Summary for Robertus insignis (Araneae)
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About this speciesRecorded altitude range
In Britain, this species was originally recorded in 1907 from a male collected at a locality given as Norwich, East Norfolk by Pickard-Cambridge (1907). It was then not recorded again until 1988, when another male was taken in Catfield Fen, about 15 miles north-east of Norwich (Procter 1990). In Europe it appears to be rare throughout its range and has been recorded from a very few individuals in Germany, Estonia and Sweden, where it is included in their Red List (Gï¿½rdenfors 2000).
Habitat and ecology
Nothing was recorded of the habitat in which the first British specimen was found. The second was trapped at ground level in a Cladium sedge-bed, between 21 June and 5 July. In Germany it was taken in May 1959 in a flat fen meadow (Wiehle 1960). In Sweden, five males and 19 females were collected at Knisa Mere, a Cladium mire bordered by Carex tussocks and moss (Almquist 1978).
Very rare, recorded from a single location in 1988. Intensive survey of sites in Broadland, including Catfield Fen, between 2007 and 2009 produced no further records (Lott et al., 2010) but the previous rediscovery of this species after an 80-year gap in the records may indicate that it still survives in other East Anglian fenland sites.
Catfield Fen lies within an SSSI. Because so little is known of the microhabitat requirements and ecology of this species, the exact nature of threats to it remain unclear. In the Broadland area of East Norfolk, sedge-beds have suffered considerable degradation since the beginning of the last century resulting from eutrophication of waterways, water abstraction, land drainage and abandonment of traditional mowing of fen vegetation which in turn leads to scrub and carr woodland encroachment. Which, if any, of these threats have impacted R. insignis populations is unknown.
Management and conservation
The sedge beds at Catfield Fen are being managed by regular mowing. This traditional management regime is being promoted elsewhere in the region by the Broads Authority and other conservation authorities and may help to conserve potential habitat for this species.
Text based on Dawson, I.K., Harvey, P.R., Merrett, P. & Russell-Smith, A.R. (in prep.). References
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