Caenis horaria

This small mayfly is very similar to other members of the family and detailed examination is necessary to reach a safe identification.

May be found near to pools, rivers, streams, lakes and canals.

May to September. The males of this species can be found swarming at dusk and probably during the night.

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. 

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. 

Status in Leicestershire and Rutland not known.