Many studies have addressed several plant-insect interaction topics at nutritional, molecular, physiological, and evolutionary levels. However, it is still unknown how flexible the metabolism and the nutritional content of specialist insect herbivores feeding on different closely related plants can be. We performed elemental, stoichiometric, and metabolomics analyses on leaves of two coexisting Pinus sylvestris subspecies and on their main insect herbivore; the caterpillar of the processionary moth (Thaumetopoea pityocampa). Caterpillars feeding on different pine subspecies had distinct overall metabolome structure, accounting for over 10% of the total variability. Although plants and insects have very divergent metabolomes, caterpillars showed certain resemblance to their plant-host metabolome. In addition, few plant-related secondary metabolites were found accumulated in caterpillar tissues which could potentially be used for self-defense. Caterpillars feeding on N and P richer needles had lower N and P tissue concentration and higher C:N and C:P ratios, suggesting that nutrient transfer is not necessarily linear through trophic levels and other plant-metabolic factors could be interfering. This exploratory study showed that little chemical differences between plant food sources can impact the overall metabolome of specialist insect herbivores. Significant nutritional shifts in herbivore tissues could lead to larger changes of the trophic web structure.

• Keywords
• herbivory, metabolomics, plant-insect, processionary moth, scots pine, secondary metabolites, stoichiometry,
• MeSH
• Principal Component Analysis MeSH
• Pinus sylvestris metabolism   parasitology   MeSH
• Herbivory MeSH
• Species Specificity MeSH
• Nitrogen analysis   MeSH
• Phosphorus analysis   MeSH
• Mass Spectrometry MeSH
• Host-Parasite Interactions MeSH
• Larva chemistry   physiology   MeSH
• Plant Leaves chemistry   metabolism   parasitology   MeSH
• Metabolome * MeSH
• Metabolomics * MeSH
• Moths growth & development   physiology   MeSH
• Feeding Behavior MeSH
• Chromatography, High Pressure Liquid MeSH
• Animals MeSH
• Check Tag
• Animals MeSH
• Publication type
• Journal Article MeSH
• Names of Substances
• Nitrogen MeSH
• Phosphorus MeSH