicada nymph clings to a tree after the adult insect moulted on 10 May 2021 in Takoma Park, Maryland, USA. Photo by Chip Somodevilla/Getty Images
Clinging on
The empty shell of a periodical cicada nymph clings to a tree after the adult insect moulted on 10 May 2021 in Takoma Park, Maryland, USA. Photo by Chip Somodevilla/Getty Images
Preparing for the wave
In anticipation of the emergence of billions of periodical cicadas, this young tree is wrapped in netting to prevent the insects from depositing eggs in the small branches on 10 May 2021 in Takoma Park, Maryland, USA. Photo by Chip Somodevilla/Getty Images
Branching Out
A periodical cicada nymph clings to a tree branch on 11 May 2021 in Greenbelt, Maryland, USA. Some are waiting for their arrival with trepidation, others are curious what they might taste like. Americans are swapping tips on how best to weather the storm when billions of cicadas soon emerge. Photo by Jim Watson/AFP/Getty Images
Spot the cicada
A woman looks at a Brood X cicada which has emerged from the ground along First Street on Vinegar Hill in Bloomington, Indiana, USA, 14 May 2021.Photo by Jeremy Hogan/SOPA Images/LightRocket/Getty Images
Coming out of the ground
Brood X cicadas emerge from the ground along First Street on Vinegar Hill in Bloomington, Indiana, USA, 15 May 2021Photo by Jeremy Hogan/SOPA Images/LightRocket/Getty Images
More empty shells
A periodical cicada is seen in the middle of empty cicadas shells, displayed by a child on the ground, on 16 May 2021 in Arlington, Virginia, USA.Before invading parks and people's gardens, the insects have already conquered the airwaves, social media and newspapers, especially in parts of the eastern, central and southern United States where "Brood X" is due to emerge. Photo by Olivier Douliery/AFP/Getty Images
Visiting the Capitol
The empty shell of a cicada clings to the side of a tree at the US Capitol in Washington DC, USA, on Sunday morning, 16 May 2021. Photo by Bill Clark/CQ-Roll Call, Inc/Getty Images
James Cutmore is the picture editor of BBC Science Focus Magazine. He has worked on the magazine and website for over a decade, telling compelling science stories through the use of striking imagery. He holds a degree in Fine Art, and has been nominated for the British Society of Magazine Editors Talent Awards, being highly commended in 2020. His main areas of interest include photography that highlights positive technology and the natural world. For many years he was a judge for the Wellcome Trust's image competition, as well as judging for the Royal Photographic Society.
TAKOMA PARK, MD - MAY 10: The empty shell of a periodical cicada nymph clings to a tree after the adult insect molted on May 10, 2021 in Takoma Park, Maryland. Once soil temperatures reach about 64°F, billions and billions of these periodical cicadas -- members of Brood X -- will emerge in fifteen states and the District of Columbia after living underground for 17 years. The cicadas will emerge, molt, mate, lay eggs and die within a matter of weeks. (Photo by Chip Somodevilla/Getty Images)
