Factors affecting transmission of larval winter ticks, Dermacentor albipictus (Packard), to moose, Alces alces L., in Alberta, Canada.

The larval stage of the winter tick, Dermacentor albipictus, was studied under field conditions in central Alberta, Canada. Larvae ascended vegetation in autumn, possibly in response to photoperiod. Numbers found by flagging increased from early September to early October and decreased gradually to zero by December. Larvae clumped on the tips of vegetation approximately 1-1.5 m off the ground, and did not exhibit a diurnal, vertical migration. Activity was temperature dependent and no obvious preference of vegetation species for ascension was detected. Transmission of larvae to moose was probably facilitated by synchrony of the larval activity period with the moose breeding season in autumn.