The potential extinction of a not so horrid spider

Vanessa Amaral-Rogers is the Campaigns Officer for Buglife. After finishing her Masters in Conservation Biology at the University of Derby on bat ecology, she now works on science communications, legislation, pesticides and pollinators.

In a quarry in the South-West of England, a small spider lurks. The Horrid ground weaver (Nothophantes horridus) may not have the best name (not because it’s particularly unpleasant but because horridus means bristly in Latin) but that hasn’t stopped this tiny money spider from causing quite a stir. Very little is known about it except that for whatever reason, it only lives in two sites in Plymouth and nowhere else in the world. Now, one of the sites, Radford Quarry, is under threat from destruction.

Radford Quarry was classed of high ecological value as exhibited by its County Wildlife Site status and is the only remaining disused limestone quarry in the area that has returned to nature. Not only is the old quarry home to this incredibly rare spider, it is a haven for other bugs and wildlife. The plans to build 57 new houses here were objected to by Buglife and refused by Plymouth City Council last year but the applicant has appealed the decision.

The Horrid Ground Weaver is quite possibly, the world’s rarest spider. There is very little existing knowledge of the ecology of the species, the spider is tricky to find due to its size and its habitat of living deep in the cracks and crevices in the limestone. However, it is thought that the species is a nocturnal hunter, hunting on the scree slopes surrounding the quarry most likely feeding on springtails and other small prey.

Listed under Section 41 of the Natural Environment and Rural Communities Act, it is acknowledged that its conservation is a national concern. However there are currently no guidelines available for how to deliver this (in common with the majority of invertebrate species added to the UKBAP priority species list in the most recent review – 2004) due to the lack of habitat and ecological data on the species.

So given that the Horrid ground weaver is only known from two sites in the world, let me recount our UK obligations to biodiversity. At the Nagoya UN Biodiversity Summit in October 2010, 192 countries and the European Union agreed to an ambitious conservation plan to protect global biodiversity. Parties agreed on a set of strategic goals and targets (the ‘Aichi’ targets) to drive action on biodiversity of which we are signed up to. One of these targets states that by 2020 the extinction of known threatened species has been prevented and their conservation status, particularly of those most in decline, has been improved and sustained.

Horrid Ground Weaver (Nothophantes horridus)

One of the most elusive spiders in the UK, the Horrid Ground Weaver has now been captured on film, confirming the existence of two new colonies.

The species lives in limestone cracks, and is most often nocturnal. Its prey is likely to be springtails or other small insects. The latest colonies were found near Plymouth, in the county of Devon, southern England.

The genus Nothophantes horridus is very difficult to spot, as the spider is small and only a few millimetres long. It only comes out during the night, but it is not difficult to identify, owing to its bristly body.

Project documents

• photograph of survey work
• photograph of survey work
• photograph of survey work

Project 150511062 location - United Kingdom, Europe

Project number: 150511062

Awarded amount: $5,000

Awarded date: 01-11-2015

Continent: Europe

Country: United Kingdom

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Rosser’s Sac Spider (Clubiona rosserae)

The Rare Rosser’s Sac Spider UK is back! The sac spider was thought to be extinct in the UK until recently. It was last seen at Lakenheath Fen in Suffolk.

The species is listed as a Priority Species in the UK Biodiversity Action Plan, and is under threat across East Anglia where it lives. Conservationists are working to save this amazing species from extinction by improving management of fenland habitats.

The rare Rosser’s sac spider is a member of the clubionid family. It lives in a tubular silk retreat, hidden inside a folded leaf. It is one of the most unusual spiders in the UK. It is believed to hunt for prey without using its web.