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1. Eastern tent caterpillars (Malacosoma americanum) are broadly distributed within North America, with populations spanning a wide range of environmental conditions. Their egg masses are consistently attacked by a variety of wasps in the superfamily Chalcidoidea. We performed a reciprocal transplant‐type experiment to assess the performance of three populations spanning 15° of latitude when subjected to temperature regimes resembling southern or northern conditions. 2. Exposure to warm temperatures and short overwintering periods (southern conditions) resulted in the increased survival of both caterpillars and parasitoids from all populations. By contrast, the ability of caterpillars to withstand starvation was maximised when exposed to conditions similar to their native region. 3. Caterpillar and wasp phenology differed among populations even when exposed to the same temperature regime. Individuals exposed to novel conditions hatched 2–6 weeks later than those experiencing native conditions. Under typical conditions, the relative phenology of wasps and their hosts exhibited a latitudinal gradient consistent with growing season length, with southern, central, and northern wasps, emerging 50, 45, and 36 days, respectively, after their hosts. 3. We identified four genera of primary parasitoids, which emerged within a narrow 2‐week span, and one hyperparasitoid, which emerged in distinct pulses over an approximately 5‐week span, possibly indicating the presence of a second generation. 4. Caterpillars and wasps exhibited distinct phenological responses according to population of origin, indicating that not only pre‐hatching winter and spring conditions, but also historical factors, which may include local adaptation, maternal effects, and oviposition time, influence their phenological responses. The period between eastern tent caterpillars hatching and the emergence of their egg parasitoids exhibited a latitudinal gradient consistent with growing season length.We identified four genera of primary parasitoids, which emerged within a narrow 2‐week span, and one hyperparasitoid, which emerged in distinct pulses over an approximately 5‐week span.Caterpillars and wasps exhibited distinct phenological responses according to population of origin, indicating that not only pre‐hatching winter and spring conditions, but also historical factors influence their phenological responses. [ABSTRACT FROM AUTHOR]

Climate change is disrupting species interactions by altering the timing of phenological events such as budburst for plants and hatching for insects. We combined field observations with laboratory manipulations to investigate the consequences of climate warming on the phenology and performance of the eastern tent caterpillar ( Malacosoma americanum). We evaluated the effects of warmer winter and spring regimes on caterpillar hatching patterns and starvation endurance, traits likely to be under selection in populations experiencing phenological asynchrony, using individuals from two different populations (Washington, DC, and Roswell, GA). We also quantified the proximate and extended fitness effects of early food deprivation and recorded spring phenology of local caterpillars and their host plants. In addition, we conducted laboratory assays to determine if caterpillars are using plant chemical cues to fine-tune their hatching times. Warmer winter temperatures induced earlier hatching and caterpillars from GA survived starvation for periods that were 30 % longer than caterpillars from DC. Warmer spring regimes reduced the starvation endurance of caterpillars overwintering in the wild but not in the laboratory. Early starvation dramatically reduced hatchling survival; however, surviving caterpillars did not show detrimental effects on pupal mass or development time. In the field, hatching preceded budburst in both 2013 and 2014 and the period of optimal foliage quality was 2 weeks shorter in 2013. Hatching time was unaffected by exposure to plant volatiles. Overall, we found that warmer temperatures can trigger late-season asynchrony by accelerating plant phenology and caterpillars from different populations exhibit differential abilities to cope with environmental unreliability. [ABSTRACT FROM AUTHOR]