TRANSACTIONS THE SPIDER FAUNA OF THE HEATHS AND FENS IN WEST SUFFOLK B y E R I C DUFFEY, G . H .
LOCKET a n d A . F .
T h e sandy breck country so well known to East Anglian naturalists Covers a considerable area in north-west Suffolk and south-west Norfolk and borders the eastern edge of the Fenland Basin. Although chiefly famous for the rare plants and animals of the arid heaths, the district has a rieh diversity of habitat from the sandy uplands to the woodlands and fens of the river Valleys. Consequently distinetive plant and animal communities may be found almost side by side. Three main river Valleys cross the brecks, draining westwards to the Cambridgeshire and Norfolk fens : the Wissey, Little Ouse and Lark, all tributaries to the River Ouse. Most of the collections of spiders referred to in this paper were taken on the heaths and fens of the Lark Valley, which is one of the most attractive and interesting areas in West Suffolk. Reclamation has made rapid progress in the Lark valley and only isolated relics are left of the fens which in the past must have been continuous with the marshes of the Fenland basin. T h e same applies to the Breck heaths which even thirty to forty years ago probably extended for many miles on either side of the river valley. T h e rapid rate at which these unique formations are disappearing makes the study of the natural history of the remaining sites of special importance and will also help to strengthen the case for preservation. Although there are many scattered references in the literature to the invertebrates of these places, there has been little effort to bring them together to illustrate the distinetive nature of the fauna. T h e spiders in particular have been little studied and the only contribution of note is the paper by Dr. W. S. Bristowe (1940). I n May, 1956, the three of us collected on several heaths and fens in the Lark valley area and on the Fenland margin, and this material together with other collections made by one of us (E.D.) during the period 1953 to 1957 forms the basis of the observations in this paper.
SPIDER FAUNA OF WEST SUFFOLK
Before discussing the collections made, brief descriptions are given below of the localities visited :â€” T H E F E N HABITATS 1. ICKLINGHAM POORS' F E N . A small fen bordering the north side of the River Lark situated between Icklingham Plains and Cavenham Poors' Heath. Much of it is usually very wet and dominated in part by large tussocks of Carex paniculata. There are also areas of reed and of Juncus subnodulosus. Collections were made in all three Vegetation typ es but particularly on the C. paniculata tussocks. Spiders were taken from the green Vegetation of the tussock crowns, from the dead leaves hanging down the sides and from the wet litter around the bases. 2.
TUDDENHAM F E N AND POOLS ON TUDDENHAM HEATH.
the south side of the River Lark the formerly extensive T u d d e n h a m Fen is now largely reclaimed. Spiders were collected from the tall Vegetation in the drains. On Tuddenham Heath are a number of shallow depressions (slacks) among the birch and pine. Some have permanent Standing water, others dry out in the summer. Spiders were collected in one dominated by C. paniculata tussocks which dries out some years. 3. LAKENHEATH POORS' F E N . Very little unreclaimed fen now remains in the interesting marginal country where the sandy breck heaths give way to the Fenland basin. One of the most interesting relics is the Turf of Poors' Fen just west of Lakenheath. This fen is grazed by cattle for part of the year and large areas are dominated by Salix repens and Cladium mariscus. There is a wealth of herbaceous fen plants, many of which are able to survive because their habitat is maintained by cattle grazing. This is offset, however, by a probable reduction in the zoological interest, and the occasional fires contribute further to this. Spiders were collected on the marginal Vegetation of the dykes, on the open fen and swept from the upper foliage of tall plants. T H E BRECK HEATHS 4. CAVENHAM HEATH. T h e National Nature Reserve which has been established in this area by the Nature Conservancy only Covers 132 acres at present, mostly heathland on the south side of the Lark by Temple Bridge. Nearly all the collections have been made in this area which includes birchwood, old heather heath, some sandsedge and a large area cultivated in the 1940's but now reverting to heather. Spiders were taken in the following :â€”
Leaf litter in tall dense Calluna. In the litter of a thick growth of sandsedge (Carex arenaria) and young heather.
SPIDER FAUNA OF WEST SUFFOLK
(iii) In birch leaf litter in the wooded area. (iv) By sweeping the foliage of tall heather. 5. TUDDENHAM HEATH. One of the most varied and interesting heaths in Suffolk. Collections in May, 1956 were made (i) by sweeping in a thick growth of sandsedge ; (ii) beating Scots pine foliage at 4-5 ft. 6. FOXHOLE HEATH. One of the finest remaining open brecks, situated on an upland slope, 2f miles north of the River Lark. Much of the northern slopes supports a very sparse jvegetation, mainly liehen and moss. Spiders were collected in this area and from gorse and broom foliage by beating at 3-4 ft. 7. ICKLINGHAM PLAINS AND ADJOINING HEATHS. The plains consist of open breck heath varying from areas of blown sand to thick sandsedge. Spiders were collected mainly in an area of bare sand andflintswith a sparse Vegetation of lichens, mosses and a few smallfloweringplants. Some speeimens were also taken by sweeping a sandsedge sward. Icklingham Plains, Foxhole Heath and Icklingham Poors' Fen were visited by kind permission of Lord Iveagh. THE SPIDERS OF THE FENS
A complete species list of the spiders taken in the fen localities will be found in Appendix I. A large proportion of the total of 71 species has a wide distribution in this country and no special attachment to fen and marsh habitats. About 37 species (52%) are either confined to wet places or are more common in such places than elsewhere. A small number are of very considerable interest and indicate a close affinity with the spiders of Wicken Fen, where many rare species may be found in numbers but were thought to be rare or absent elsewhere. Entelecara omissa is a fen species, reported as common at Wicken Fen but has been found in very few other localities. It was taken on Carex paniculata tussocks in Icklingham Poors' Fen. Lycosa rubrofasciata is a widespread and common lycosid at Wicken but there are very few other British Records. It was found, however, in all three fen habitats visited, Lakenheath Turf Fen, Icklingham Poors' Fen and Tuddenham Heath " Slacks ". Other rare or uncommon fen species recorded from Wicken Fen and the Lark Valley are Tibellus maritimus, Crustulina sticta, Pirat piscatorius, Theridion instabile, Linyphia impigra, Sitticu and Marpissa pomatia. Comparison with other fen areas shows some striking differences. Lycosa rubrofasciata is apparently absent from the extensive fens of the Norfolk Broads, the Suffolk coastal fens and also from the western side of the Fenland Basin at Wood Walton and Holme
SPIDER FAUNA OF WEST SUFFOLK
Fens. On the other hand, Marpissa pomatia, a large jumping spider, conspicuous on reed flowering heads in the summet, is common at Wicken Fen, in the Lark Valley and in all the Broadland river Valleys (excepting the Yare) but is absent from Wood Walton and Holme Fens and from the extensive reedswamps of the Suffolk coastal fens at Walberswick, Benacre, Covehithe and Minsmere. It is impossible to give an adequate explanation of this type of restricted distribution in the present State of our knowledge, but it seems likely that changing conditions of land use are an important contributory cause. At Wood Walton and Holme Fens reedswamp appears to have been local in distribution and no large areas survived after the drainage of Whittlesey Mere (the last Fenland mere) in 1852. Since that date reclamation has been rapid and the small areas which today have apparently never been cultivated have nevertheless been very extensively modified by repeated peat cutting. It is possible therefore that such species as Marpissa pomatia, if present in the Wood Walton and Holme Fens before reclamation, was only locally distributed and became extinct when its habitat was largely destroyedâ€”as did such birds as the Bearded Tit and other members of the fauna. T h e apparent absence of Marpissa pomatia, Lycosa rubrofasciata and other fen species from the large area of marsh and reedswamp of the East Suffolk coastal Broads is less easy to understand. Most of these marshes appear to have a history of reclamation to agriculture followed by neglect and reversion to nature, often brought about by a sea flood. T h e occurrence of these two events, destroying the habitat by drainage and reclamation and periodic flooding by the sea may have prevented establishment by susceptible fen species. T h e close similarity between the spiders of Wicken Fen and the Lark Valley is probably an indication of the former connection of the Fenland Basin fauna with that of the river Valleys draining into it. Drainage and reclamation have now confined these characteristic species groups to isolated islands of fen. THE
SPIDERS OF THE BRECK
A complete list of the spiders taken on the Breck will be found in Appendix I I . A total of 60 species was taken by us on May 26th and 27th, 1956. Approximately 17 of this total are typically associated with dry habitats and not often taken elsewhere, while most of the others are widespread in open grassy and heathery places away from water. Although the Breck and Fen collections were sometimes made on adj acent areas as at Icklingham Plains and Icklingham Poors'
SPIDER FAUNA OF WEST SUFFOLK
Fen, only 14 (10.6%) of the grand total of 131 species were taken in both places. Some comment on the structure of the two communities and their adaptations to the environment will help to emphasise their distinctive nature. Of the 11 Fen families and the 12 Breck families, three deserve special mention. Salticidae (Jumping Spiders) : two species were taken in the Lark Valley Fens and five on the Breck heaths. Typically this family is much better represented in species in tropical countries than in temperate regions. The hot and dry Mediterranean countries have a richer fauna, for instance, than this country. T h e same is true in many respects for the Theridiidae, 11 species being recorded for the Breck and five in the Fens. In many cases where the web is built on the ground, it appears best adapted to catching crawling types of prey such as ants and beetles. T h e largest family of British spiders is the Linyphiidae (about 250 species out of a total fauna of approximately 585 species in 24 families), most of which are small and only numerous where there is a thick growth of Vegetation or moist leaf litter. 11 species were taken in the Breck and 34 in the Fens. In the tall Fen Vegetation, there is a definite zonation of species as for instance on a Carex paniculata tussock. Some species are found in the moist " litter " lying on the ground surface, others spin their webs around the stem bases and others are found on the upper parts of the Vegetation. This zonation cannot develop on the Breck except in a very small way in tall sandsedge or in heather but in any case the dryness of the habitat appears unfavourable to most linyphiids. T h e recorded Breck spider fauna can be roughly divided into two categories :â€”â€˘ a. Species of wide distribution in this country but most frequent in open places such as downs, heaths, meadows, roadsides or similar situations. About two-thirds of the 60 species recorded on the Breck on May 26th/27th, 1956, can be described in this way. b.
Species more or less confined to dry sandy or stony places, local or rare, often southern in distribution. 17 species can be grouped under this heading (including Oxyptila scabricula taken on Weeting Heath and Scolt Head Island, Norfolk, in 1954 and 1955). All but four of these species which are adapted to life in arid places are hunting spiders, catching their prey by chase, jumping or a sudden snatch. Of the four web-spinners, three are Theridiids constructing a ground web, and the fourth is a very small orb-web Spinner. T h e 17 species do not include representatives of the Linyphiidae, the largest British family.
SPIDER FAUNA OF WEST SUFFOLK
7 of the 17 species are also well-known members of the fauna of coastal sand-dunes. Arctosa perita is a cryptically coloured lycosid particularly numerous on mobile dunes where there is a high proportion of open bare sand. On the older dunes where a complete Vegetation covering has developed, it is outnumbered by Lycosa monticola and a very similar Situation is found on the Breck heaths. Attulus saltator is a jumping spider found on sand-dunes, shingle and also on inland sandy heaths. Oxyptila scabricula is a rare crab-spider which has been taken on the Norfolk Breck at Weeting and on sanddunes at Scolt Head Island. A species of particular interest is Lithyphantes albomaculatus (:Theridiidae). This species was not known from Norfolk until recent years and was regarded as a rare spider of a few southern counties. On May 27th, 1956, we found it widespread on Foxhole Heath and Icklingham Plains, including numbers of adult males which were actively moving about. It has also been taken on other Suffolk and Norfolk inland heaths and in 1955 was recorded several times on shingle ridges adj acent to or crossing the saltmarsh of Scolt Head Island. The physical environment was very similar to the sand and flint formation on the breck heaths where it was found. The remaining 10 of the 17 dry heathland species have not been recorded on coastal dunes but may be frequent on inland localities. The most interesting of these was the discovery of Micaria silesiaca, an ant-mimic of the family Gnaphosidae. Numbers of these spiders were found running about on very barren Breck at Foxhole Heath where the Vegetation was mostly liehen and moss. They ran with great rapidity and were difficult to distinguish from the ants they mimicked. Previously this spider had been taken only from the New Forest and a heath near Woodbridge (Locket and Millidge, 1953). In late June of 1957, A.F.M. and E.D. took further speeimens on the sandy heathland near Walberswick. On the continent it has so far been recorded only from Germany, where it is said to occur on dry sandy places and in heather (Dahl, 1926). Other interesting inland heath species include Euophrys aequipes, a very tiny reddish-brown jumping spider ; Tarentula barbipes, a large and widespread lycosid found in many types of dry open habitat; Asagena phalerata, another Theridiid, having conspicuous markings and constructing a small ground web ; and Phrurolithus festivus, an ant-like spider of the family Clubionidae. This very brief preliminary investigation of Suffolk Fens and Breck spiders has shown that there are two very distinet faunas
SPIDER FAUNA OF WEST SUFFOLK
adapted to these environments. T h e presence or absence of moisture is obviously a very important factor, but equally significant is the Vegetation formation, particularly for the numerous web-spinning species. In the Fens the tall, dense plant growth provides a wide rĂ¤nge of microhabitats for web-spinners, while hunting spiders form a much higher proportion of the species found on the open formations of the Breck. These spiders are able to move over considerable areas in search of food and can also seek out the most suitable places for shelter and egg-laying in what must be a rigorous environment subject to extremes of temperature. T h e food supply must also be a limiting factor for small web-spinning linyphiids, which probably depend to a large extent on Collembola and other microarthropods in this size rĂ¤nge. These animals are frequent in moist places where there is an abundance of living and dead plant material, but may be very scarce on a dry Breck Heath. References W. S., 1940. T h e Arachnida of Suffolk. Trans. Suff. Nat., Vol. IV, pt. I I I . DAHL, F., 1926. Clubionidae. Die Tierwelt Deutschlands. Jena. LOCKET, G . H . and M I L L I D G E , A . F . , 1 9 5 3 . British Spiders, Vol. I I . Ray Society. BRISTOWE,
Spiders recorded from the Fen localities described in the foregoing account, unless otherwise stated. I.P.F.=Icklingham Poors' Fen T . F . = T u d d e n h a m Fen L . P . F . = L a k e n h e a t h Poors' * = C o n f i n e d to or most Fen frequently recorded T.H.S. = T u d d e n h a m Heath in wet habitats Slacks f = N e w county record (Bristowe, 1940) DICTYNIDAE
Dictyna arundinacea (L.) : I.P.F., L.P.F. \*Argenna subnigra (O. P.-Cambridge) : I.P.F., L.P.F. CLUBIONIDAE
*Clubiona reclusa (O. P.-Cambridge) : I.P.F. *C. stagnatilis (Kulczynski) : I.P.F., L.P.F. *C. phragmitis (C. L. Koch) : I.P.F., L.P.F. C. terrestris (Westring) : I.P.F. *C. lutescens (Westring) : I.P.F. (*) C. subtilis (L. K o c h ) : I.P.F., L.P.F. Zora spinimana (Sundevall) : I.P.F.
SPIDER FAUNA OF WEST SUFFOLK
Xysticus cristatus (Clerck) : L.P.F. *X. ulmi (Hahn) : I.P.F. •\*Oxyptila brevipes (Hahn) : I.P.F. *Tibellus maritimus (Menge) : L.P.F. SALTICIDAE
\*Marpissa pomatia (Walckenaer) : I.P.F., T.F. *Sitticus caricis (Westring): L.P.F. LYCOSIDAE
Lycosa pullata (Clerck): I.P.F. L. amentata (Clerck) : L.P.F. L. nigriceps (Thorell) : I.P.F., L.P.F. *L. rubrofasciata (Ohlert): I.P.F., L.P.F., T.H.S. f*Arctosa leopardus (Sundevall): L.P.F. *Pirata hygrophilus (Thorell) : I.P.F. *P. latitans (Blackwall) : T.H.S. f*P. piscatorius (Clerck): T.H.S. AGELENIDAE
•\Hahnia montana (Blackwall) : I.P.F. MIMETIDAE
Ero cambridgei (Kulczynski) : I.P.F. THERIDIIDAE
Crustulina guttata (Wider) : I.P.F. (*) C. sticta (O. P.-Cambridge) : I.P.F., L.P.F. \*Theridion instabile (O. P.-Cambridge) : I.P.F. T. bimaculatum (L.) : I.P.F. Pholcomma gibbum (Westring): I.P.F. TETRAGNATHIDAE
*Tetragnatha montana (Simon) : T.P.F. *Pachygnatha clercki (Sundevall) : I.P.F. ARGIOPIDEA
Araneus gibbosus (Walckenaer): L.P.F. (juvenile) *A. cornutus (Clerk) : L.P.F. A. redii (Scopoli): L.P.F. Singa pygmaea (Sundevall) : Cyclosa conica (Pallas): L.P.F. LINYPHIIDAE
*Cornicularia unicornis (O. P.-Cambridge): I.P.F., L.P.F. f*C. vigilax (Blackwall) : I.P.F. Dicymbium nigrum (Blackwall): I.P.F.
SPIDER FAUNA OF WEST SUFFOLK
f *Entelecara omissa (O. P.-Cambridge) : I.P.F., L.P.F. *Gnathonarium dentatum (Wider) : I.P.F., L.P.F. *Dismodicus bifrons (Blackwall) : I.P.F., L.P.F. *Hypomma bituberculatum (Wider) : I.P.F., L.P.F. •\*Minyrioloides trifons (O. P.-Cambridge) : I.P.F. Pocadicnemis pumila (Blackwall) : I.P.F., L.P.F. *Oedothorax gibbosus (Blackwall) : I.P.F., L.P.F. *Oe. tuberosus (Blackwall) : I.P.F., L.P.F. Cnephalocotes obscurus (Blackwall) : L.P.F. *Lophomma punctatum (Blackwall) : I.P.F. •\*Saloca diceros (O. P.-Cambridge) : I.P.F. \*Erigonella ignobilis (O. P.-Cambridge) : I.P.F. Diplocephalus picinus (Blackwall) : I.P.F. Erigone dentipalpis (Wider) : L.P.F. E. atra (Blackwall) : L.P.F. •\*Leptorhoptrum robustum (Westring) : L.P.F. •\Agyneta conigera (O. P.-Cambridge) : I.P.F. Microneta viaria (Blackwall) : I.P.F. •\Centromerus dilutus (O. P.-Cambridge) : I.P.F. f*Bathyphantes approximatus (O. P.-Cambridge): I.P.F. f ß . pullatus (O. P.-Cambridge) : I.P.F. B. gracilis (Blackwall) - I.P.F. Poeciloneta globosa (Wider) : I.P.F. *Taranuncus setosus (O. P.-Cambridge) : I.P.F. •\Lepthyphantes obscurus (Blackwall) : I.P.F. L. tenuis (Blackwall) : I.P.F. L. zimmermanni (Bertkau) : I.P.F. L. ericaeus (Blackwall) : I.P.F. Linyphia clathrata (Sundevall) : I.P.F. t L . pusilla (Sundevall) : I.P.F. f *L. impigra (O. P.-Cambridge) : I.P.F.
Spiders recorded from the Breck heaths described in the foregoing account, unless otherwise stated. I.P=Icklingham Plains F.H.=Foxhole Heath T.H. = T u d d e n h a m Heath C.H.=Cavenham Heath *=confined to or most frequently recorded from open dry habitats. f = n e w county record (Bristowe, 1940) DICTYNIDAE
Dictyna arundinacea (L.) : C.H. DYSDERIDAE
Dysdera crocata (C. L. Koch):
SPIDER FAUNA OF WEST SUFFOLK
Drassodes pubescens (Thoreil) : I.P. •\*Zelotes pedestris (C. L. Koch) : I.P. \*Micaria silesiaca (L. Koch) : F.H. CLUBIONIDAE
Clubiona compta (C. L. Koch) : C.H. C. diversa (O. P.-Cambridge) : L.P. (*) C. subtilis (C. L. Koch) : F.H. Cheiracanthium erraticum (Walckenaer) : F.H. Zora spinimana (Sundevall) : C.H. f *Phrurolithus festivus (C. L. Koch) : F.H. THOMISIDEA
Xysticus cristatus (Clerck) : F.H., C.H. X. audax (Schrank) : F.H. \X. kochi (Thoreil) : F.H. *X. erraticus (Blackwall): C.H. Philodromus aureolus (Clerck) : F.H. Tibellus oblongus (Walckenaer): C.H. *(Oxyptila scabricula (Westring): Weeting and Scolt Head, Norfolk, 1954 and 1955) SALTICIDAE
*Salticus cingulatus (Panzer) : F.H. Heliophanus ßavipes (C. L. Koch) : F.H. Euophrys frontalis (Walckenaer): C.H. f * E aequipes (O. P.-Cambridge) : F.H., I.P. \*Attulus saltator (Simon): F.H., C.H. LYCOSIDAE
•\*Lycosa agrestis (Westring) : F.H. *L. monticola (Clerck): I.P., F.H. L. pullata (Clerck): C.H. L. nigriceps (Thoreil) : C.H. •\Tarentula cuneata (Clerck) : I.P. *T. barbipes (Sundevall): F.H. f*Arctosa petita (Latreille): C.H. PISAURIDAE
Pisaura mirabilis (Clerck):
•\Episinus angulatus (Blackwall): C.H. (*) Crustulina sticta (O. P.-Cambridge): C.H. *Asagena phalerata (Panzer) : I.P., F.H. •\Lithyphantes albomaculatus (Degeer) : F.H., I.P. Theridion vittatum (C. L. Koch) : C.H. (immature)
SPIDER FAUNA OF WEST SUFFOI.K
T. T. T. T. T.
sisyphium (Clerck) : F.H. simile (C. L. Koch) : C.H. varians (Hahn) : C.H. tinctum (Walckenaer) : F.H. bimaculatum (L.) : C.H. (immature)
degeeri (Sundevall) : C.H.
Meta segmentata (Clerck) : C.H. Araneus gibbosus (Walckenaer) : F ' H . (juveniles) A. redii (Scopoli) : C.H. •fA. cucurbitinus opistographus (Kulczynski) : F.H., T . H . f*Singa albovittata (Westring) : I.P., F.H. S. pygmaea (Sundevall) : F.H., C.H., T . H . Cercidia prominens (Westring) : C.H. (immature) LINYPHIIDAE
•\Ceratinella brevipes (Westring) : C.H. •\Prosopotheca monoceros (Wider) : F.H. Gonatium rubens (Blackwall) : I.P. Peponocranium ludicrum (O. P.-Cambridge) : C.H., F.H. Cnephalocotes obscurus (Blackwall) : C.H. Microneta viaria (Blackwall) : C.H. Poeciloneta globosa (Wider) : F.H. \Lepthyphantes mengei (Kulczynski) : C.H. L. ericaeus (Blackwall) : C.H., I.P. Linyphia clathrata (Sundevall) : C.H. f l . pusilla (Sundevall): C.H. N.B. It has been well known for some time that certain species of spiders are commonly found both on sand dunes and in marshy places. No adequate explanation has yet been put forward but certain similarities of Vegetation form and possibly microclimate between fen Vegetation and marram tussocks may be important. Clubiona subtilis and Crustulina sticta (marked by (*) are examples in the above lists. On the Breck they were only taken in thick Vegetation, e.g. a sandsedge sward.
All matter for publication in the next issue of Transactions should reach the Editor, M R . G . E. CURTIS, BELSTEAD HOUSE, IPSWICH, b y I s t April, 1958.