[Ecology of the tick, Dermacentor silvarum O1]

Results of the experiments have shown that the development of Dermacentor silvarum from egg to imago varied from 44 to 46 days at 28 C and redundant humidity and from 50 to 52 days at 25 degrees C. The thermic threshold of larval development lies within a range of 8.6 degrees C, that of nymphs-9.7 degrees C. A sum of effective temperatures required for larval development averaged 123.5 degrees C, for nymphs-225 degrees C and for the whole ontogenesis-from 570 to 690 degrees C. In the north of the distribution area of D. silvarum this species seems to occur only in those localities, where a sum of effective temperatures is higher than 10 C and makes not less than 570 degrees C.