Wildlife Photographer of the Year: dancing on the Danube
Twirling mayflies above the Danube gave Hungarian photographer Imre Potyó a chance to capture a fleeting but spectacular moment.
Tiny mayflies have made their home on Hungary's rivers, where they put on a remarkable annual show.
These insects are an endangered species. The adults have a lifespan of just a few hours, and the most important moment of their short lives is the one in which they reproduce.
When the time is right, the mayflies swarm above the rivers in huge clouds, frantically pairing up to mate and lay eggs, before collapsing and dying in the dark water.
It's an evening event that fills the air with whirring wings.
For the last few years, photographer and environmental researcher Imre Potyó has been there to capture the chaos on camera. Two of his images are on display in the Wildlife Photographer of the Year exhibition.
He says, 'I'm addicted to unique and unusual atmospheres, especially during the night.
'I first photographed the mayflies' swarming activity in the summer of 2013, and the next year I was determined to shoot them in front of the starlit sky.
'They only swarm for about an hour and a half, so I didn't have long to put that plan into action.'
The swarming of the mayflies usually starts at the end of July or beginning of August. It takes place on the Danube River and its tributaries, such as the Rába, and can be repeated for several evenings.
The life of mayflies is short and their swarming dates are unpredictable. They start to fly after sunset and do not leave the water's surface.
To begin, both males and females hover above the water, where they mate. Afterwards, the females fly higher before laying eggs on the water.
Imre captured a group of females laying eggs in the above image, Light fandango.
He says, 'The picture shows the egg laying very artfully, with a long exposure and lots of light. It was taken on a dark bank of the Danube River in Tahitótfalu, Hungary.
'My equipment was totally covered by the huge mass of buzzing mayflies. They were all around me - it was a fantastic feeling. Their wings rustle and whir very loudly at the peak of the swarm.
'I took hundreds of pictures, but the composition was correct in only one or two.'
Imre took a second image on a tributary of the Danube, the Rába river. It is also on show in the Wildlife Photographer of the Year exhibition, alongside other images from photographers from around the world.
The 34-year-old got the shot, Swarming under the stars, in August 2015.
He says, 'During that evening's swarming, the weather conditions were so clear near the river, I could shoot the mayflies with the bright stars in the background, as I imagined it.
'I illuminated the insects with a continuous bright flashlight for the picture.'
Imre has done extensive work at the MTA Centre for Ecological Research in Hungary, where researchers study the country's biodiversity.
As an assistant research fellow, he worked with other experts to study the behaviour of the mayflies. He hopes his images will draw attention to the endangered species.
He says, 'These images are very precious to me because I can use them to draw attention to spectacular endangered water insects.
'They are very important from the perspective of popular science. Photographs that get attention can positively impact the thinking of a huge number of people.'