Carorita limnaea – a spider
Carorita limnaea (Crosby & Bishop, 1927)
Family: Linyphiidae
Carorita limnaea (Crosby & Bishop, 1927) is a minute spider whose rarity across Europe is related to the decline of its favoured environment: a restricted suite of peat and fen type habitats. It preferentially lives amongst vegetation in the wet areas of these habitats.
In brief
- In Northern Ireland it occurs at only two sites, Loughaveely ASSI and Drumlougher Lough ASSI in Co Armagh
- Its preferred habitats are Peatlands: especially fen; transition fenland; quaking bog; transition bog; schwingmoor (subsidence raised mire); kettle-bog with quaking vegetation
- The two Northern Irish sites are mosaic mires situated in basins or hollows. Between them they contain fen habitat with floating fen vegetation, Sphagnum lawn, transition fen and other sub-habitats
- Adult females have been found in Britain from May to the first week of September, males from May to end of August (Fulton & Judd, 1997)
- It is a priority species because it has been deemed rare, as have its favoured habitats, across the UK
- The principal potential threats are: drainage of water from the sites; eutrophication due to water run-off/pollution from adjacent managed areas
Species description
A minute spider 1.1-1.3mm long. Cephalothorax a dusky yellowish-brown with darker lines radiating from the fovea to the margins; abdomen a dark greenish grey. Roberts (1987) suggests it is similar to Maro minutus O.P.-Cambridge, 1906 (see illustration in Roberts, 1985, plate 219).
Life cycle
Little is known. Males are most abundant in June and July so it is likely mating occurs at this time.
Similar species
Males are more easily distinguished from their close congener Carorita paludosa Duffey, 1971, than females. This species can also occur in fen and mire habitats. You should examine very carefully any very small and relatively pale specimens that can occur in similar or related habitats e.g. Maro minutus O.P.-Cambridge, 1906 and Jacksonella falconeri (Jackson, 1908).
How to see this species
It is known only from Loughaveely and Drumlougher Lough in Co Armagh. The species can be caught in pitfall traps or by hand-sifting litter and moss vegetation from wet areas. Hand-collecting can be less time-consuming and more productive of specimens than using pitfalls or a Tullgren funnel. The precise micro-habitat requirements of the species are not understood.
Current status
Known from two sites in Northern Ireland. A single male specimen was collected at each site.
It must be considered rare in Ireland with potentially >50% of the Irish population occurring in Northern Ireland.
Why is this species a priority in Northern Ireland?
UK priority species
Threats/Causes of decline
- Eutrophication of water
- Drainage
Conservation of this species
Current action
Both sites at which C. limnaea occurs are ASSIs and as such any actions that may be detrimental to the habitat and associated species should not occur. There is no current Northern Ireland Species Action Plan.
Proposed objectives/actions
While there is no current Action Plan clearly the two Northern Irish sites should be monitored to ensure no actions take place that may prove detrimental to either the water quality or the nature of the local vegetation, especially the ‘floating’ vegetation. This should assist the spider’s long term survival.
What you can do
Because this species is so small and restricted in habitat choice the chances of meeting it have to be considered slim. In case you feel you may have a specimen of C. limnaea the following may be contacted to provide confirmation: Myles Nolan mylesnolan@hotmail.com.
Further information
UK information
UK Priority Habitats and Species
National Biodiversity Network Gateway
British Arachnological Society
Literature
Bratton, J.H. (ed) (1991). British Red Data Books: 3. Invertebrates other than insects. Peterborough: Joint Nature Conservation Committee.
Crosby, C. R. & Bishop, S. C. (1927). New species of Erigoneae and Theridiidae. Journal of the New York entomological Society 35: 147-154.
Dawson, I., Harvey, P. and Russell-Smith, T. (2008). A National Status Review – the draft results. Newsletter of the Spider Recording Scheme 61 In: Newsletter of the British Arachnological Society 112: 18-24.
Duffey, E. & Merrett, P. (1963). Carorita limnaea (Crosby & Bishop), a linyphiid spider new to Britain, from Wybunbury Moss, Cheshire. Annals and Magazine of natural History 13: 573-575.
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. Bulletin of the British arachnological Society 10: 298-302.
Helsdingen, P.J. van, (1998). The spider fauna of Scragh Bog in Co Westmeath, Ireland (Arachnida, Araneae). Zoologische verhandelingen Leiden 323: 407–415.
Roberts, M. J. (1985). The spiders of Great Britain and Ireland, Volume 3: Colour plates. Harley Books, Colchester, England.
Roberts, M. J. (1987). The spiders of Great Britain and Ireland, Volume 2: Linyphiidae and check list. Harley Books, Colchester, England.
Text written by:
Myles Nolan
iNaturalist: Species account : iNaturalist World Species Observations database