Population Structure of Some Surface Dwelling Collembola in a Coniferous Forest Soil

The population structure of the surface dwelling Collembola Tomocerus minor (Lubbock), Lepidocyrtus cyaneus Tullberg, Orchesella cincta (Linne), Entomobrya nivalis (Linne), Isotomurus palustris (Muller) and Isotoma viridis Bourlet was studied between May 1963 and September 1964. 2. Temperature appeared to be an important cause in starting growth and reproduction in spring in all species. 3. Reproduction took place throughout spring, summer and autumn, the details being slightly different in the various species. In winter no reproduction occurred. 4. Lepidocyrtus cyaneus, Orchesella cincta, Entomobrya nivalis and Isotoma viridis appeared to have two generations per year. Tomocerus minor has three generations per year, made possible by its adaptation to lower temperature conditions. 5. After each egg-laying period a high adult mortality was obvious. 6. The species hibernated as half-grown individuals. The hibernating populations consisted of two generations. 7. During winter about half the populations of the six species died. This must be due to weathers factors, as predators were hardly active anymore. 8. On the basis of activity observations, it could be concluded that migration did not occur.