Invertebrate survey at Gunpowder Park, the former Royal Ordnance Site in the Lee Valley Appendix 1 National status explanation Nationally Rare species arc those falling within the Status categories defined in the British Red Data Books (Bratton. 1991; Shirt, 1987). These are internationally recognised species listed in the various Red Data Books published by or under the auspices of, the International Union for the Conservation of Nature (IUCN). Species included may not be informally removed or transferred between categories. There are four main categories; RDB 1 (Endangered) species are taxa in danger of extinction and whose survival is unlikely if the causal factors continue operating. These include: species known from only a single locality since 1970; species restricted to habitats which arc especially vulnerable; species which have shown a rapid and continuous decline in the last twenty years and are now estimated to exist in five or fewer localities; species believed extinct but which would need protection if re-discovered. RDB 2 (Vulnerable) species are taxa believed likely to move into the Endangered category in the near future if the causal factors continue operating. These factors include: species declining throughout their range; species in vulnerable habitats; species whose populations are low. RDB 3 (Rare) species are taxa with small populations, which are not at present endangered or vulnerable but that are at risk. These include species that are estimated to occur in fifteen or fewer localities. RDB K (Insufficiently Known) species arc taxa suspected to fall within the RDB categories but which are at present insufficiently known to enable placement. A review of statuses is taking place using new IUCN criteria, but this has not yet been applied to the majority of invertebrate groups. A national spider review is currently in progress. Nationally Scarce species are those falling within the Nationally Notable categories introduced by Ball (1986). They are species that are estimated to occur within the range of 16 to 100 ten-kilometre squares of the British National Grid system since 1970. These have subsequently been revised for a number of taxa; those affected in the results for the Royal Ordnance site are Araneae (spiders), revised by Merrett (1990), aculeate Hymenoptera, revised by Falk (1991a), Coleoptera, revised by Hyman & Parsons (1992, 1994), Diptera, revised by Falk (1991b) and Hemiptera revised by Kirby (1992). Nationally Notable species are subdivided as follows: Na (Notable A) species estimated to occur within the range of 16 to 30 10-kilometre squares of the National Grid System. Nb (Notable B) species estimated to occur within the range 31 to 100 10-kilometre squares of the National Grid System. N (Notable) Diptera (flics) and some Coleoptera (beetles) arc not separated, falling into either category Na or Nb. Nationally Local species are those that do not qualify as Nationally Notable but are less widespread and restricted than species considered common. Remaining species are either considered 'Common7 or, where insufficient information is available, 'Unknown'. These designations have been obtained from the JNCC Recorder 3 software. Regional (Essex) status explanation Essex Red Data species are those included in the provisional Essex Red Data list produced by the Field Club's County Recorders and other Essex naturalists on behalf of English Nature. The list is currently available at www.essexfieldclub.org.uk. At present some taxonomic groups remain to be done, and Diptera (flics) is incomplete, covering only those taxonomic groups covered by Falk's 1991 status review (Falk 1991b). The remaining Diptera families are awaiting the availability of forthcoming national status reviews. I 14 Essex Naturalist (New Series) 21 (2004)