Background
Mostly due to climate warming and its associated environmental changes, recent studies have revealed the expansion of the geographical distributions of several species, including many European [1-4], American [5], and Japanese [6-8] butterflies. Although habitat associations are generally constrained at range margins, physiological adaptation was observed in British butterflies in the range expansion process [1,3,4]. In these cases, the habitat variations that certain butterfly species can colonize increased over time [1,3,4]. Such changes are well within the range of normal physiological adaptation to different environmental conditions.