Seasonal Tick Activity
All developmental stages of Ixodes ricinus hibernate under leaf litter in places where the temperature may be as low as 0°C (or, for short periods, even lower) and relative humidity amounts to at least 92%. Eggs and starved larvae perish at temperatures below –7°C.
Tick activity starts when the soil temperature rises to 5–7°C in March or April and ends late in the year when the average air temperature has declined to about the same value in October or November.
The seasonal peaks of tick activity depend on climatic factors. In Central Europe, a two-peak incidence curve has been observed for all developmental stages with maximum activities in May/June and September/October. In Northern Europe, and mountain regions, these two peaks converge into a single maximum in the summer months. ln the Mediterranean areas, maximum tick activity occurs between November and January.
Wet summers and mild winters tend to increase the tick population density. Warmer springs (March-May) might permit an earlier onset of questing activity, while raised temperatures throughout the spring-autumn period (March-September) would accelerate inter-stadial development.
Female ticks feeding in spring start to deposit eggs in early July. The larvae hatch in the same year, but mostly find their host in the following spring. Larvae and nymphs feeding in spring or early summer undergo metamorphosis and, in the same year, appear as the next stage of development. The activity of the larvae of Ixodes ricinus usually starts one month later than that of nymphs and adults.