Comma butterflies (Polygonia c-album) in Scandinavia can eat plants from several different families (Fig. 1). This kind of diet plasticity (generalization) is rare among herbivorous insects, butterflies in particular. The plants differ in both secondary chemistry and nutrition, suggesting that Comma larvae may use different molecular and physiological mechanisms to safely and efficiently metabolize tissue from these plants. We sequenced mRNA from the midguts of 4th instar larvae feeding on one of three different host plant genera: Ribes (gooseberry), Salix (willow) and Urtica (nettle) (Fig. 2). Using these RNA-seq data, we will investigate differences in the larval gut transcriptome that contribute to the ability to eat such divergent host plants.