none2003 Results from an extensive insect and arachnid inventory of the Romelson Island in the Vasterbotten Province of north Sweden are presented. The island is 4,5 km long and is diverse in both aquatic and terrestrial habitats. Aquatic habitats were covered throughout the island while on land the focus was on the southern part consisting of a sand-dune area and an old-growth open pine forest. Methods used include malaisetraps, trunk windowtraps, yellow pans, and handnets. The inventory covers a wide taxonomic range with special effort in sampling aculeate wasps, saproxylic ichneumonids, lacewings (Neuroptera), hoverflies (Syrphidae), lower Diptera ("Brachycera"), aquatic and woodliving Coleoptera, aquatic Heteroptera, macrolepidoptera and groundliving spiders (i.e. Lycosidae). In total we report 442 species of insects and arachnids including: 52 spiders, 106 terrestrial and 61 aquatic Coleoptera, 85 aculeate wasps, 47 hoverflies, 17 other Diptera, 28 macrolepidoptera, 17 lacewings, and 16 Heteroptera. Neoxorides montanus (Hymenoptera: Ichneumonidae: Poemeniinae) is new to the fauna of Sweden, and approximately 40 species are new regional records to Vasterbotten (1 Chrysopidae, 1 Coniopterygidae, 3 Syrphidae, 5 brachyceran Diptera, 4 saproxylic lchneumonidae, 1 Sphecidae, 1 Apidae: Megachilinae, 1 Staphylinidae, 1 Melyridae, 1 Pseudoscorpiones: Chernetidae, and ca 21 spiders, Araneae). Species redlisted in Sweden include the beetles Nothorina punctata VU, Mycetochara obscura NT, Abdera flexuosa NT, Atheta pandionis NT, Enicmus planipennis NT, the sphecid wasps Ammophila campestris NT and Crossocerus lundbladi NT, and the spider Dictyna major DD. Thi population of the vulnerable Nothorina punctata, developing in very old, sunexposed living pine trunks with rough cortex, was extraordinarily vivid based on both the distinct traces on suitable tree trunks and on the finding of one of its ichneumonid parasitoids Xorides depresses. Two N. punctata specimens were also recovered in the trunk windowtraps, an important proof that the traces were not only historical. The finding of Chrysopa dorsalis is by far the northern most record of this Eurasian lacewing species and several more species herein reported are the northernmost records from Sweden. We conclude that the conservation value of the sand-dune area and accompanying old-growth pine forest of southern Romelson is high based on the insect and spider fauna and reserve status is warranted. Conservation; Habitat; Terrestrial habitat; Land zones; Palaearctic region; Eurasia; Europe Arachnida; Insecta; Endangered status; Annotated list of records significance; Island habitat; Sweden; Vasterbotten; Romelson Island; Annotated list of recorded species including new records & endangered species