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Caenis horaria (Anglers' curse)

Caenis horaria has a widespread, though localised distribution.  The majority of records for this species are from the South East of England, however there are records from as far north as Sutherland.  Nymphs of this species live in the pools and margins of rivers and streams or in lakes and canals, where they burrow into, and live on mud and silt on the bed of the watercourse.  The nymphs are poor swimmers but are adapted for moving amongst mud and silt where they feed by collecting or gathering fine particulate organic detritus from the sediment. 

 

There is typically one generation a year, which overwinters as nymphs, although some workers have suggested that there may be a further summer generation.  Adults have been recorded between May and September.

 


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Emergence of the adults typically takes place partially or entirely out of the water on a stick, stone or plant stem at dusk.  The males of this species can be found swarming at dusk and probably during the night.