Short and sweet - Mayflies

Andy Fry

Wild Call Officer

There’s a certain irony about one of the oldest animal groups living the shortest adult life in the animal kingdom. Mayflies, thought to be among or descended from the first creatures to take to the skies, have a unique life cycle that has likely remained unchanged for 300 million years.

These ancient insects are still thriving, found in most ponds and waterways in the south of England. Their larvae sit the bottom of ponds and rivers, feeding on algae and plant matter for anywhere between two weeks and two years. A mayfly larva can moult up to fifty times during this period.

When the time comes, they rise to the surface in large numbers and shed their larval skin, on which they rest for a time to dry their wings. While they dry off, they are vulnerable to a whole host of animals eager to make the most of this veritable buffet.

Unlike other insects, this winged form (known as a dun) is not their final form, and does not last long. Shortly after emerging, a mayfly will metamorphose a second time to reveal a brightly coloured adult, also known as a spinner. Adult mayflies lack functional mouthparts and are unable to feed, instead dedicating the rest of their energy reserves to the sole purpose of breeding.

The males often gather in large swarms, each performing their own aerial performance to attract a female. Once paired, they mate on the wing, after which the female will deposit up to 3000 eggs into the water, beginning the cycle again.

Their energy spent, neither male nor female live long after breeding. The longest-lived individuals will last two or three days, with many dying within the first twenty-four hours of emerging.

This ancient ritual may seem odd, but it has proven extremely successful with mayflies still found on six continents, surviving three mass extinctions, relatively unperturbed.