Magical creatures
AN APPRECIATION OF MAYFLIES
The dinosaur lands on my jacket. I stay still, allowing it some time to bathe its gossamer wings in the late spring sunshine. When it takes to the sky once again, only a few minutes have passed. To me, a brief but pleasant encounter. But the mayfly has just shared with me a significant spell of its adult life. Mayflies have been around for more than 300 million years. They’ve survived a constantly changing environment and seen many other species lost, a feat generally put down to their simple lifecycle. It’s often stated that mayflies only live for a day, but of the 51 species in the UK, adult lifespans actually range from a few hours to a couple of weeks. The adult mayfly has one focus: reproduction. Their precious time will be spent courting, mating and laying eggs. But while their adult life is brief, mayfly larvae, known as nymphs, can live for up to two years.
Nymphs hatch underwater, on a riverbed, and different species will either swim, crawl, or burrow. Crawling nymphs use their strong, clawed front legs to grip on to rocks to prevent them from being washed downstream. Those that swim embrace the fast-flowing water, using it to propel them around. Burrowing nymphs push their way beneath the mud, creating little tunnels to shelter inside. The nymphs’ presence can tell us a lot about a river.
They’re sensitive to water pollution and their presence, or lack thereof, can reveal a lot about a waterway’s health.
The nymphs feed on algae and plants, before emerging on the surface. Despite the name ‘mayfly’, the adults leave the river any time between April and September, selecting warm days when the sun can help dry their wings. Before they reach their fully grown adult form, they uniquely have an interim stage. Nymphs moult as they outgrow their exoskeletons underwater, but after emerging with wings from the water, they moult again casting off their first, dull skin and revealing an iridescent body. We don’t know why they do this; it may be to enable them to further mature, but the process makes them highly vulnerable to becoming dinner for a passing fish, amphibian, or bird.
Once their wings are dry, they take flight again, often en masse, over the water’s surface to dance in billowing clouds, their wings catching the light as they drift up and down, rhythmically floating over the glistening water. Males fly with outstretched front limbs, waiting to bump into females who they will then grab and mate with. Copulation happens in the air and once over, the male’s life is complete, so he falls to the bank, spent. Females will lower themselves to the river, laying their eggs into the water before they also expire, much to the delight of the waiting salmon or trout.
By September, the rivers are quiet again. No more mayflies will emerge until the following year. But beneath the rippling surface, the nymphs are hatching, and a new generation begins.