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Tetramorium Mayr, 1855 is a worldwide distributed and hyperdiverse ant genus consisting of almost 600 taxa manifesting various life history strategies. Species of the Tetramorium inquilinum species-group represents one of the most extreme forms of parasitism and consist of degenerate workerless social parasites of several Tetramorium species. So far, its members have been recorded in the Palearctic from montane to alpine zones and reveal an interesting disjunction in host selection observed between eastern-Mediterranean and western-Mediterranean species. We describe a fifth member of the Tetramorium inquilinum species-group: Tetramorium albenae Salata, van Delft & Borowiec sp. n. The species morphologically differs from the remaining members of the group by the combination of the following characters: dense and erect pilosity of appendages and the whole body, smooth head sculpture, predominantly smooth anepisternum and katepisternum, lack of blunt teeth on propodeum, and presence of distinct carianae on the dorsolateral margins of the propodeum. Tetramorium albenae Salata, van Delft & Borowiec sp. n. was collected in a lowland olive grove, a site so far not associated with the Tetramorium inquilinum species-group, from a nest of Tetramorium kephalosi (a new host species for the group). The data presented in this paper provide new insights into the habitat preferences of the species of the Tetramorium inquilinum species-group and extend our knowledge on the potential host species of these parasites. [ABSTRACT FROM AUTHOR]

Arthropods play an essential role in steppe ecosystems. However, studies testing the overall response of terrestrial arthropods to overgrazing are scarce. The problem is particularly worrisome in Central Asia, while, to date, only a very few broader studies have been conducted in this region. We investigated how epigeic terrestrial arthropod assemblages respond to different livestock grazing pressure in two ecozones in SE Mongolia by examining their structure using pitfall traps. We also assessed which groups can be utilised as the most efficient indicators of grazing intensity. Our analyses demonstrated that the habitat type, grazing intensity, and the interaction of these variables had a significant effect on the overall species composition and abundance. However, the grazing intensity caused different changes in the composition of arthropod communities in both studied ecozones. Contrary to the semi-desert, in the steppe habitat, the grazing had the strongest impact in the moderately grazed site. It is most likely because steppe-dwelling species are more sensitive to loss of plant biomass and changes in habitat structure. We also found that the most representative species within and from different groups can react differently to changing grazing intensities, indicating with their presence the characteristics of the respective habitat. Such differences should also be considered when elaborating the management plan of conserved species but also when applying grazing management in different habitat types. Our survey is one of the most comprehensive in Central Asia and should help implement further, more targeted studies in the corresponding habitats. In meadow steppes and other arid habitats, livestock grazing is one of the most severe causes of desertification and leads to an overall decline in vegetation cover, plant species richness and aboveground biomass, and, consequently, most often negatively affects arthropod diversity. Although the impact of grazing on arthropod diversity has already been the subject of numerous studies, most of them were focused only on a single or small number of arthropods and were conducted outside Central Asia (e.g., there is only one paper dealing with analyses of several arthropod groups conducted in Mongolia, where over 40% of the human population depends on pastoral livestock production and up to 90% of its territory belongs to various arid areas). We hypothesise that the overall diversity of different arthropod groups will change according to the grazing intensities, and these changes will depend on the habitat type and will differ between arthropod groups. Our analyses demonstrated that the habitat type, grazing intensity, and the interaction of these two variables significantly impacted the overall species composition and abundance. Our results highlight that the different terrestrial arthropod groups and representative species of the most abundant groups can react differently to changes in grazing intensity, and such differences should be considered when elaborating the management plan of conserved species and when applying grazing management in different habitat types. Our results also highlight that the species diversity alone cannot indicate the changes in species composition along the grazing intensity, and one should also consider the individual needs of specific species while investigating the impact of grazing on arid habitats. [ABSTRACT FROM AUTHOR]

We consider the motion of the image of a distant radiation source microlensed by one and many point masses in the presence of an external background field, which produces a shear in the lens equation. The trajectories of the image brightness centroid (BC) in a Chang-Refsdal lens are very sensitive to the magnitude of the shear and to the direction of motion of the microlenses, allowing these parameters to be unambiguously determined from the BC motion. Stochastic motions of the BC for an extended source are simulated in a problem with a large number of randomly arranged microlenses. We derive dependences of the root-mean-square variations in BC velocity on microlense density, on external shear, and on the continuous component of the mass density, which may be related to dark matter in extragalactic lenses. © 2001 MAIK “Nauka / Interperiodica”. [ABSTRACT FROM AUTHOR]

ABSTRACT Since September 1994 the GRANAT satellite has been almost continuously operated in the scanning mode, spinning with a period of 12 minutes around an axis pointed roughly at Sun. The SIGMA soft gamma ray telescope, having its main axis perpendicular to the spin axis, has been accumulating photons in four broad energy bands (40-600 keV) every 4 seconds. In this paper we present a method of the satellite attitude reconstruction in case of presence of at least one strong point source in the field of view. This method makes extensive use of the knowledge of the angular response of the SIGMA telescope both in the precise timing analysis and in the determination of the spin axis orientation. We discuss in detail the accuracy of our approach. [ABSTRACT FROM AUTHOR]