Summary for Eresus sandaliatus (Araneae)
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About this speciesDistribution
This spider was formerly recorded from several heathland areas in the Poole/Bournemouth area, Dorset, and there are unconfirmed reports from Kynance Cove, West Cornwall, in 1932 (Bristowe 1958) and on the Isle of Wight. It is now known from only one natural site in Dorset, a small isolated fragment of heath. Following successful short-distance translocations, it has been introduced to other sites in the area. The UK Biodiversity Action Plan for this spider aims to establish it at up to ten new sites across its natural range (Hughes et al. 2009). The species is rare in northern Europe, recorded from the Netherlands, Germany, Sweden (where it is included on their Red List (Gärdenfors 2000)) and Denmark (as E. cinnaberinus), but it is fairly frequent in parts of the Alps and Pyrenees.
Habitat and ecology
Dry sandy heathland with some bare or lichen covered patches. Shelter from wind is probably necessary, and a south facing slope is an advantage. The spider builds a silk-lined burrow about 10 cm deep covered by a small silk and debris 'roof'. Well-drained soil is essential. The burrows are usually found in open patches. The life cycle takes at least four years. One batch of eighty to ninety eggs is laid. The young remain in the mother's burrow over the first winter, until the sixth instar. Males are active in early May. Females and young feed from April to early June and in August and September, aestivating in late June and July. The food is mainly beetles and spiders (including male Atypus affinis), and ants when the spider is young.
UK Biodiversity Action Plan priority species. Protected under the Wildlife and Countryside Act 1981. One of the rarest and most spectacular of British spiders, thought to be extinct in Britain until rediscovered in 1979. Historically the spider had a very restricted geographic range and is now known from a single natural location. While the population size has increased from just five in 1980 to 1,175 webs counted in 2006, this fell back to 825 in 2007, and the species remains conservation dependent (Hughes et al. 2009). Clearly most of these webs belong to immature spiders but the proportion is unknown. A life cycle of at least four years suggests that fewer than 25% of the webs would belong to adults. Even allowing for the greater visibility of larger, adult webs it would be safe to estimate the population size of mature adults to be less than 2500. All sites require further management to ensure their survival and further translocations are recommended until there are at least 10 sites. From then on, management, monitoring and research should be continued to assess natural progress and to formulate techniques for improving the status of Eresus in the UK (Hughes 2010).
The site is a small isolated fragment of heath. Threats to the habitat include encroachment onto the heathland by the surrounding rhododendrons and pine trees, fire, and loss of heather from infestations of the Heather Beetle Lochmaea suturalis (Thomson). This species is fully protected by inclusion in Schedule 5 of the Wildlife and Countryside Act 1981, which prohibits, among other things, taking specimens without a licence.
Management and conservation
There is an agreement with the Forestry Commission on the conservation and management of the site. Natural England has erected a fence around the site. Nearly all pine trees and rhododendrons have been removed, leaving just a few to provide shelter. Further research into the biology and habitat requirements of the species is ongoing, and annual monitoring of numbers has been carried out. The species is being introduced to other sites in Dorset across its natural range.
Text based on Dawson, I.K., Harvey, P.R., Merrett, P. & Russell-Smith, A.R. (in prep.). References
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