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Ecdyonurus insignis (Large green dun)

Ecdyonurus insignis is a highly localised species with records from a small number of watercourses in southern England and Scotland.  This apparent rarity may be due to under-recording.  Nymphs of this species are typically found in riffle areas of rivers and streams.  They are usually found clinging to submerged plants and stones, although they may swim if disturbed.  E. insignis 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 October.

 


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Males swarm during the afternoon and often well into dusk.  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 3500 eggs is finished and the spent female falls on to the surface.