Seasonal Activity of Lumbricids in Southern Sweden

Population densities and development throughout the year of different lumbricid species were estimated by handsorting, and compared with formaldehyde catches in order to estimate percentage of active individuals. Activity (= excitability, trappability) was defined as the number of individuals obtained by formaldehyde as a percentage of the actual population. The study showed that lumbricid activity was seasonal. All species were more or less inactive during winter, while reduced activity or inactivity during summer was exclusively found in Allolobophora. Dendrobaena and Lumbricus were active at 0-20?C when soil moisture was below pF 4.2. Allolobophora showed low activity below 2-4?C, and above 14-16?C when pF > 3.2-3.5. Differences in activity were seen between juvenile and adult Allolobophora and Lumbricus. Factors other than soil microclimate, e.g. food, are suggested to be important in the regulation of lumbricid activity.