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Electrogena lateralis (Dusky yellowstreak)

Electrogena lateralis is a common, though localised species in Scotland, Wales and the North and South West of England.  Nymphs of this species are typically found in riffle areas of rivers and streams, although they can also occasionally be found on the wave-lashed shores of standing waters.  The nymphs are usually found clinging to submerged plants and stones, although they may swim if disturbed.  E. lateralis feeds either by scraping periphyton from the substrate or by gathering fine particulate organic detritus from the sediment.  There is one generation a year, which usually overwinters as nymphs and emerges between May and September.

 


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Whilst this species can emerge at the surface of the water, it is unusual in that it can also emerge under water on the surface of a submerged stone.  This allows the adult fly to leave the water surface immediately on reaching the surface thus minimising the possibility of capture by fish or surface skimming birds such as swallows and sand martins.  Once mated, the female flies upstream and descends to the surface of the water to release a few eggs by dipping the tip of her abdomen on to the surface at intervals, or by actually settling on the surface for short periods.  After several visits to the water the egg supply of up to 2500 eggs is finished and the spent female falls on to the surface.