Autumn larval cold tolerance does not predict the northern range limit of a widespread butterfly species

Climate change is driving range shifts, and a lack of cold tolerance is hypothesized to constrain insect range expansion at poleward latitudes. However, few, if any, studies have tested this hypothesis during autumn when organisms are subjected to sporadic low temperature exposure but may not have become cold tolerant yet. In this study, we integrated organismal thermal tolerance measures into species distribution models for larvae of the Giant Swallowtail butterfly, Papilio cresphontes, living at the northern edge of its actively expanding range. Cold hardiness of field-collected larvae was determined using three common metrics of cold-induced physiological thresholds: the supercooling point (SCP), critical thermal minimum (CTmin), and survival following cold exposure. P. cresphontes larvae in autumn have a CTmin of 2.14°C, and were determined to be tolerant of chilling. These larvae have a SCP of -6.6°C and can survive prolonged exposure to -2°C. They generally die, however, at temper...