Spiders of Suffolk

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SPIDERS OF SUFFOLK W. A. THORNHILL The lack of attention which naturalists have given to most invertebrates, compared to birds and mammals for example, is particularly regrettable in the case of spiders because their varied life styles make them such fascinating creatures. Also, because the complex strueture of the adults' sexual organs are characteristic or the species, with the aid of a microscope identification is less of a problem than it is for many other groups of invertebrates. There are excellent identification guides both for the specialist (e.g. Locket & Millidge, 1951/3) and for the non-expert naturalist (e.g. Jones, 1983).

The wide Variation in life style stems largely from differences in the way spiders use silk. All spiders are predatory and all use silk, usually produced from spinnerets at the end of the abdomen, but not necessarily for building webs. They may use it to bind struggling prey, for constructing egg cases and retreats, and to facilitate movement through Vegetation. Unlike most adult insects they lack wings, but small spiders can disperse long distances through the air on Single threads of silk, mainly on still autumn days. Spiders also differ from insects in having four (not three) pairs of legs, and only two (not three) distinet parts of the body, owing to the fusion of the head and thorax into a cephalothorax.

The heaths, fens and coastal habitats of Suffolk have received the attention of several eminent arachnologists this Century (Bristowe, 1940: Duffey et al„ 1959), whereas habitats such as woodland, farmland and towns have been less thoroughly investigated. Occasionally, species lists for the county are published, most recently by Russell-Smith (1981), and new additions can still readily be found (Harvey, 1990). Currently, the list exceeds 300, and compnses 20 families.

The most spectacular addition to the species list was made by Duiiey (1958) of the Nature Conservancy who discovered Dolomedes plantarius, (family Pisauridae) generally known as the great raft spider, at Redgrave Fen on the border with Norfolk. The spiders are most likely to be seen at the edges of pools on warm summer days, although the two bold yellow or white stnpes, which most spiders possess, Camouflage them amongst the reed and sedge stems. Now that the water abstraction Station has been relocated the fen should stop drying out and deteriorating, and the spider may remain in the County. It still seems to be plentiful on the adjacent Lopham Fens, in Norfolk, very probably due to deep pools, some specially-dug, which permit open waler to be present even during droughts. Raft spiders catch prey amongst Vegetation or on the water surface. Like their common smaller relative, Pisaura mirabilis, they build a tent-like nursery web to protect the egg sac and spiderlings.

Wolf spiders (Lycosidae) are hunters, and an adaptation to this life style is that one pair of eyes is much larger than those of most other spiders. Several species, mainly Pardosa spp., can easily be seen in gardens and countryside as they scurry over the ground, the females often carrying greyish egg sacs below their abdomen. When the spiderlings hatch from their eggs they are carned around on the mother's abdomen for some days. Some uncommon species,

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such as Hygrolycosa rubrofasciata, a reddish species recorded from wct fenland sites, and Xerolycosa nemoralis, found on sandy heaths, are Suffolk residents.

Two large families of agile hunters well represented in Suffolk are the Gnaphosidae and Clubionidae. From the former, the nocturnal Zelotes spp. are sleek, predominantly black spiders. Micaria spp. are sun-loving and ant-like.

Clubonia (Clubionidae) is a large genus of small to medium-sized spiders, rather varied in appearance but all rather streamlined.

Jumping spiders (Salticidae) also have very large eyes to enable them to pounce accurately on their prey. The family includes some very attractive species. The familiar zebra spider, Salticus scenicus has black and white stripes on the abdomen. Marpissa pomatia is larger and rarer, and lives on fens, chiefly in the heads of common reed, Phragmites australis. An unusual jumping Spider, Myrmarachne formicaria, is recorded as a Suffolk species from a Single speeimen found at Redgrave Fen (Duffey, 1961). It resembles an ant in its appearance and movements.

The normal method by which crab spiders (Thomisidae) catch their prey is by lying-in-wait. The striking Misumena vatia is normally white or yellow, matching the colour of the flowerheads in which it rests, and individuals are able to change between these two forms. Thomisus onustus, an attractive purplish species, is found on heather. The ubiquitous Xysticus cristatus can occasionally be found on flowerheads, but tends to live on or close to the ground.

The spitting spider, Scytodes thoracica, the only British representative of the Scytotidae, is an interesting introduetion to our fauna and, being a native of warmer countries, only lives indoors here. It is a pale spindly spider which captures its prey by squirting sticky silk from its mouthparts. With its prey then restrained it moves in cautiously to deliver a poisonous bite.

The familiar long-legged house spiders, of the genus Tegenaria, family Agelenidae, are detested by many people. However, the abundant Agelena labyrinthica, of the same family, is lighter-|toloured and, though large, much less objectionable. It builds a similar large sheet web but lives outdoors amongst long grass, hedges etc.

The comb-footed spiders (Theridiidae) are mostly smallish, rather spindly species which build irregularly-shaped webs. Some Theridion species construct elaborate silken retreats above their webs, often largely from the remains of their victims. Episinus species construct a simple web which is sticky only near the ground, and hence is effective at catching ants and other small ground-dwelling insects.

Ero species, the sole representatives of the Mimetidae in the U.K., are predatory on other spiders. They are not powerfully- built, but their stealth and strong poison enables them to overcome spiders larger than themselves.

The Argiopidae, which are orb-web spinners, include some familiar species, such as Zygiella x-notata, commonly found in the corners of window frames, and some attractive ones. The ubiquitous garden spider, Araneus diadematus, may be black or brown and has a white cross on the abdomen. A marmoreus, found in woodland, may have similar markings, but more often

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has a cream abdomen with a dark brown pyramid-like marking (var. pyramidatus).

A quadratus is a large green or brown species found in grassland. Nucteana adiantum is a strikingly-marked heathland species, whereas the large N. sclopetarius is most commonly found by water. Meto, menardi is a large brown spider which lives in damp caves and cellars. The rarer M. bourneti, which lives in similar situations, was first recorded in the U.K. at Gedding, Suffolk.

The money spider family (Linyphiidae) is by far the best represented spider family in Suffolk (and in the U.K.), and comprises mainly small species. Most are piain, although the microscope reveals the males of some species to be bizarrely shaped. The head region may be grotesquely swollen, or, in another species, is extended into a long stalk, upon which are the eyes. Erigone males have laterally-protruding spines around the cephalothorax. Linyphiids are very numerous in most natural habitats and yet, of the majority of species, only the barest facts are known. Study of their life histories and ecology would soon yield interesting new information. Some rare species have been found on arable land in Suffolk (Thornhill, 1980).

Of the other arachnids, pseudoscorpions are predatory and use silk, though not for catching prey, harvest spiders are omnivorous and mites have a wide ränge of life styles. Several species of pseudoscorpions (Mendel, 1981) and harvest spiders, and many species of mites (Morley, 1940), provide fascinating material for the keen arachnologist to study in Suffolk.

References Bristowe, W. S. (1940). The Arachnida of Suffolk. Order Araneae: The true spiders. Trans. Suffolk Nat. Soc., 4: 156-165.

Duffey, E. (1958). Dolomedes plantarius. Transactions of the Norfolk and Norwich Naturalists' Society, 18: 1 - 5 .

Duffey, E. (1961). Spiders from Redgrave, Lopham and Hopton Fens in the Waveney valley. Trans. Suffolk Nat. Soc., 12: 31.

Duffey, E„ Locket, G. H. & Millidge, A. F. (1959). The spider fauna of the heaths and fens in West Suffolk. Trans. Suffolk Nat. Soc., 10: 199-209.

Harvey, P. R. (1990). A Survey at Sizewell, Suffolk. Newsl. Br. Arachnol. Soc., 57: 6.

Jones, R. E. (1983). Spiders of Britain and Northern Europe. Country Life.

Locket, G. H. and Millidge, A. F. (1951/3). British Spiders. Volumes 1 & II. Ray Society, London.

Mendel, H. (1981). A review of Suffolk Pseudoscorpions. Trans. Suffolk Nat. Soc., 18: 226-232.

Morley, C. (1940). The remaining Arachnida. Trans. Suffolk Nat. Soc., 4: 165-174.

Russell-Smith, A. (1981). The Spiders of Suffolk. Trans. Suffolk Nat. Soc., 18: 213-225.

Thornhill, W. A. (1980). The study of spiders and some recent records of interesting spiders found in Suffolk. Trans. Suffolk Nat. Soc., 18: 149-150.

W. A. Thornhill IARC-Broom's Barn, Higham, Bury St Edmunds, Suffolk IP28 6NP

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