Riverflies - Species of Principle Importance

Riverflies are at the heart of freshwater ecosystems and are a vital link in the aquatic food chain as a food source for fish and birds. There are eight rare and threatened riverflies which have been designated as conservation priorities by the UK Government and are listed as species of Principal Importance.

The eight riverflies designated as conservation priorities species of principal importance by the UK Government are:

Northern February red (Brachyptera putata): a stonefly that occurs only in Britain. It is found mainly in Scottish upland streams.

Rare medium stonefly (Isogenus nubecula): only known to occur in the Welsh River Dee and may now be extinct.

Scarce grey flag (Hydropsyche bulgaromanorum): a large caddisfly only known from stony areas on the River Arun in Sussex.

Scarce brown sedge (Ironoquia dubia): a caddisfly only known from three southern English sites, and there are no recent records for this species.

Small grey sedge (Glossosoma intermedium) a caddisfly that has been found in only four Lake District streams; however there are no recent records for this species.

Window-winged sedge (Hagenella clathrata) an orange mottled caddisfly that lives in pools on bogs and heathland at about ten sites in the UK.

Southern iron blue (Baetis niger): a widespread mayfly species whose abundance appears to have declined in some areas by as much as 80% in recent decades.

Yellow mayfly (Potamanthus luteus): an attractive, bright yellow mayfly that is found mainly on the River Wye in the Welsh borders.