brief encounter

With only one day to live and breed, adult mayflies have no time to lose, writes

Most flies live for a week or longer, given the chance, and they generally feed as adults, which we know from trying to eat lunch outside! Adult mayflies – which are not true flies – usually live for only one day. If you’ve seen trout-fishing flies made from feathers and fine thread, you know the insect I’m talking about, and if you have a large pond in a garden in the mountains, you’re likely to have mayflies in your yard.

Like many insects, the juvenile is very different to the adult. The nymph of the mayfly lives in water and breathes through gills during a phase that lasts for a year or longer. It feeds on algae and detritus on the bottom of the pond, and sheds its skin several times.

When it climbs out of the water, it sheds its skin again to become a mayfly. In the process, it loses most traces of a mouth and digestive tract, and cannot feed. With no time to waste, it flies off to mate, finds a suitable watery place to lay its eggs, then dies. Often, mayflies seem to not even lay their eggs, but to drop onto the water’s surface and burst, showering eggs into the flow.

Most flying insects get their wings when they shed their skin for the last time to become an adult. This happens in the last stage of life because wings are very thin – it would be difficult to shed the outer layer to form a new set of wings underneath. But the mayfly, during its one day of adult life, takes the complex step of shedding its skin again, wings and all, to become a more refined version of its first winged stage. This is partly why there are so many different trout-fishing flies: the fly maker mimics each species in both stages (dull-coloured at first; paler or patterned later) to entice trout to bite.

So when you think life is far too rushed, and the days too short, spare a thought for the mayfly, which has to pack its entire adult life into one day!