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Cloeon simile (Lake olive)

Cloeon simile is a common and widespread species that is found throughout the British Isles.  It is thought that this species is the least common of the British Cloeon spp.  Nymphs of this species live in pools and margins of rivers and streams or in deeper water in larger lakes.  The nymphs swim in short, darting bursts amongst the substrate, or climb amongst the vegetation.  They feed by scraping algae from submerged stones and other structures, or by gathering or collecting fine particulate organic detritus from the sediment.

 

There are usually two generations a year, one of which overwinters as nymphs and emerges in the spring.  This species has a particularly long flight period with adults generally seen between March and November.

 


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Emergence of the adults typically takes place at the surface during daylight hours, with the males of this species swarming during the morning and afternoon.  Once mated, the female descends to the surface of the water and releases a few eggs by dipping the tip of her abdomen onto the water surface at intervals, or by actually settling on the surface for short periods.  After several visits to the water her supply of up to 3500 eggs is finished and the spent female falls on to the surface.