Interspecific differences in the questing behaviour of Dermacentor andersoni and Dermacentor variabilis (Acari: Ixodidae) larvae

Abstract

Dermacentor variabilis and Dermacentor andersoni (Acari: Ixodidae) parasitise the same range of hosts in western Canada and have largely allopatric ranges except for a zone of sympatry in southern Saskatchewan, where these species experience the same environmental conditions. We report herein the discovery of differences in the behaviour of D. variabilis and D. andersoni larvae after they emerge from eggs. A behavioural diapause observed in D. variabilis larvae was not detected in D. andersoni larvae that were exposed to the same environmental conditions. As unfed D. variabilis larvae can successfully overwinter, their behavioural diapause represents an adaptive strategy to synchronise their questing activity and life cycle stage to maximise the chance of larvae encountering a suitable rodent host at the onset of spring. Such strategy will be of a significant benefit for colonising individuals at the northern edge of the distributional range of D. variabilis.