-Pitfall trapping is probably the most frequently used method for sampling grounddwelling arthropods. While the capture of specimens in pitfall traps largely depends on the number of individuals in the sampled area, trap design and trapping effort for a given environment, can also affect sampling success. The aim of this study was to determine the best pitfall trapping design for collecting ground-dwelling arthropods in the wind-blown and cold arid steppe areas of Patagonia. We tested four designs of traps, six types of preservative and different times of activation as well as the quantity of traps. Both preservation attributes and sampling effi ciency differed between different trap designs and fl uids compared. We conclude that in order to obtain reliable data on the structure of a community of ground-dwelling arthropods in Patagonia, at least three pitfall traps per experimental unit are required. In addition, traps should be opened for a minimum of 10 days fi lled with 300 ml of 30% ethylene glycol. We also suggested the use of a simple trap design (i.e. without funnel or roof). We believe these fi ndings will contribute to more appropriate sampling of the ground dwelling fauna of Patagonia as well as other arid areas, leading to more reliable diversity studies.

Resumen. Se realizó un estudio sobre los patrones biogeográficos de los tenebriónidos epigeos (Coleoptera: Tenebrionidae) que habitan el Área Natural Protegida Península Valdés (Chubut, Argentina), basado en datos de colecciones y material recolectado en viajes a la zona. Se presenta una lista exhaustiva de las especies en la que se consigna el grado de adaptación a la aridez de cada una de ellas; un análisis de la calidad del inventario y la estimación de la riqueza total de especies; una evaluación de los patrones de distribución y riqueza, y la identificación de áreas de significativa mayor riqueza o hotspots. Los resultados indicaron que 25 especies con diferente grado de adaptación a la aridez habitan la península, aunque se estima que la riqueza total del área debería ser de 27. Además, se reconoció que los rangos de distribución de los tenebriónidos siguen una distribución log-normal y que sólo 3 especies son endémicas. Espacialmente, la riqueza se distribuyó de forma agregada en la península y se determinaron 10 hotspots. Finalmente, considerando que en la península Valdés están permitidas actividades productivas que originan una importante degradación del hábitat, se examina la implicancia de los resultados para la conservación de los tenebriónidos epigeos. Palabras clave: lista de especies, adaptaciones a la aridez, endemismos, riqueza de especies, efecto península, efecto del dominio medio, degradación de hábitat, áreas prioritarias de conservación.

Three new taxa from Peninsula Valdés (Argentina) are described for the tribe Praociini (Pimeliinae): Calymmophorus peninsularis sp. nov. and two subspecies of Praocis (Hemipraocis) sellata Berg 1889: P. (H.) sellata peninsularis ssp. nov. and P. (H.) sellata granulipennis ssp. nov. The first two taxa are endemic to the peninsula and the third one is distributed in and outside the peninsula. Distribution maps, habitat records and habitus photographs for these three new taxa are included, with comparisons to other known species of the genera. An identification key to the five subspecies of Praocis (Hemipraocis) sellata is provided. A discussion is presented on endemicity and sympatry of two species of Calymmophorus Solier 1840, and non-sympatry of two subspecies of Praocis (Hemipraocis) sellata. The following synonymy is reported and illustrated: Praocis sellata bruchi Kulzer 1958 = Praocis sellata topali Kaszab 1964 syn. nov.

Regionalization in biogeography allows division of the globe into areas according to different criteria, such as combination of biotic elements, physiognomy and climate. This regionalization constitutes a hierarchical system which comprises many categories of areas, from realms to biogeographic districts

Plant water stress can affect selectivity by insect herbivores. Numerous studies have shown greater insect preference for water-stressed plants, but others have reported the opposite response. We evaluated leaf consumption by adults of Nyctelia circumundata (a chewing insect) in leaves of Larrea divaricata and Prosopis alpataco. Three bioassays (two-way choice tests) were performed: two intra-specific comparisons between wellwatered (?W) and water-stressed (-W) leaves of each species and one inter-specific comparison between leaves of the two species. Leaf biomass was reduced by water stress in both species. Nitrogen concentration in leaves (N) was reduced by drought in P. alpataco. In contrast, total phenolics and specific leaf area (SLA) did not differ between treatments within species. Nyctelia circumundata did not show preference by any water supply regimes in intra-specific comparisons. In contrast, in inter-specific choice tests, it showed a marked preference for P. alpataco, which is the species with the highest nitrogen concentration and lowest total phenolics concentration. In intra-specific comparisons, maximum leaf consumption was inversely related to SLA in both species. Furthermore, in P. alpataco, N concentration was positively related to maximum leaf consumption and negatively related to leaf water content (LWC). In contrast, in inter-specific comparisons, total phenolics was negatively related to maximum leaf consumption, while N concentration exhibited the opposite trend. These results suggest that food selection is a hierarchical process where chemical attributes (i.e., total phenolics and N) are taken into account for species selection, and physical attributes (i.e., SLA and LWC) for choosing individuals inside species.