Diapause is but one of the many ecophysiological responses by which the development, growth, and reproduction of an arthropod is synchronized with the seasonal changes in its environment, as well as the availability of food and other essential resources. Diapause affects the seasonal occurrence of tick-borne arboviral infections, fostering epizootic outbreaks coincident with the onset of tick host-seeking behavior. In nature, tick borne viruses persist principally in their tick vectors with the warm blooded bird and mammal hosts acting chiefly as amplifiers. A variety of regulatory schemes occur in insects and other arthropods, and ticks are no exception. These range in complexity from no apparent regulation to seasonal cycles that are exquisitely synchronized with the optimum period of host availability and climatic conditions favorable to development and reproduction. Photoperiod is probably the most important environmental factor controlling the induction and termination of diapause, with temperature playing a significant but secondary role.