SPIDERS OF RAF MILDENHALL
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THE SPIDERS OF RAF MILDENHALL PAUL LEE Land utilised by the military for several decades or more may support areas of relict habitat which have been lost from the surrounding countryside through agricultural and development pressures. In this way, fragments of semi-natural breckland, which may otherwise have been ploughed up or disappeared under concrete, have been preserved through the establishment of air bases on the Suffolk Brecks during the 1920s. At RAF Lakenheath the value of this habitat is recognised by the designation of the airfield as a Site of Special Scientific Interest. Although there has been little work on the invertebrates of the SSSI, the results of a survey by English Nature suggest the fauna may be very rich (Key, Drake, Sheppard & Procter, 1992). At RAF Mildenhall similar habitats exist but the airfield is not a SSSI and is better known for air shows than natural history. However, recent work suggests that the invertebrate fauna is at least as diverse as that of RAF Lakenheath and includes a number of nationally important species (Lee & Suffolk Moth Group, 1999). In this paper the arachnological component of this invertebrate fauna is discussed and compared with that from other sites in Suffolk. Survey methods At the end of 1998 I was contracted by SWT Trading Ltd to undertake a preliminary survey of a number of invertebrate groups, including spiders, on the USAF base at RAF Mildenhall. This was followed by a more complete survey of the site between May and November 1999. As a result of the preliminary survey six sites were selected for detailed investigation in 1999. Habitat descriptions and grid references for these sites are given in Table 1. At each location a line of five pitfall traps was set in May 1999 (July in site 6) and emptied at monthly intervals until November. These habitats and a number of others around the air base were also sampled using hand-collecting techniques, sweep netting and / or beating as appropriate and vacuum samples were taken from areas of relatively short grassland on days in July, August and September when the vegetation was sufficiently dry.
Table 1. Details of main sites surveyed during 1999 Site 1 2 3 4 5
Grid Reference TL678771 TL711765 TL695759 TL679774 TL677772
6
TL700760
Site Description Calcareous grassland at west end of airfield Calcareous grassland at east end of airfield Ruderal vegetation and bare ground in waste disposal area Coniferous plantation Narrow fringe of grassland and scrub along south western edge of coniferous plantation Hawthorn scrub and ruderal vegetation
Trans. Suffolk Nat. Soc. 36 (2000)