Data on life history traits
We used data on four key life history traits to potentially explain shifts in phenology and NRB, and in population trends. The trait variables used included: body size (continuous variable), overwintering stage (factor with four levels: Adult, Larvae, Pupa, Egg), specificity of larval host plant use (factor with two levels: Generalist, Specialist), and voltinism (factor with two levels: Univoltine, Multivoltine). These traits were chosen as they were linked to variation in responses to climate and environmental change in previous empirical studies on Lepidoptera (Pöyry et al. 2009, 2017; Betzholtzet al. 2013; WallisDeVries 2014), and because information on these traits is available for both moths and butterflies. See Fig. S3 for further details and data sources.