High temperature and soil moisture reduce host‐plant quality for an insect herbivore

1. Anthropogenic climate change is a substantial threat to global biodiversity. It may affect insect herbivores directly and indirectly. Indirect effects are, among others, mediated by climate‐change induced variation in host‐plant quality. Although being potentially important, little is known on the significance of such indirect effects and on interactions among environmental stressors in plant–herbivore interactions. 2. To simulate the potential impact of climate change, we investigated effects of host‐plant temperature and soil moisture on herbivore performance in the tropical butterfly Bicyclus anynana under laboratory conditions. 3. Maize grown at high temperatures or under wet conditions reduced herbivore performance, indicated by decreased body mass, storage reserves, phenoloxidase activity, and increased development time. Temperature and soil moisture acted largely independent of one another. Detrimental effects of the high plant temperature were restricted to males, indicating a higher vulnerability of this sex to environmental stress. 4. In nature, B. anynana might be threatened by increasing temperatures during the wet season negatively affecting host‐plant quality. Our study shows that herbivore performance can be substantially affected by indirect effects mediated through changes in host‐plant quality, which deserves more attention in the current era of global climate change