Spiders and harvestmen

Over 450 species of spiders and harvestmen have been recorded in Devon.

As well as being an important food source for other wildlife, spiders and harvestmen feed on other invertebrates, helping to control pest species.

The Horrid Ground-weaver spider is found in limestone quarries around Plymouth and nowhere else in the world.

What we need to do and where

Euophrys petrensis (a Teign Valley rock spider), A. Cunningham

Horrid ground weaver (Plymouth spider group), John Walters

A small yellowy-brown spider with black eyes can be seen against a blurred green background.

Maro lepidus female, Tylan Berry

1. About

Spiders and harvestmen are arachnids, an ancient group of creatures with ancestors that lived more than 420 million years ago. Unlike insects, arachnids have four pairs of legs instead of three, simple rather than compound eyes, and no antennae or wings. Spiders differ from harvestmen as they have two distinct body segments rather than one, and because they produce silk. Spiders weave their silk to make webs to catch prey, to build retreats, to protect their eggs and to disperse on air currents.

Arachnids eat insects so help to control species which damage crops or spread disease. They’re also an important food source for birds, mammals, amphibians and reptiles.

Devon’s spiders and harvestmen can be found almost everywhere, from the coast to high moorland, in gardens and in our homes. Numbers vary widely according to habitat, but it has been estimated that there can be up to 800 spiders per square metre in uncut grassland. Spiders and harvestmen all need:

Food: Spiders are carnivores and feed on live invertebrates. They inject their prey with venom and eat them by sucking up liquid nutrients. Harvestmen have chewing mouthparts and so can eat live and dead invertebrates, as well as decaying plant matter.

Shelter: Spiders and harvestmen hide from predators and build webs or retreats among vegetation, in trees, under rocks and inside buildings.

Currently around 680 species of spider and 30 species of harvestmen are found in the UK. Over 450 of these have been recorded in Devon and 29 are listed as Devon Species of Conservation Concern. Those identified as Devon Special Species are discussed below.

Key pressures and opportunities

Species in this group have different needs so pressures and opportunities are discussed for each Devon Special Species and in the relevant habitat pages. 

2. What we need to do and where

Priority

Increase the abundance and distribution of spiders and harvestmen across Devon, particularly those identified as Devon Special Species.

See Find out more below for links to more detailed information on this group including management advice and records.

Devon Special Species

A small yellowy-brown spider with black eyes can be seen against a blurred green background.

Dartmoor bog spiders

Read more

This group of spiders is found in the acidic wetlands of Dartmoor, including large upland peat bogs, smaller valley mires, and along streams modified by old tin works. All the sites that support these spiders are within the North and South Dartmoor SSSIs. Good examples include Foxtor Mires (near Whiteworks disused tin mine) and Raybarrow Pool (below Little Hound Tor).

The specific habitat needs of this group are poorly understood, but the species are likely to be sensitive to anything that damages bog or mire health, including climate change, fire, atmospheric pollution or changes to water levels and quality. Eight species in this group are listed as Devon Species of Conservation Concern. Two of these are identified as Devon Special Species. See Find out more below for a link to the detailed profile written for this group.

A spider specimen viewed under a microscope can be seen against a blue background. The spider is a yellowy-brown with a large abdomen and relatively short legs.

A money spider

Centromerus levitarsis

In Britain this spider is only found on Dartmoor (Foxtor Mires and Muddilake) and at lowland raised bogs in Cumbria and Scotland. The Devon population is isolated and vulnerable to local extinction. Further study is needed to better understand the needs and behaviour of this spider, and whether it occurs more widely on Dartmoor than is currently known.

A small spider can be seen against a white, web-like background. The spider is yellowy-brown with its legs clearly displayed as well as a pair of pincers at the front of its head.

A money spider

Maro lepidus

This rare money spider occurs in Wales, northern England and Scotland but in southern England is only known from Dartmoor (New Bridge and Taw Marsh) and Bodmin Moor.

Actions

Protect and restore Dartmoor bogs and valley mires for rare spiders. 

  • Be aware of rare spiders when managing this habitat. Otherwise, actions are to maintain and restore healthy bogs and mires through, for example, light grazing and rewetting (blocking drainage channels). Manage surrounding land to maintain clean water and hydrological processes. See Heath, moor and mire mosaics for more information.

Where to focus actions

High Opportunity Areas: Dartmoor flushes and mires (existing) and Dartmoor deep peat. See Mapping.

Yellow-striped Bear-spider

Arctosa fulvolineata
Read more

The Yellow-striped Bear-spider is a relatively large wolf spider that’s confined to saltmarshes in southern and eastern England. On the west coast it’s only found at Yelland in North Devon. This isolated population on the Taw Estuary (within the SSSI) inhabits less than 750 m2 across two areas, near the old Yelland Power Station and at the western end of Isley Marsh.

The spider is associated with unvegetated areas of estuarine foreshore, where it lives under stones embedded in the mud. The spiders form silk retreats in gaps under the stones, which are covered during the highest tides.

Threats to the species include sea level rise due to climate change, increased storms causing erosion, isolation (the nearest population is in Hampshire), and damage to habitat from development, particularly coastal defences.

Actions

Maintain open habitat on the Taw estuary mudflats at Yelland for the Yellow-striped Bear-spider.

  • Protect habitat that the spider uses or could potentially use. Coastal realignment schemes in or near the species zone should get expert advice and create new habitat with embedded stones on the estuary foreshore.
  • Survey other areas of upper saltmarsh on the Taw Estuary, east to Penhill Point (SS517.343) and on the northern shore at Horsey Island (SS480.334).

Where to focus actions

High Opportunity Area: Taw estuary mudflats at Yelland – Cornwall to Morte Point Coastal Wildbelt. See Mapping. 

Plymouth arachnids

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The three species in this group depend on rocky sites in and around Plymouth. Two are Devon Special Species. The Hedgehog Harvestman is not found elsewhere in the UK, and the Horrid Ground-weaver has not been found anywhere else in the world.

The third species in this group is Scotolemon doriae, a small, mite-like harvestman. It can be found under rocks embedded in the soil. In 2016 it was discovered new to the UK at Radford Quarry in Plymouth and has since been found at Ford Park Cemetery in Plymouth, in Bristol and Falmouth.

For more information on this group see the LNRS profile in Find out more below.

Horrid Ground-weaver

Nothophantes horridus

This small money spider was discovered in 1989 at Cattedown Quarry. It has a rather hairy body and legs: the meaning of the word horridus in its Latin name is bristly. The species has been found under rocks in Cattedown, Billacombe and Radford limestone quarries and it may be at other sites nearby. It’s not known to occur anywhere else in the world. The main threat to the species is from the development of old quarries. It’s active in winter so may be overlooked and could occur in other limestone areas on the west coast of Europe.

Spiky small bodied spider with long thin legs

Hedgehog Harvestman

Nemastomella bacilliferum

A small harvestman with distinctive spines on its body. In the UK it’s only found in Plymouth (at Billacombe, Radford Wood, Ford Park Cemetery and in the Forder Valley). It can be found sheltering in grass tussocks and on the underside of rocks. The main site at Billacombe is owned by Plymouth City Council and managed for the Horrid Ground-weaver spider, which should also benefit this species. The Hedgehog Harvestman is a great flagship species as it highlights the importance of nature reserves around Plymouth.

Actions

Manage Plymouth green spaces and quarries for rare spiders by protecting and creating open rocky areas and allowing tussocky grasses to develop.

  • Continue to research the ecology of the Horrid Ground-weaver and to survey sites across Plymouth (with a focus on limestone areas) to better understand the distribution of these species.

Where to focus actions

High Opportunity Areas: Cattedown Quarry, Billacombe, Radford limestone quarry, Radford Wood, Ford Park Cemetery (a map of the spider areas is being produced with PCC and will be added to the viewer). See Mapping.

Moon spider and other Prawle cliff spiders

Read more

Read about this group on the Start Point to Bolt Tail coast invertebrate group page.

Teign valley rock spiders

Read more

The upper Teign valley between Castle Drogo and Steps Bridge is a very important area for rare spiders. At least 127 species have been recorded here, including the Gorge Ground Spider (Civizelotes civicus) which is found nowhere else in Britain, and 17 species that are Nationally Scarce. The best areas are south-west to south-facing sunny slopes with broken shale and thin soils that are partly stabilised by lichens and moss. 

Eight of the 127 species in this group are listed as Devon Species of Conservation Concern. These include the Nationally Rare jumping spider, Euophrys petrensis, which is found in other parts of southern England but hasn’t been seen anywhere else in Devon for over 20 years, and a meshweb spider, Iberina candida, which isn’t found anywhere else in the county.

The requirements of this group overlap with those of Toadflax-leaved St John’s-wort (see Sunny rocky outcrop plants) and at least two nationally rare beetles, Kugelann’s Green Clock Beetle (Poecilus kugelanni) and the click-beetle Cardiophorus vestigialis.

The gorge ground spider (Civizelotes civicus) has been identified as a Devon Special Species.

For more information on this group see the LNRS profile in Find out more.

A ground spider

Civizelotes civicus

This relatively small spider (3.4-5.5 mm) was discovered in the Teign Valley in 2020 and this is the spider’s only known location in Britain. It’s been found on three slopes near Castle Drogo (managed by the National Trust) and two at Dunsford (part of the Teign Valley Woods SSSI managed by Devon Wildlife Trust) and is currently known from 400 m2 of potentially 1 km2 of discontinuous suitable habitat. 

Unlike spiders that construct webs, ground spiders are active hunters and instead weave silk retreats and lay eggs under small pieces of broken shale. However, we do not know much about this species and there is a lot still to learn.

Actions

Maintain and expand sunny rocky outcrops for rare spiders through scrub control and light grazing.

  • Where possible survey other nearby rocky slopes for potential populations of the gorge ground spider.

Where to focus actions

High Opportunity Areas: Upper Teign valley rocky outcrops (unmapped). Mapped as a Species Opportunity Area. See Mapping 

Actions for all spiders and harvestmen

Habitat management and creation

Spiders and harvestmen are found in most habitats across Devon and will benefit from the actions set out on the Habitats pages.

Anyone who is managing or creating habitat for rare spiders and harvestmen should be aware of their needs. For more detailed information see the list of Devon Species of Conservation Concern and Find out more below.

Research and monitoring

Increase research and monitoring for spiders and harvestman.

3. Inspiration

Case studies

Buglife project

Buglife is working closely with Plymouth City Council on a project to manage habitat and survey for the Horrid Ground-weaver spider and Hedgehog Harvestman. This work is funded through Natural England’s Species Recovery Project.

South West Peatland Partnership

The South West Peatland Partnership aims to restore 2,600 hectares of degraded peatland on Dartmoor, Exmoor, Bodmin Moor and West Penwith. While not focused specifically on spiders, it’s a good example of how landscape-scale projects can have multiple benefits, including the restoration of rare and special species.

Dartmoor peat bogs, with machinery in the distance and a low sun

If you’re doing something to help nature thrive, please share it on the Devon Nature Recovery Delivery Map to inspire others to take action.

Where to visit

Always follow the Countryside Code and keep to footpaths and sites that are managed for public access. 

Prawle Point

With crumbling cliffs and wildflower-rich cliff tops, the landscape at Prawle Point is a great place to spot invertebrates. 

Join an event hosted by the Life On The Edge project to learn more about invertebrates on this amazing stretch of coast.

Dartmoor

A huge range of arachnids can be found across Dartmoor National Park due to its diverse habitats that include bogs, ancient woodlands, rocky outcrops and river valleys.

For information on visiting these and other sites that are open to the public, please see the Explore Devon website.

4. Find out more

The Spider and Harvestman Recording Scheme website has information on all species.

The British Arachnological Society website has information about arachnids, including articles and opportunities to get involved.

Buglife’s Bug Directory has lots of information about invertebrates, including spiders and harvestmen. Information on their work on the Horrid Ground-weaver and Hedgehog Harvestman can be found at Horrid Ground-weaver Project – Buglife projects

Devon Species of Conservation Concern list

BOLD if it’s a Devon Special Species, * for Devon Special Group.

  • Acartauchenius scurrilis *
  • Agroeca cuprea *
  • Agyneta cauta *
  • Araeoncus crassiceps *
  • Arctosa fulvolineata
  • Bathyphantes setiger *
  • Callilepis nocturna
  • Centromerus levitarsis
  • Cozyptila blackwalli *
  • Erigone dentigera *
  • Erigonella ignobilis *
  • Euophrys herbigrada *
  • Euophrys petrensis *
  • Euryopis flavomaculata *
  • Gnaphosa lugubris *
  • Haplodrassus silvestris *
  • Iberina candida *
  • Lasaeola prona *
  • Lathys stigmatisata
  • Maro lepidus
  • Mastigusa diversa*
  • Micaria albovittata *
  • Nemastomella bacillifera
  • Nothophantes horridus
  • Phaeocedus braccatus
  • Philodromus fallax
  • Philodromus margaritatus *
  • Phlegra fasciata *
  • Pirata tenuitarsis *
  • Scotolemon doriae *
  • Semljicola faustus *
  • Trochosa robusta
  • Walckenaeria kochi *
  • Walckenaeria nodosa *
  • Zelotes longipes *
  • Zora nemoralis

Photo credits
  • Maro lepidus female 1 – Tylan Berry
  • Centromerus levitarsis female – Richard Gallon
  • Maro lepidus female 2 – Tylan Berry
  • Yellow-striped Bear Spider – Arctosa fulvolineata, Evan Jones
  • Horrid Ground-weaver – John Walters
  • Hedgehog Harvestman – John Walters
  • Calilepis nocturna – Richard Gallon
  • Euophrys petrensis – A. Cunningham
  • Civizelotes civicus – A. Cunningham
  • South West Peatland Partnership – DNPA

Species profiles written for the LNRS

Draft