[Diurnal rhythm in salamanders]

1. The locomotor activity of European salamanders differs from species to species. At all stages of development Triturus vulgaris is more light-active, Salamandra salamandra is dark-active, while Triturus alpestris and cristatus occupy an intermediate position. 2. The activity of the larvae is high but the rhythm is not very pronounced. Triturus larvae are less dark-active than adults (Fig. 2). 3. Periodism disappears completely during metamorphosis but after some weeks of terrestrial life a diurnal rhythm reappears (Fig. 3). 4. Adults of Triturus species show an increased activity during their aquatic life in spring: they are active by day and night, maxima occurring in twilight or darkness. 5. Terrestrial adults leave their hiding places only during twilight or darkness. Triturus vulgaris and alpestris display locomotor activity in twilight only whereas Triturus cristatus and Salamandra salamandra are also active in the dark (Figs. 5, 6).