SPIDERS AND PHALANGIDS OF INCHCAILLOCH, LOCH LOMOND I - GENERAL CONSIDERATIONS

By DAVID J. CURTIS
Department of Biology, Paisley College of Technology

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Introduction

The island of Inchcailloch is situated close to Balmaha in the south-eastern part of Loch Lomond (O.S. grid reference NS410905) and forms part of the Loch Lomond National Nature Reserve. The island is covered with semi-natural deciduous and coniferous woodland, together with a rich understorey vegetation. Most of the data on the spiders and phalangids have heen obtained by means of pitfall traps and thus knowledge is most detailed for the ground-active fauna. This information together with some obtained by other sampling techniques is presented here.

A pitfall sampling program commenced in the late summer of l97l and is still in progress. At each of four sites, twenty small plastic jars were sunk into the ground to capture surface-active invertebrates. The traps were emptied at approximately weekly intervals for the first year and thereafter at monthly intervals.

Sites

Site 1 is located in oak Quercus robur woodland; the field and ground layer vegetation includes Luzula sylvatica (Huds.) Gaud, Pteridium aquilinum (L.) Kuhn, Agrostis stolonifera L., Rubus fruticosus agg., Poa sp., Dryopteris sp., Endymion non-scriptus (L.) Garcke, Oxalis sp. The soil at this site is an acid brown earth overlying lower old red sandstone and conglomerates.

Site 2 is an alder carr in which the field layer and ground layer vegetation includes Luzula sylvatica, Agrostis stolonifera, Rubus fruticosus, Dryopteris sp., Endymion nonscriptus, Oxalis sp., Deschampsia caespitosa (L.) Beauv., Nasturtium microphyllum (Boem.) Rchb., Galium palustre L., Veronica chamaedrys L., Lonicera periclymenum L., Filipendula ulmaria (L.) Maxim., the moss Thuidium tamariscinum, as well as Pteridium aquilinum. The substrate in the alder carr is a poorly drained acid peaty soil, again over lower old red sandstone.

Site 3 is located near the summit of the North Hill amidst mainly Pinus sylvestris, together with some birch and rowan. The ground and field layer vegetation around this site includes Deschampsia flexuosa (L.) Trin., Calluna vulgaris (L.) Hull, Vaccinium myrtillus L., Luzula sylvatica, Polypodium vulgare L., as well as several mosses such as Dicranum majus, Dicranum scoparium, Dicranella beteromalla, Leucobryum glaucum, Lophocolea cuspidata, Bazzania trilobata, Hypnum cupressiforme, and nearby clumps of Pteridium aquilinum. The soil of the North Hill is a very acid peaty ranker overlying old red sandstone and conglomerates.

Site 4 is situated in the Central Valley in woodland comprising mainly Quercus robur, as well as other deciduous trees such as hazel. The field layer here includes mostly Rubus fruticosus with some Pteridium aquilinum, Dryopteris sp., Oxalis sp., Melandrium rubrum (Weig.) Garcke, Deschampsia caespitosa, growing in an acid brown podzolic soil overlying old red sandstone and conglomerates.

The four sites studied by pitfall sampling thus have contrasting field and ground layer floras, as well as different canopy species and although the soils vary they are all acid soils overlying lower old red sandstone. Of the two oak-dominated woodland stations, site 4 is considerably wetter than site 1, though not as wet as site 2 in the alder carr. Site 3 differs from the other sites largely in the presence of dense clumps of mosses, as well as Calluna and Vaccinium plants which persist throughout the winter months, in contrast to the other sites where most of the aerial plant structures diminish during the winter.

Harvestmen

Eleven species of harvestmen have been taken on the island. These are listed in Table 1. Most of these appear to be fairly generally distributed over the island and are mainly inhabitants of the ground and lower field layers. Megabunus diadema is a beautiful harvestman which occurred in the pitfall traps rather surprisingly as its usual habitat on the island is the trunks of trees and rock surfaces, in which places it blends extremely well with lichens. One surprising omission from the list of phalangids is Leiobunum rotundum (Latreille) which does occur on the eastern banks of Loch Lomond and would he expected on the bushes and trees of Inchcailloch.

Spiders

Spiders are represented by 101 species captured to date, approximately 70% of which belong to the family Linyphiidae. Members of the families Dictynidae, Dysderidae, Gnaphosidae, Clubionidae, Anyphaenidae, Thomisidae, Lycosidae, Agelenidae, Theridiidae, Tetragnathidae and Argiopidae are listed in Table 2, while the linyphiids are given in Table 3.

Some of the spiders occurred in relatively large numbers at all four pitfall trap stations, e.g. Walckenaera acuminata, Monocephalus fuscipes, Centromerus sylvaticus, Lepthyphantes zimmermanni. Species such as Lycosa lugubris, Micrargus herbigradus, Oreonetides abnormis, Macrargus rufus and Lepthypnantes tenuis occurred in moderate quantities at all the sites, while very small numbers of some species were taken at most of the sites, e.g. Trochosa terricola, Trachynella nudipalpis, Gongylidiellum vivum, Erigonella hiemalis, Porrhomma pallidum and Lepthyphantes minutus. Spiders which appeared fairly abundantly in traps at all sites but which were most common at a particular site include Gonatium rubellum (at site 3), Tapinocyba pallens (at site 3), Diplocephalus picinus (mostly at site 1, absent from site 3), Microneta viaria (at site 1) and Lepthyphantes alacris (at site 3). Hahnia helveola and Hilaira excisa showed restricted occurrence, being trapped in moderately large numbers at stations 3 and 2 respectively and absent from the other sites. Rare species taken at only one site include Drassodes pubescens (Site 3), Tarentula pulverulenta (site 1), Theridion vittatum (site 1), as well as Cornicularia cuspidata (Site 3), Cnephalooctes obscurus (site 2), Diplocephalus cristatus (Site 3) and Leptorhoptrum robustum (site 2).
An indication of the frequency distribution of the spider species is shown in Figure 1.

Some of the rare species captured are of great interest, being rare but widespread, e.g. Jacksonella falconeri, Sintula cornigera and Theonoe minutissima, or even rare and restricted in distribution, e.g. Agyneta ramosa (known from a few English courties and a Welsh county) and Wideria polita and Micaria subopaca which have previously been recorded only from southern and eastern England. Other species taken in small numbers in the pitfall traps are more abundant in habitats other than the ground layer. Thus Ciniflo fenestralis, Cryphoeca silvicola and Segestria senoculata have been captured in the corrugated paper traps used to study tree trunk spiders (Curtis and Morton; 1974), while other species such as Linyphia triangularis, Meta segmentata and Tetragnatha montana are known to occur in great numbers in the field layer vegetation and only relatively rarely enter the ground layer. Oxyptila trux is a crab spider which occupies the field layer vegetation and has only once been captured in the pitfall traps.

The list of spiders and harvestmen considered here is undoubtedly only an incomplete representation of the entire island species. Several immature specimens from genera such as Zygiella and Philodromus have been captured and could not be determined to species level because of their lack of genitalia. More intensive sampling of strata other than the ground layer will probably yield additions to the species list as also will continuance of the pitfall trapping schedule. More detailed analysis of the data obtained will be published at a later date.
 

Acknowledgements

I am grateful to colleagues in the Department of Biology, especially Dr. J.C. Smyth and Mr. J.D. Hamilton, for advice and useful discussions, and to Mr E. Morton for assistance in the field. Thanks are also due to Dr. J.H. Sparling for aid in plant identification and to the Nature Conservancy in the persons of Mr. E.T. Idle and Mr. C. Placido and Mr. J. Mitchell, for permission to trap on the island and various assistance.
 

Reference

CURTIS, D.J. and MORTON, E. (1974). Notes on spiders from tree trunks of different bark texture; with indices of diversity and overlap. Bull. Brit. Arachnol. Soc., 3: 1 - 5.
 

Fig. 1

Frequency distribution of spiders taken in pitfall traps on Inchcailloch, 1971-72.

The height of each column in the histogram is proportional to the frequency, F, of species, i.e. the number of species represented by N individuals, indicated along the abscissa in classes of size 10.

The highest column thus indicates 64 species represented by between one and ten individuals captured, while only one species (Monecephalus fuscipes) was represented by 300-310 individuals.

TABLE 1: INCHCAILLOCH PHALANGIDS
 

Species	Pitfall trap sites
	1	2	3	4
Nemastoma bimaculatum (Fabricius)	+	+	+	+
Nemastoma chrysomelas (Hermann)	+	+	+	+
Mitopus morio (Fabricius)	+	+	+	+
Oligolophus agrestis (Meade)	+	+	+	+
Oligolophus tridens (C.L.Koch)	+	+	-	-
Oligolophus hanseni (Kraepelin)	+	+	+	+
Odiellus palpinalis (Herbst)	+	+	+	+
Odiellus meadei (Cambridge)	+	+	+	+
Lacinius ephippiatus (C.L.Koch)	+	+	-	+
Platybunus triangularis (Herbst)	+	+	+	+
Megabunus diadema (Fabricius)	-	+	+	-

+ indicates presence

TABLE 2: INCHCAILLOCH SPIDERS - Families Dictynidae - Argiopidae

Species	Pitfall trap sites				Other habitats
	1	2	3	4
DICTYNIDAE:
Ciniflo fenestralis (Stroem)	-	+	+	-	tree trunks
C. similis Blackwall	-	-	+	-
DYSDERIDAE:
Harpactea hombergi (Scopoli)	-	-	-	-	tree trunks
Segestria senoculata (L.)	-	-	+	-	tree trunks
GNAPHOSIDAE:
Drassodes pubescens (Thorell)	-	-	+	-
Micaria subopaca Westring	+	-	-	-
CLUBIONIDAE:
Clubiona compta C.L.Koch	-	-	+	-	tree trunks
Agroeca proxima (O.P.-Cambridge)	-	-	+	-
ANYPHAENIDAE:
Anyphaena accentuata (Walckenaer)	+	-	+	+	tree trunks
THOMISIDAE:
Oxyptila trux (Blackwall)	-	-	+	-
LYCOSIDAE:
Lycosa pullata (Clerck)	-	+	-	-
L. lugubris (Waickenaer)	+	+	+	+
Tarentula pulverulenta (Clerck)	+	-	-	-
Trochosa torricola Thor.	-	+	+	+
Pirata hygrophilus Thor.	-	+	-	+
AGELENIDAE
Cryphoeca silvicola (C. L. Koch)	+	-	-	+	tree trunks
Hahnia montana (Blackwall)	-	-	+	-
H. helveola Simon	-	-	+	-
THERIDIIDAE:
Theridion vittatum C. L. Koch	+	-	-	-
T. pallens Blackwall	+	+	-	-
Robertus lividus Blackwall	+	+	-	-	tree trunks
Theonoe minutissima (O.P. -Cambridge)	-	-	+	-
TETRAGNATHIDAE:
Tetragnatha extensa (L.)	-	-	-	-	woodrush in alder carr
T. montana Simon	-	-	+	-	tree trunks
T. obtusa C.L.Koch	+	-	-	-
Pachygnatha listeri Sund.	+	-	+	-
P. degeeri Sundevall	-	-	-	-	moss under heather
ARGIOPIDAE:
Meta segmentata (Clerck)	-	+	-	+
M. segmentata mengei (Blackwall)	+	+	-	-
M. merianae (Scopoli)	+	-	-	+
Araneus diadematus Clerck	-	-	-	-	on heather
A. umbraticus Clerck	-	-	-	-	tree trunks
A. cucurbitinus Clerck	-	-	-	-	on wooden post

TABLE 3: INCHCAILLOCH SPIDERS -

Family Linyphiidae

Species	Pitfall trap sites				Other habitats
	1	2	3	4
Ceratinella brevipes (Westring)	+	+	+	-	tree trunks
C. brevis (Wider)	-	-	+	-
Walckenaera acuminata Blackwall	+	+	+	+
Wideria cucullata (Koch)	-	+	+	-
W. fugax (O.P.-Cambridge)	-	-	+	-
W. polita (Simon)	-	-	+	-
TrachynelIa nudipalpis (Westring)	+	+	+	-
Cornicularia cuspidata (Blackwall)	-	-	+	-
Dicymbium nigrum (Blackw.)	-	+	-	-
D. tibiale (Blackwall)	+	+	-	-
Gongylidium rufipes (Sundevall)	-	-	+	+
Dismodicus elevatus (Koch)	+	-	-	-
Hypomma cornutum (Black.)	+	-	-	-
Gonatium rubellum (Black.)	+	+	+	+	tree trunks
Maso sundevalli (West.)	-	-	-	+
Pocadicnemis pumila (Blackwall)	-	+	+	-
Lophocarenum nemorale (Blackwall)	-	-	-	-	tree trunks
Cnephalocotes obscurus (Blackwall)	-	+	-	-
Tapinocyba pallens (0. P. -Cambridge)	+	+	+	+
Thyreosthenius parasiticus (Westring)	-	-	-	-	tree trunks
Monocephalus fuscipes (Blackwall)	+	+	+	+	tree trunks
M. castaneipes (Simon)	-	+	-	+
JacksonelIa falconeri (Jackson)	+	+	-	-
Gongylidiellum vivum (O.P. -Cambridge)	+	-	+	+
Micrargus herbigradus (Blackwall)	+	+	+	+
Erigonella hiemalis (Blackwall)	+	+	-	+
Savignia frontata (Black.)	-	-	-	-	tree trunks
Diplocephalus cristatus (Blackwall)	-	-	+	-	tree trunks
D. Iatifrons(O.P. -Camb.)	+	+	-	+
D. picinus (Blackwall)	+	+	-	+
Caledonia evansi (O.P.-C.)	-	-	-	-	tree trunks
Erigone dentipalpis (Wider)	+	-	-	+
E. atra (Blackwall)	-	-	-	+
Leptorhoptrum robustum (Westring)	-	+	-	-
Hilaira excisa (O.P.-C.)	-	+	-	-
Porrhomma pygmaeum (Blackwall)	-	-	+	-
P. pallidum Jackson	+	+	+	+
P. montanum Jackson	-	-	+	-
Agyneta conigera (O.P.-C.)	-	-	+	-
A. ramosa Jackson	-	-	+	-
Microneta viaria (Black.)	+	+	+	+
Maro minutus O.P.-Camb.	+	-	+	-
Centromerus sylvaticus (Blackwall)	+	+	+	+
C. prudens (O.P.-Camb.)	-	+	-	-
C. dilutus (O.P.-Camb.)	+	+	+	+
Sintula cornigera (Blackwall)	+	-	+	-
Oreonetides abnormis (Blackwall)	+	+	+	+
0. firmus (O.P.-Camb.)	+	-	+	-
Macrargus rufus (Wider)	-	-	+	-
Bathyphantes dorsalis (Wider)	-	-	+	-
B. concolor (Wider)	-	+	-	+
B. gracilis (Blackwall)	-	+	-	-
Drapetisca soclalis (Sundevall)	-	-	-	-	tree trunks
Lepthyphantes minutus (Blackwall)	+	+	+	+
L. alacris (Blackwall)	+	+	+	+
L. obscurus (Blackwall)	-	-	+	-
L. tenuis (Blackwall)	+	+	+	+
L. zimmermanni Bertkau	+	+	+	+
L. mengei Kulczynski	+	-	+	-
L. tenebricola (Wider)	+	+	+	+
L. ericaeus (Blackwall)	-	+	-	-
L. pallidus (O.P.-Camb.)	+	+	+	+
L. angulatus (O.P.-Camb.)	-	-	+	-
Helophora insignis (Blackwall)	+	+	+	+
Linyphia triangularis (Clerck)	-	-	+	+	abundant on woodrush
L. peltata Wider	+	+	+	+	tree trunks
L. hortensis Sundevall	+	-	+	+
Mengea scopigera (Grube)	+	-	-	-

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