The idea has been mooted that the sheep tick (Ixodes ricinus L.) is active at different times on different host species. Tick-activity curves for sheep, deer, hare, rabbit, skylark and meadow-pipit are similar in form and timing. With these animals, therefore, there is no indication of any marked individual species effect on activity.

Where spring activity occurs, males, females and nymphs usually have similar and concurrent activity curves, but nymphs may occasionally have their peak 2–3 weeks later than adults. Larval activity is always later, the peak being several weeks after the female peak. The data for nymphs amend the general statement on activity in a previous paper by the present author.

Ticks are active during the hours of darkness but the activity-density then is considerably less than in daylight. This diurnal fluctuation in activity seems to follow fairly closely the diurnal fluctuation in atmospheric temperature.