Emergence of mayfly provides feeding bonanza
NO marks for guessing how mayflies got their name.
In days or yore when people didn’t have the benefit of Googling plants and animals to discover their names, mayflies were the flies that became prominent at the end of the month of May. Similarly, the ‘May bush’ (Hawthorn) produced its white flowers during the present month, the ‘May bird’ ( Whimbrel) passed through on migration and the big ‘May bug’ (Cockchafer) alarmed everyone when it accidentally flew into windows making a bang.
Despite their name, mayflies are not confined to May and can emerge from April to November depending on the species. An adult mayfly is a delicate-looking insect. It holds its long wings upright like those of a butterfly rather than folding them flat on its back like those of a bee, wasp or fly. It also has two or three long, thread-like tails projecting from its rear end.
Females lay eggs and like dragonflies they lay them in water. The eggs hatch underwater and the creature that emerges from each egg is known as a nymph. The nymph stays underwater and lives a completely aquatic life lasting one or two years.
The nymph is the main feeding and growing stage of the insect’s life cycle and is long-lived. The adults are very short-lived; their sole purpose in life is to reproduce and to lay more eggs in more waterbodies to perpetuate the species. In fact, there are two adult stages, something that is unique among insects.
To turn into a flying adult, each aquatic nymph climbs up a water plant, emerges from its watery world into the air, reveals its wings as it sheds its underwater coat and takes off to hide in nearby vegetation.
The emerging insects are the non-sexual, sub-imago or ‘dun’ stage that escapes from the water and makes the transition to the air. The dun moults into a breeding ‘spinner’ that ascends to join others on a short-lived nuptial flight. Males die after breeding; females lay eggs into the water before they die too. The emergence is synchronised and the sheer numbers of bodies provide a feeding bonanza for wagtails, trout and ducks.
Anglers capitalise of the annual phenomenon by casting artificial flies attached to hooks into the water to catch a hungry trout when its attention is focused on the feeding frenzy and when it is more likely to snap at anything that resembles protein-rich, fast food.
The Green Drake is one of the commonest of the 33 species of mayfly found in Ireland.