Spiders and Harvestmen

Image above by Matt Prince

Moon spider Callilepis nocturna - Endangered and nationally rare

This spider is known from only three sites in Great Britain, one of which is in Devon: Prawle Point together with Signalman’s Point. The Moon Spider lives on sea cliffs and slopes, running over sandy banks and rocks, and is a specialised ant predator. Populations currently appear stable. Since it requires bare, sunny, ground, this spider would be threatened by scrub encroachment. Prawle Point is the location for many other rare invertebrates including the Long-horned Bee, another Devon Special Species; as such, the spider may benefit from the “Life on the Edge” project – a South Devon AONB/Buglife partnership project.

Map to show the Devon distribution of this species

Image above by John Walters
Hedgehog harvestman Centetostoma bacilliferum - Endangered and nationally rare

In the UK this harvestman is only known from Plymouth where it was first discovered in 1990. It has yet to be found anywhere else in the world. A handsome beast, with black spines and metallic gold patches on its body, the Hedgehog Harvestman lives in scrubby brownfield land, notably a disused railway that served a limestone quarry. It can be found by looking under stones and other debris. John Walters is monitoring the harvestman and populations appear stable. Buglife has worked with Plymouth City Council to avoid a cycle track damaging its core area. Further work to determine the limits of its range is desirable, and whether it occurs anywhere outside the city limits.
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Image above by John Walters
Horrid ground weaver spider Nothophantes horridus - Endangered globally and nationally rare

This tiny money spider is known in the world only from a handful of sites in Plymouth, Devon. It is usually found under stones and debris on the floor and cliff faces of disused limestone quarries. The spider’s name comes from the fact that its body and legs are rather hairy – the Latin origin for the word horrid is bristly. Buglife has been surveying known sites and has also found the species in recent years in a few further sites in Plymouth with similar ecological conditions. Buglife has also been undertaking ecological research into its precise habitat requirements. The Horrid Ground Weaver is threatened by development – indeed, one of the three sites it was originally known from was lost in the late 1990s to an industrial park. Fortunately, a planning application for a housing development at another site, Radford Quarry, was turned down in 2015, partly for biodiversity reasons including the presence of the Horrid Ground Weaver. In 2019, John Walters reported that the spider was still present in good numbers at Billacombe and it remained present at Cattedown, a new site discovered in December 2018.

Map to show the Devon distribution of this species

Image above by John Walters
Lichen running spider Philodromus margaritatus - Nationally rare and rapidly declining

Devon is one of two UK strongholds for this crab spider, the other being north-west Scotland. Camouflaged to look like lichen, the spider is associated with mature lichen-covered trees, both broadleaved and conifer, in woodlands and orchards. In Devon it is known from a few sites in the southern half of the county, mainly from Dartmoor. In December 2019, John Walters found a good population in an organic cider orchard near Landscove in southern Devon – the apple trees were covered with lichens. The spider is at risk from the felling of mature lichen-covered trees, and from any lack of younger, successor, trees. Trends in range or population in Devon are currently unknown.
Map to show the Devon distribution of this species

Sources of further information:

British Arachnological Society

Spider and Harvestman Recording Scheme