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Leptophlebia marginata (Sepia dun)

Leptophlebia marginata is a fairly common species that has been found throughout the British Isles, including Ireland.  It is particularly tolerant of the effects of acidification and has been found in waters with pH values of between 4 and 5.  Nymphs of this species can be found in the pools and margins of slow flowing streams and in ponds and lakes where they climb upon the surface of leaves of aquatic plants or crawl in the surface layers of fine sediments, especially mud.  The nymphs are poor swimmers but are adapted for moving amongst dense stands of plants, especially on the surface of the stems.  They feed by gathering fine particulate organic detritus from the sediment.  There is one generation a year, which usually overwinters as nymphs and emerges between April and June.

 


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Nymphs are seldom found in the shallower margins of lakes in any quantity until early April.  As the period of peak emergence approaches, many of the nymphs move into very shallow water.  Emergence of the adults takes place during daylight hours at the surface of the water or more typically, partially or entirely out of the water on a stick, stone or plant stem.  The males of this species can be found swarming throughout the day. 

 

Once mated, the female flies to 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 her supply of around 1200 eggs is finished and the spent female falls on to the surface.