Thousands of mayflies take flight over the pond in the heat of May. For a few days, a few hours. Without eating, they are present for a moment, to ensure the perenniality of the species.
The mayfly
2 to 3 cm long, it can be recognized by its arched body, its slender abdomen prolonged by thin rings, its vertical wings, its reduced antennae. The mayfly belongs to the large group of Ephemeroptera, along with hundreds of cousins difficult to differentiate from each other as they are so similar.
All over the world they are found in thousands of species, under all latitudes, except the coldest. Except also Iceland and some Pacific islands. Their life is divided between the aquatic world, for their larvae, and the air, for the adults.
An ephemeral life
The adult mayflies fly away in spring, for a few hours, 2 to 3 days at the most. Their so short life is devoted only to the reproduction, as soon as emerged the males fertilize the females, the long front legs allowing a firm catch. Immediately, the mayflies will lay eggs.
For certain species, the eggs will be released in full flight, others will pose them on water or just on the surface, others still will fix them to immersed substrates.
A single female will emit 500 to 6000 eggs. Then will disappear, without having even sought to nourish itself. Its digestive organs and mouth parts, regressed, do not play any more any role.
Long life to the young
The eggs of Ephemera will give birth to small larvae with the entirely aquatic life. They breathe with external gills, 2 rows of 7 arranged along the abdomen. Their shape, aspect, differ according to the species, and allow determinations with a magnifying glass. Just like the antennas, more or less short. The larvae are remarkable for their long and fine cerci, 2 to 3, extending their abdomen. To feed they have crushing parts, and are for the majority detritivores.
But some species have adapted to other food regimes, scraping the substrate, filtering, sometimes predatory. They need about twenty moults, during several months, to reach a pre-adult stage, the subimago, rapidly transforming into a formed adult.
From mountain streams to marshes
Mayflies are found throughout the world in a wide variety of species and habitats. From mountain streams to calm rivers, from ponds to marshes, all wetlands welcome them. The larvae can be burrowing, crawling, swimming... They disperse according to the currents, carried in the plumage of the birds. Adapted to many environments, extremely prolific, they play an essential role in aquatic ecosystems. Bats, birds, amphibians, fish and insects all take advantage of this abundant food source. Called "manna", for the enormous biomass thus provided.
Nowadays, we hardly see the spectacular spring swarms of mayflies anymore. Victims of pesticides, of the loss of their habitats, of their attraction for artificial lights, they are in clear regression. What if the manna of the wetlands disappeared?
