The terrestrial chapter of the Circumpolar Biodiversity Monitoring Programme (CBMP) has the potential to bring international multi-taxon, long-term monitoring together, but detailed fundamental species information for Arctic arthropods lags far behind that for vertebrates and plants. In this paper, we demonstrate this major challenge to the CBMP by focussing on spiders (Order: Araneae) as an example group. We collate available circumpolar data on the distribution of spiders and highlight the current monitoring opportunities and identify the key knowledge gaps to address before monitoring can become efficient. We found spider data to be more complete than data for other taxa, but still variable in quality and availability between Arctic regions, highlighting the need for greater international cooperation for baseline studies and data sharing. There is also a dearth of long-term datasets for spiders and other arthropod groups from which to assess status and trends of biodiversity. Therefore, baseline studies should be conducted at all monitoring stations and we make recommendations for the development of the CBMP in relation to terrestrial arthropods more generally.

The genus Psilochorus Simon, 1893 is reviewed for America north of Mexico. Nineteen species, five of which are new, are described, illustrated, mapped, and a key is provided for identification. Species included are: P. acantus Chamberlin and Ivie, 1942; P. apicalis Banks, 1921 (=P. gertschi Schenkel, 1950, new synonym); P. bantus Chamberlin and Ivie, 1942; P. californiae Chamberlin, 1919; P. coloradensis new species; P. concolor new species; P. hesperus Gertsch and Ivie, 1936; P. hooki new species; P. imitatus Gertsch and Mulaik, 1940; P. inyo new species; P. pallidulus Gertsch, 1935 (= P. coahuilanus Gertsch and Davis, 1937, new synonym); P. papago Gertsch and Davis, 1942; P. pullulus (Hentz, 1850); P. redemptus Gertsch and Mulaik, 1940; P. rockefelleri Gertsch, 1935; P. simoni (Berland, 1911) (= P. simplicior Chamberlin and Ivie, 1942, new synonym); P. topanga Chamberlin and Ivie, 1942; P. texanus new species; P. utahensis Chamberlin, 1919. Information on P. cornutus (Keyserling, 1887) is examined and the species is declared nomen dubium.

If the current rate of climate change continues, the composition, distribution, and relative population sizes of species in the higher latitudes of the Northern Hemisphere are likely to change considerably. Understanding the magnitude of this change requires a well-documented baseline against which to compare. Although specimen-less observations can help augment such a baseline for the minority of organisms that can be confidently identified in the field or from photographs, the vast majority of species are small-bodied invertebrates, primarily arthropods, that can only be identified from preserved specimens and (or) their tissues. Museum staff archive specimens and make them and their data available for research. This paper describes a number of challenges to the goal of thorough documentation of high-latitude arthropod biodiversity and their potential solutions. Examples are provided from ongoing and recently completed research that demonstrates the value of museum specimens and the sharing of their data via global portals like GBIF.org.Key words: Arctic, biodiversity, Arthropoda, monitoring, inventory, taxonomic bottleneck.Résumé : Si le taux actuel du changement climatique se maintient, la composition, la répar-tition et les tailles de population relatives d'espèces dans les latitudes plus hautes de l'hémi-sphère nord sont susceptibles de changer considérablement. Pour comprendre l'ampleur de ce changement, il faut une ligne de référence bien documentée contre laquelle on peut comparer. Bien que les observations sans spécimens puissent aider à augmenter une telle ligne de référence pour la minorité d'organismes qui peuvent être identifiés avec assurance sur le terrain ou à partir de photographies, la grande majorité d'espèces est composée d'inverté-brés à petit corps, principalement des arthropodes, qui ne peuvent être identifiés qu'à partir de spécimens préservés et (ou) de leurs tissus. Le personnel de musées archive les spécimens et les rend disponibles ainsi que les données connexes aux fins de recherche. Dans cet article, on décrit un certain nombre de défis à l'encontre du but de la documentation minutieuse de la biodiversité d'arthropodes à hautes latitudes et les solutions potentielles à ces défis. On fournit des exemples de recherche en cours et récemment complétée qui démontr-ent la valeur de spécimens de musée et le partage de données via des portails mondiaux comme le Système mondial d'informations sur la biodiversité (GBIF.org).

On 11 June 2008 the first author spent 10.66 h on Kasatochi Island and collected 396 terrestrial arthropod specimens estimated to represent a minimum of 58 species. Among these are included the first Alaskan records of the fly genus Lestremia and the ghost moth Sthenopis quadriguttatus (Grote). Also found were a new species of salpingid beetle in the genus Aegialites and sawfly in the genus Pseudodineura. On 10 and 12 August 2009, one year after an eruption that buried the island in ash, the first author spent 15 h sampling terrestrial arthropods. Specimens were also collected on 12-14 June 2009 by other team members. An estimated 17 post-eruption species were documented by the collection of 210 specimens. Evidence of breeding was seen in 4-9 species. Pitfall traps run from 14 June to 10 August 2009 flooded, capturing no arthropods. Fallout collectors representing 1 m 2 , run during the same period, had four flies and no seeds. The majority of species recovered post-eruption were probably survivors or their offspring, some of which had commenced breeding on rotting kelp and bird carcasses. Of significance as the first post-eruption evidence of multi-trophic level interaction, a fly predator on kelp flies, Scathophaga, and an ichneumonid endoparasite of flies, Phygadeuon, were also present. No phytophagous or fungivorous species were found. Supporting the heterotrophs-first hypothesis of Hodkinson et al. (2002), the current terrestrial ecosystem of Kasatochi is necromassbased rather than plant-based.

The spider Pacifiphantes magnificus (Chamberlin & Ivie 1943)(Linyphiidae), originally described as a member of the ge-nus Bathyphates, is redescribed and the first description of the male is presented. DNA barcoding was used to test the conspecificity of specimens from different collection events and to help match specimens from different sexes.