SPIDERS, HARVESTMEN AND PSEUDOSCORPIONS

P. Smithers

The arachnids are an ecologically important group of predators and scavengers which often dominate the ground fauna of terrestrial habitats. The predatory nature of most members of this group mean they exert a powerful limiting influence on populations of other invertebrates, thus playing an important part in maintaining a natural balance in terrestrial communities. Whilst the presence of over half of the British arachnid species indicates the richness of Cornwall’s fauna, the number of records for each species is very low, even for two of our commonest spiders - the Garden Cross Spider Araneus diadematus Clerck and Meta segmentata (Clerck). It is therefore difficult to determine whether species which are nationally rare are also scarce in Cornwall or merely under-recorded and conversely if the apparent rarity of some nationally common species is a true indication of their status within Cornwall. In order to redress this situation more records are urgently required. Maps of the known distribution of Cornish spiders can be found at the late Steve Hopkin’s site, http://www.stevehopkin.co.uk/cornishspiders/ The UK and world distribution of the British spider fauna can be found at http://www.britishspiders.org.uk/html/bas.php Maps of the British distribution and notes on the biology of British spiders can also be found in the Provisional Atlas of British Spiders, Ed. Harvey, Nellist & Telfer (2002). The national status of species included in this review were taken from Bratton (1991) and Merritt (1990) for the spiders and direct from JNCC (D. Proctor, pers. comm.) for the harvestmen and pseudoscorpions. Information on the habitats and ecology of spiders was taken from Bratton (1991), Merritt (1990), Roberts (1985) and Locket & Millidge (1951). For harvestmen, Hillyard & Sankey (1989) was consulted, and for pseudoscorpions Legg & Jones (1988). In order to utilise the largest data set possible the following review is based on records from 1900 onwards. Records are from the CBRU. database unless otherwise indicated. I would like to thank Dr Peter Merrett for his records and comments regarding the rarer spiders of Cornwall and JNCC for information regarding the national status of harvestmen and pseudoscorpions. Thanks also go the Keith Alexander for his advice on the pseudoscorpion section of this chapter.

1. Spiders

1.1. Red Data Book Spiders

Eresus sandaliatus Ladybird Spider

Lathys stigmatisata

Gnaphosa occidentalis

Clubiona genevensis

Episinus maculipes

Pseudomaro aenigmaticus

1.2. Nationally Scarce/Notable Spiders

Segestria bavarica

Agroeca cuprea

Liocranum rupicola

Ozyptila blackwallii

Ozyptila scabricula

Euophrys herbigrada

Talavera petrensis

Sitticus caricis

Pardosa agricola f. arenicola

Pardosa agrestis

Trochosa robusta

Ero tuberculata

Episinus truncatus

Dipoena prona

Dipoena inornata

Anelosimus aulicus

Achaearanea simulans

Achaearanea veruculata

Theridiosoma gemmosum

Tetragnatha pinicola

Tetragnatha striata

Araneus angulatus

Zilla diodia

Argiope bruennichi

Walckenaeria incisa

Acartauchenius scurrilis

Trichoncus saxicola

Tapinocyba mitis

Micrargus laudatus

Mioxena blanda

Neriene furtiva

1.3. Locally Scarce Spiders

Scytodes thoracica

Dolomedes fimbriatus

2. Harvestmen

Anelasmocephalus cambridgei

Paroligolophus meadii

Nelima gothica

3. Pseudoscorpions

Chthonius orthodactylus

Chthonius tetrachelatus

Neobisium maritimum

Dinocheirus panzeri

Dactylochelifer latreillei

Lamprochernes chyzeri