Figure 2

Stylised I. ricinus seasonal questing activity (based on data collected in the Neuchâtel area, Switzerland). In Switzerland, questing ticks may be collected as early as mid-February to early March [35]. In fact, questing I. ricinus ticks are active when the daily maximal temperature has reached 7°C over 5 days [29]. Adults and nymphs usually emerge first, followed by larvae. Questing tick density increases progressively as weather conditions get warmer [29] until peak density is recorded in spring, usually between April and June [34]. Questing density then decreases gradually due to decreasing numbers of unfed ticks still seeking a host and to increasingly drier weather conditions [29,31], so that I. ricinus ticks rarely quest during summer, except at higher altitudes where the climate is milder [33,34]. In autumn, when favourable conditions of temperature and humidity are back, a second peak of questing ticks may be observed [34]. However, the autumn peak is of lower intensity than the one observed in spring and is absent if weather conditions are unfavourable [29,31,34]. The last questing I. ricinus ticks are usually sampled in October or early November [34] as ticks return progressively to an inactive state during winter [26,78]. Larvae: green; nymphs: red; adults: blue.