Summary details for Carorita limnaea (Crosby & Bishop, 1927)

Distribution

In Britain, the species is recorded only from Wybunbury Moss, Cheshire, where it was first found in 1962 and Whixall Moss, Shropshire where it was discovered in 1993. The spider fauna of the Cheshire Mosses is well-studied, but Wybunbury Moss is the only one at which this species has been recorded. It has been abundant at the site, but a brief search in 1988 failed to find it and it was only in 1993 that it was recorded again, when one male and twelve females were detected by meticulous sieving and sorting of wet Sphagnum moss on floating bog. At Whixall Moss, only a single male has been found despite the intensive and extensive nature of an English Nature survey. It is also known from Ireland, Sweden, Germany, Finland, the Czech Republic and Poland.

Habitat and ecology

It occurs in Sphagnum bog, sometimes in association with Erica tetralix, Eriophorum and Vaccinium oxycoccus. Both sexes are found in June and July.

Status

Known from just two sites since 1992 and at one of these from a single specimen. Within this restricted area of occupancy the extent and quality of the habitat has suffered decline, but is now apparently improving.

Threats

Wybunbury Moss suffered severe pollution from septic tank overflow and road drainage for many years up to 1986. This nutrient enrichment has had a marked effect on the vegetation and is causing the deep peat to degrade. Much of the former Sphagnum lawn has developed into fen. Eutrophication from agricultural run-off still threatens further damage. Further substantial areas of the nutrient-poor raft have developed into pine and birch woodland, aided by previous drainage attempts.

Management and conservation

In 1986 major sources of eutrophic water at Wybunbury Moss were intercepted and diverted away from the reserve. As a result peat degradation and fen encroachment appear to be receding. Removal of invading trees also commenced in 1986 and is continuing with encouraging results. Text based on Dawson, I.K., Harvey, P.R., Merrett, P. & Russell-Smith, A.R. (in prep.).