The money spider (Linyphiidae), Carorita limnaea was given a Great Britain (GB) Rarity Status of ‘Nationally Rare’ and a GB IUCN threat category of ‘Vulnerable’ in the 2017 review of the scarce and threatened spiders (Araneae) of Great Britain (Harvey et al, 2017).
Rationale for IUCN classification (Harvey et al, 2017)
Known from just two sites since 1992 and at one of these from a single specimen. Within this restricted AOO the extent and quality of its Sphagnum bog habitat has suffered decline, but is now apparently improving under conservation management.
UK site discovery years
Wynbunbury Moss: 1962
Fenns / Whixall / Bettisfield / Moss Complex: 1993
In 2017 at it’s only Cheshire site, Wynbunbury Moss NNR, C. limnaea was found widely and in good numbers in quaking bog by Richard Gallon after an 18 year gap between records. The spider was found at all 7 sampling points and a total of 40 females and 4 males were recorded. However, despite an extensive surveys of other floating bogs on the Cheshire Plain during the same year using a vacuum sampler (chiefly in search of Sitticus floricola) (Gallon, 2018), no new sites were discovered.
It’s occurrence at the Whixall Moss complex (Shropshire / Denbighshire) was based on a single specimen from 1993 by Rixom until Autumn 2017 when R. Gallon found 6 adult females in the Bettisfield Moss part of the wetland complex. In 2018, R. Gallon et al, found adults in both Bettisfield (Shropshire part) and Fenns (Denbighshire) mosses. The latter may represent the first Welsh record of the species although older GRs give vague locations that overlap the border. At the time of the above 2017 and 2018 findings, C. limnaea was considered to be more numerous at Wynbunbury Moss (R. Gallon pers. comm. 2020).
A restricted suite of peatlands. The Northern Ireland Priority Species account for C. limnaea lists fen; transition fenland; quaking bog; transition bog; schwingmoor (subsidence raised mire); and kettle-bog with quaking vegetation (habitas.org.uk). The SRS summary page (2020) reads: ‘Occurs on Sphagnum bogs, sometimes in association with Erica tetralix, Eriophorum and Vaccinium oxycoccus‘. At Wynbunbury, the species occurs on quaking bog. On the quaking bog at Bettisfield Moss, the spider has been found in bog-moss hummocks surrounded by open water. This micro-habitat is very humid and is also exposed, receiving maximum heat from sunlight.
Largely unknown. Adult of both sexes are found in June through to October but it’s likely few searches have taken place during Winter or Spring. Immature C. limnaea have not been recorded in the UK, owing to identification difficulties.
Recording / Identification
Like many linyphiids, immature C. limnaea can’t currently be reliably recorded using morphological characters so the adult season must be targeted for species surveys unless DNA barcoding is used. Detection of C. limnaea was formerly reliant on meticulous sieving and sorting of Sphagnum moss by hand. Recently, vacuum samplers have been used very effectively to find C. limnaea at both UK sites and they are particularly suited to recording spiders in bog habitats.
Identification Key: The Spiders of Great Britain and Ireland (Roberts). Originally published in three volumes in 1985-87, it was re-issued in a two-volume ‘compact’ edition in 1993. Still the current work for identifying British spiders that require microscope study. Available to order from the major natural history booksellers.
The two known extant sites have legal protection as designated SSSIs and are managed for wildlife conservation. Fenns, Whixall and Bettisfield Mosses also has a European Union designation as a Special Area of Conservation (SAC).
Wynbunbury Moss – owned and managed by Natural England as a National Nature Reserve (NNR)
Fenns, Whixall and Bettisfield Mosses – owned and managed by Natural England and Natural Resources Wales as a National Nature Reserve (NNR).
The quaking bog area of Wynbunbury NNR clearly supports a large population of C. limnaea (C. Felton & S. Judd 1997; R. Gallon, 2018) and there is no obvious immediate danger to it’s viability at this site. However, Wynbunbury is a small (11.43ha) and isolated reserve, and there is only one discrete area of quaking bog, which makes it more vulnerable to local extinction events. The site has suffered from surrounding agricultural run-off and eutrophic water from an adjacent house in the past but these issues have been addressed (including taking control of some surrounding land) and the ecological recovery is on-going (Natural England, 2014). Much effort in recent years has gone into control of scrub encroachment, which stood as perhaps the greatest threat to the quaking bog invertebrates specialists such as C. limnaea. The fact that both UK sites are designated for their lowland bog habitats and are under government agency ownership and management, whom actively work to protect and improve the condition of the bog communities, goes a long way towards safeguarding the future of this tiny spider in Britain. Regular surveillance of the populations would help to detect any declines.
R. Gallon (2018) Tanyptera Project Sitticus floricola report – contains details of C. limnaea findings during a landscape-scale 2017 survey.
Felton, C. & Judd, S. 1997. Carorita limnaea (Araneae: Linyphiidae) and other Araneae at Wybunbury Moss, Cheshire – a unique refuge for two relict species of spider in Britain. Bull. Br. arachnol. Soc., 10: 298–302.
Harvey, P., Davidson, M., Dawson, I., Fowles, A., Hitchcock, G., Lee, P., Merrett, P., Russell- Smith, A. & Smith, H. 2017. A review of the scarce and threatened spiders (Araneae) of Great Britain: Species Status No. 22. NRW Evidence Report No: 11. Natural Resources Wales, Bangor.
Judd, S. 1996. The status of the Red Data Book 1 money spider Carorita limnaea (Crosby & Bishop) at Wybunbury Moss NNR, Cheshire (SJ697503) – its only known British location. Report for English Nature.