Braided gravel-bed rivers are widespread in temperate piedmont and mountain-valley areas. In their pristine state, braided rivers are characterized by a shifting mosaic of channels, ponds, bars, and islands, since both flow and flood pulses create a diversity of habitats with fast turnover rates. Large wood has a major role in determining the geomorphology and ecological functioning of these rivers. Braided river habitats are colonized by a diverse fauna and flora adapted to their dynamic nature, including a significant proportion of highly endangered species. Animals exhibit high mobility, short and asynchronic life cycles, and ethological and phenological plasticity. Braided gravelbed rivers also offer various categories of refugia such as shore areas, hypogeic and hyporheic habitats that are pivotal for maintaining diversity in the face of frequent disturbances. Today, however, most gravel-bed rivers bear little resemblance to their highly dynamic natural state due to anthropogenic modifications, and most braided rivers have been converted into incised single-thread channels. Gravel bars and vegetated islands are among the most endangered landscape elements worldwide. They are very sensitive to channelization, gravel extraction, and flow regulation. Therefore, more than for most other ecosystems, restoring braided rivers and their landscape elements means restoring their underlying hydrogeomorphological dynamics.

The microdistribution of five butterfly species through their flying season was analyzed in a mosaic‐like habitat, brought about by secondary succession In order to explain the patterns observed, activity patterns and the use and distribution of nectar sources were determined Emphasis was laid on the changing allocation of visits to flower species and changing abundances of flowers during the season The use of nectar sources was basically limited to three flower species, Centaurea scabiosa, C bracteata and Serratula tinctoria As a consequence, niche breadth values were generally low and niche overlaps generally high Some butterflies changed their patterns of flower visits during the season and therefore reduced niche overlap with the other butterfly species The microdistribution of Melanargia galathea, Lysandra condon, Ochlodes venatus and Lictoria achilleae was strongly influenced by the distribution of their preferred nectar sources as well as by areas generally rich in flowers Changing flower preferences of Melanargia galathea and Lysandra coridon males during the course of the season were also expressed by changes in the correlations between the distribution of these butterflies and their nectar plants The distribution of nectar sources was not found to be of importance for Coenonympha arcanta, a species which rarely visited flowers

The snow flea Ceratophysella sigillata, a winter-active species of springtail, produces unique polychlorinated octahydroisocoumarins to repel predators. The structure of the major compound, sigillin A, was elucidated through isolation, spectroscopic analysis, and X-ray crystallography. Sigillin A showed high repellent activity in a bioassay with predatory ants. A promising approach for the total synthesis of members of this new class of natural compounds was also developed.

1. Individual supercooling points ranged from -2 t o -44" C for six species of springtails, five species from the Swiss Alps and one from lowland Britain. Individuals of Isotomuncs alticola (Carl) and Isotoma vindis Bourlet without gut contents had substantially lower supercooling points than those containing food material. 2.Juveniles were more cold resistant than adults in both Lalticola and Isotoma hiemalis Schott, both with respect to supercooling point and to their survival at prolonged subzero temperatures.3. Temperature and acclimation time affected the degree of supercooling of four of the Alpine species especially I.hiemalis.4. Duration of culture period had no consistent influence on the supercooling potential of all the species. 5. Tests for glycerol in the body fluids of the five Alpine springtails were negative, but the presence of a sugar, probably glucose, together with a five carbon polyhydric alcohol was indicated by chromatography.

Abstract. Ceratophysella sigillata (Collembola, Hypogastruridae) has a life cycle which may extend for >2 years in a temperate cli mate. It exists in two main morphs, a winter-active morph and a summer-dormant morph in central European forests. The winteractive morph often occurs in large aggregations, wandering on leaf litter and snow surfaces and climbing on tree trunks. The summer-dormant morph is found in the upper soil layers of the forest floor. The cryobiology of the two morphs, sampled from a population near Bern in Switzerland, was examined using Differential Scanning Calorimetry to elucidate the roles of body water and the cold tolerance of individual springtails. Mean (SD) live weights were 62 ± 16 and 17 ± 6 pg for winter and summer individuals, respectively. Winter-active springtails, which were two feeding instars older than summer-dormant individuals, were significantly heavier (by up to 4 times), but contained less water (48% of fresh weight [or 0.9 g g-1 dry weight]) compared with summer-dormant animals (70% of fresh weight [or 2.5 g g-1 dry weight]). Summer-dormant animals had a slightly greater supercooling capacity (mean (SD) -16 ± 6°C) compared with winter-active individuals (-12 ± 3°C), and they also contained significantly larger amounts of both total body water and osmotically inactive (unfrozen) water. In the summer morph, the unfrozen fraction was 26%, compared to 11% in the winter morph. The ratio of osmotically inactive to osmotically active (freezable) water was 1:1.7 (summer) and 1 : 3.3 (win ter); thus unfrozen water constituted 59% of the total body water during summer compared with only 30% in winter. Small, but sig nificant, levels of thermal hysteresis were detected in the winter-active morph (0.15°C) and in summer-dormant forms (0.05°C), which would not confer protection from freezing. However, the presence of antifreeze proteins may prevent ice crystal growth when feeding on algae with associated ice crystals during winter. It is hypothesised that in summer animals a small decrease in freezable water results in a large increase in haemolymph osmolality, thereby reducing the vapour pressure gradient between the springtail and the surrounding air. A similar decrease in freezable water in winter animals will not have such a large effect. The transfer of free water into the osmotically inactive state is a possible mechanism for increasing drought survival in the summer-dormant morph. The ecophysiological differences between the summer and winter forms of C. sigillata are discussed in relation to its population ecology and survival.