Diel activity of adult taiga ticks Ixodes persulcatus in the north-western part of its range (Karelia, Russia).

The taiga tick Ixodes persulcatus (Schulze, 1930) (Acari, Ixodidae), widespread in the northern Palearctic, is the vector of dangerous human pathogens including tick-borne encephalitis virus. Knowledge of its ecology is important for minimising tick bite exposure risk. We studied the diel activity of male and female I. persulcatus in the north of the range (Karelia, Russian Federation) and tested its relationship with environmental factors including temperature, relative humidity and light intensity. The field experiment was conducted in May-June 2024. Cages with unfed adult ticks (males and females) were placed in three different biotopes, and their activity was assessed every two hours. Tick activity could be described by a bimodal curve, with a peak in the morning and in the evening. Diel activity rhythms were somewhat different in male and female ticks, with females questing longer than males. Relative humidity was the key determinant of questing duration. Weather changes accompanied by decreasing atmospheric pressure, as well as rain, reduced tick activity. The greatest tick bite exposure risk in Karelia is observed from mid-May to early June, when the temperature ranges from 10 °C to 20 °C and relative humidity exceeds 70%.