Irish mayflies under threat of extinction

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Upland Summer Mayfly Ameletus inopinatus (Photo: Stuart Crofts)

A new red list has just been realised by National Parks and Wildlife Service, Northern Ireland Environment Agency and the National Biodiversity Data Centre. It assessed the threat of extinction to all 33 species of Irish mayflies. Six species are assessed as under threat of extinction and two species near threatened.

Mayflies , the oldest of the extant insects, are indicators of the general health of our rivers and lakes. They are susceptible to water pollution because their larvae live on river or lake beds typically for one to two years, growing and molting about 20 times before surfacing as short-lived adults. The insects vary from in length as nymphs from less than 10mm for caenid species to 22mm in the case of the Green Drake Mayfly (Ephemera danica). As adults they have bulging eyes, two pairs of translucent, vein-lined wings and two or three filament-like tails.

Mayflies tend to hatch and swarm one or three times a year, from April to as late as November for some species Once hatched and aloft in dancing swarms, the males seize females and mate on the run. The male promptly dies. Each female drops thousands of eggs into the river and then dies, too. Along with stoneflies and caddisflies, mayflies are a very important component of many fish species’ diet.

Dr. Mary Kelly-Quinn, the main author of the list, said “water pollution is the key threat to the species listed. The implementation of the objectives of the Water Framework Directive, however, should bring about improvement in water quality and help stem losses in aquatic biodiversity. In the interim the listed species should be prioritized for regular monitoring”.  Anglers and those who frequent rivers and lakes could help in this effort.

The red list is available online here.