Nature Studies: Mayflies offer gripping scenes of mass birth, mass sex and violent death

You don't need to go on safari in Africa to encounter a gripping wildlife spectacle. In England there's one coming to an end just about now


Wildlife spectacle is something to encounter abroad, we tend to think, perhaps reaching its peak in Africa with the great annual migrations of wildebeest and zebra from the Serengeti to the Masai Mara, on the Kenya-Tanzania border; as many safari tourists witness, the thundering thousands are preyed upon during their journeys by lions and hyenas, and even crocodiles as they cross the Mara river, in scenes of unforgettable drama.

Nothing like that in Britain, you might think, certainly not in the cosy and unchallenging countryside of southern England; but you’d be wrong. There is a gripping English wildlife spectacle, coming to an end just about now, which involves thousands of individual creatures in scenes of mass birth, mass sex and violent death; the only difference is one of scale.

For these creatures are mayflies, the graceful, butterfly-sized upwing flies of our purer rivers, especially the southern chalk streams like the Hampshire Test and the Berkshire Kennet. Every year, they hatch in enormous numbers, mate, lay their eggs in their river and then fall exhausted to the surface where they are pounced on with unremitting violence by trout. It’s a spectacle and a half, and I’ve just been watching it on the Dorset Frome, Thomas Hardy’s river which flows through Dorchester (and is pronounced “Froom”, as opposed to the three other, quite separate River Fromes in Somerset and Gloucestershire, which are pronounced “Froam”).

It happens right at the end of the mayfly’s two-year life cycle, all but the last day of which is spent underwater as a nymph, a wingless larva; the part we witness, the elegant life in the air, is over so quickly, so ephemeral, that the mayfly insect order is known as the ephemeroptera. 

It starts when the nymph swims to the surface and changes into an adult mayfly, before seeking shelter in bankside vegetation. This is because, uniquely among insects, mayflies need to moult again after emerging as adults, before they are sexually mature.

When I arrived at the river, they were everywhere in the buttercup-speckled water meadows, thousands of them newly hatched and clinging to the grass stems, waiting for the world to warm up. And when it did, and they had shed another skin, the males began their courtship dance.

They bounce. That’s the only word for it. They fly up vertically, to 12 or 15 feet perhaps, then parachute back down to about four feet from the ground; but the return back up again is so abrupt that they appear to have landed on an invisible trampoline. Watching a mass swarm of them bouncing in the air is like watching kids on a bouncy castle, and it is a peculiar feeling to ascribe a human exclamation to an insect, the only time I have ever done it: I couldn’t stop imagining them going “wheee!”.

It’s visible from a distance, and the much larger females are attracted, fly in, and are grabbed and inseminated; then, while the males fly off to die in the grass, the females head back to the water to lay their eggs – they’re now known as spinners, from their spinning, egg-laying flight – and eventually collapse, spent and helpless in the surface film.

The phenomenon is known as a fall of spinners, and when it happens on any sort of scale, it brings the river magically alive. The trout go mad; even the big ones will snatch these lumps of protein in slashing, lacerating surges, and every pool holds rising fish. I watched from the bankside of the Frome as the light began to fade and the mayfly spinners floated down to the surface and the trout rose up to take them. Splash after splash. Ker-ploop. Pe-loosh. A watercourse vibrating with life and death.

It may not have been crocodiles grabbing zebras, but I tell you, I was enthralled.

Twitter: @mjpmccarthy

election 2015The 10 best quotes of the campaign
A caravan being used as a polling station in Ford near Salisbury, during the 2010 election
election 2015The Independent's guide to get you through polling day
David Blunkett joins the Labour candidate for Redcar Anna Turley on a campaigning visit last month
voicesWhat I learnt from my years in government, by the former Home Secretary David Blunkett
Have you tried new the Independent Digital Edition apps?
  • Get to the point
Latest stories from i100
Have you tried new the Independent Digital Edition apps?
iJobs Job Widget
iJobs General

Ashdown Group: Marketing Manager (B2B) - Romford - £40,000 + car

£35000 - £40000 per annum + car and benefits: Ashdown Group: Marketing Manager...

Ashdown Group: Helpdesk Analyst - Devon - £20,000

£18000 - £20000 per annum: Ashdown Group: Helpdesk Analyst - Devon - £20,000 ...

Ashdown Group: Data Scientist - London - £50,000 + bonus

£35000 - £50000 per annum + generous bonus: Ashdown Group: Business Analytics ...

Ashdown Group: IT Project Coordinator (Software Development) - Kingston

£45000 - £50000 per annum: Ashdown Group: IT Project Coordinator (Software Dev...

Day In a Page

General Election 2015: ‘We will not sit down with Nicola Sturgeon’, says Ed Balls

'We will not sit down with Nicola Sturgeon'

In an exclusive interview, Ed Balls says he won't negotiate his first Budget with SNP MPs - even if Labour need their votes to secure its passage
VE Day 70th anniversary: How ordinary Britons celebrated the end of war in Europe

How ordinary Britons celebrated VE Day

Our perception of VE Day usually involves crowds of giddy Britons casting off the shackles of war with gay abandon. The truth was more nuanced
They came in with William Caxton's printing press, but typefaces still matter in the digital age

Typefaces still matter in the digital age

A new typeface once took years to create, now thousands are available at the click of a drop-down menu. So why do most of us still rely on the old classics, asks Meg Carter?
Discovery of 'missing link' between the two main life-forms on Earth could explain evolution of animals, say scientists

'Missing link' between Earth's two life-forms found

New microbial species tells us something about our dark past, say scientists
The Pan Am Experience is a 'flight' back to the 1970s that never takes off - at least, not literally

Pan Am Experience: A 'flight' back to the 70s

Tim Walker checks in and checks out a four-hour journey with a difference
Humans aren't alone in indulging in politics - it's everywhere in the animal world

Humans aren't alone in indulging in politics

Voting, mutual back-scratching, coups and charismatic leaders - it's everywhere in the animal world
Crisp sales are in decline - but this tasty trivia might tempt back the turncoats

Crisp sales are in decline

As a nation we're filling up on popcorn and pitta chips and forsaking their potato-based predecessors
Ronald McDonald the muse? Why Banksy, Ron English and Keith Coventry are lovin' Maccy D's

Ronald McDonald the muse

A new wave of artists is taking inspiration from the fast food chain
13 best picnic blankets

13 best picnic blankets

Dine al fresco without the grass stains and damp bottoms with something from our pick of picnic rugs
Barcelona 3 Bayern Munich 0 player ratings: Lionel Messi scores twice - but does he score highest in our ratings?

Barcelona vs Bayern Munich player ratings

Lionel Messi scores twice - but does he score highest in our ratings?
Martin Guptill: Explosive New Zealand batsman who sets the range for Kiwis' big guns

Explosive batsman who sets the range for Kiwis' big guns

Martin Guptill has smashed early runs for Derbyshire and tells Richard Edwards to expect more from the 'freakish' Brendon McCullum and his buoyant team during their tour of England
General Election 2015: Ed Miliband's unlikely journey from hapless geek to heart-throb

Miliband's unlikely journey from hapless geek to heart-throb

He was meant to be Labour's biggest handicap - but has become almost an asset
General Election 2015: A guide to the smaller parties, from the the National Health Action Party to the Church of the Militant Elvis Party

On the margins

From Militant Elvis to Women's Equality: a guide to the underdogs standing in the election
Amr Darrag: Ex-Muslim Brotherhood minister in exile still believes Egypt's military regime can be replaced with 'moderate' Islamic rule

'This is the battle of young Egypt for the future of our country'

Ex-Muslim Brotherhood minister Amr Darrag still believes the opposition can rid Egypt of its military regime and replace it with 'moderate' Islamic rule, he tells Robert Fisk
Why patients must rely less on doctors: Improving our own health is the 'blockbuster drug of the century'

Why patients must rely less on doctors

Improving our own health is the 'blockbuster drug of the century'