Discussion
The objective of this study was to experimentally disentangle the role of warming temperatures in Spring from the emergence of susceptible hosts on the timing of seasonal parasite outbreaks. Using a range of constant temperatures and availability of susceptible hosts, we found that temperature influenced both host and parasite development, but that–consistent with our main hypothesis­–parasite development was more strongly limited by low temperatures than host development. Variation in host susceptibility modifies this pattern, with more susceptible clones becoming infected faster than more resistant ones and with hatchlings borne from ephippia less likely to become infected then those produced asexually.