July 2013 - Mayflies

Photo taken by Lindsey Stephens - Bawburgh 27th May 2013

There are 51 species of mayfly to be found throughout the UK. They are beautiful and delicate insects and are to be seen flying in areas near and just above the surface of the river on sunny days. An alternative name for these insects is 'dayfly' because the adults of some species of mayfly, including the one shown, only live as long as a day, sometimes only a few hours. Their current name is derived from the mayflower, alternatively known as the hawthorn, which blooms at the same time as the adults emerge from their water habitats. Although their name suggests that they only emerge as adults in May, this is untrue, and adults can emerge from May to September. Adult mayflies do not feed and in fact they do not have mouths, their short life being taken up solely looking for a mate. Once mated the males die, while the females lay their eggs in rivers, ponds and lakes, then they too die. Nymphs hatch from these eggs and live for two years in their water habitat, feeding on aquatic plants and algae, before emerging from their larval cases as adult mayflies on bright sunny days.

Mayflies can be identified by their three long tail filaments (some only have two), and short antennae. Their wings are held vertically over their backs when resting. They have smaller hind wings than forewings, as seen in the above photo.

These insects are sensitive to pollution and their presence is a good indicator of the quality of our water systems. However, the overall trend for UK populations of mayflies, as for many other river flies including caddis flies and stone flies, is one of decline which is of great concern. Both larvae and adults are a vital source of food for many fresh water creatures including fish, and many species of insect eating birds. A significant decrease in the insects will affect the whole food chain. 

Fossils of these insects dating back 300 million years can be found embedded in amber.




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