Seasonal occurrence of Ixodes ricinus (Acari) in vegetation and on small mammals in southern Sweden

Seasonal activity of Ixodes ricinus L. was studied with two different sampling methods at three localities in southern Sweden: blanket dragging in vegetation and collection from small mammal hosts (mainly larvae in the latter case). The blanket method yielded all development stages. The seasonal pattern ‐ bimodal, with one peak in spring and another in autumn – was clearer for larvae collected on small mammals. The nymphs had a similar seasonal activity pattern as the larvae, but nymphal activity usually started somewhat earlier in spring. Adults had three activity peaks – spring, summer and autumn – in the vegetation. The autumn peak seems similar to that found in other European countries, but the timing of the spring peak differs. Weather, influencing development rates, seems to be the main agent behind these differences, since ambient weather (above a certain threshold) cannot explain the patterns. Abundance and activity of hosts (different hosts for different developmental stages) probably also plays a certain role.