The causes of the tremble dance of the honeybee,Apis mellifera

Tremble dances are sometimes performed by returning forager bees instead of waggle dances. Recent studies by Seeley (1992) and Kirchner (1993) have revealed that this behaviour is part of the recruitment communication system of bees. The ultimate cause of tremble dances is, according to Seeley (1992), an imbalance between the nectar intake rate and the nectar processing capacity of the colony. This imbalance is correlated with a long initial search time of returning foragers to find bees to unload them. However, it remained unclear whether a long search time is the direct proximate cause of tremble dancing. Here we report that a variety of experimental conditions can elicit tremble dances. All of them have in common that the total search time that foragers spend searching for unloaders, until they are fully unloaded, is prolonged. This finding supports and extends the hypothesis that a long search time is the proximate cause of tremble dancing. The results also confirm the previous reports of Lindauer (1948) and others about factors eliciting tremble dancing.     

Acoustical signals in the dance language of the giant honeybee,Apis dorsata

Summary Acoustical signals emitted by dancing bees have recently been shown to transmit information about the location of food sources in the western honeybee, Apis mellifera. Towne (1985) reported that in the Asian honeybee species Apis dorsata, which builds a single comb in the open under overhanging rocks or tree branches, sound signals were not emitted by the dancers. This led to the conclusion that acoustical communication is restricted to bees that nest in the dark, like A. mellifera. Here we show that in fact A. dorsata produces dance sounds similar to those emitted by A. mellifera, and that these acoustical signals contain information about distance, direction and profitability of food sources. The acoustical transfer of information has thus evolved independently of nesting in dark cavities. The significance of nocturnal activity in Apis dorsata for the evolution of sound communication is discussed. Correspondence to: W.H. Kirchner     

Images of the invisible-prospection methods for the documentation of threatened archaeological sites

To understand the development of prehistoric cultural and economic activities, archaeologists try to obtain as much relevant information as possible. For this purpose, large numbers of similar sites must be identified, usually by non-destructive prospection methods such as aerial photography and geophysical prospection. Aerial archaeology is most effective in locating sites and the use of digital photogrammetry provides maps with high accuracy. For geophysical prospection mainly geomagnetic and geoelectrical methods or the ground-penetrating radar method are used. Near-surface measurements of the respective contrasts within physical properties of the archaeological structures and the surrounding material allows detailed mapping of the inner structures of the sites investigated. Applying specially developed wheeled instrumentation, high-resolution magnetic surveys can be carried out in a standard raster of 0.125Ǵ.5 m covering up to 5 ha per day. Measurements of ground resistivity or radar surveys in a raster of 0.5 or 0.5Ǵ.05 m, respectively, are used to gain information on archaeological structures and on the main stratigraphic sequence of sites covering up to 0.5 ha per day. Data on intensities of the Earth's magnetic field, apparent resistivities of the ground or amplitudinal information of radar reflections are processed using a digital image processing technique to visualize the otherwise invisible archaeological structures or monuments buried in the ground. Archaeological interpretation, in the sense of detecting, mapping and describing the archaeological structures, is done using GIS technology by combining all relevant prospection data. As most of the Middle European archaeological heritage is under a massive threat of destruction, dramatically accelerated by intensive agriculture or industrial transformation of the landscape, the prospection techniques presented here represent an approach towards an efficient documentation of the disappearing remains of our ancestors.     

Die Titicaca-See-Region auf dem Altiplano von Peru und Bolivien und die Folgen eingeführter Fische für Wildarten und ihren Lebensraum

In the course of a long-term case study (since 1960) the interaction between different exotic fish (salmonids, atherinids) on the endemic ichthyofauna (genusOrestias: Cyprinodontidae) introduced to the interandean basin of Lake Titicaca was observed. The contribution deals not only with the actual consequences which endanger endemic species but also the socio-economic effects on the native Indian population, both causing further ecological problems in the region of concern.