Fatty acid and carbon isotopic data for: Use of essential vs. non-essential fatty acids during flight in monarch butterflies: Implications for the importance of nectaring during migration

Many insect species are migratory, but migration is energetically costly, leading to a tradeoff between migration and subsequent reproduction. Of importance to the allocation of resources to migration and reproduction is the relative use of essential and non-essential fatty acids. How different ecological conditions experienced by individuals affect the differential allocation of nutrients has not been well explored, especially in insects. Our goal was to evaluate how reproductive (summer) and migratory (fall) rearing conditions affect the source and allocation patterns of fatty acids used during experimental flights (0-6h) in monarch butterflies (Danaus plexippus L.). We used larval and adult diets manipulated isotopically (δ13C) and chromatographic analyses to determine fatty acid composition and source in the fat body. C4 vs. C3 carbohydrate feeding increased the δ13C value of lipids in monarchs (-31.2 vs -22.1‰) and increased total fatty acid concentrations reflecting lipid synthesis during adult feeding. Fuel use during flight differed with essential fatty acids being more conserved in fall vs. summer conditions (21% vs 32% loss respectively) indicating that the environmental cues responsible for the onset of migration result in physiological changes that modify lipid use. Frequency of stopovers for nectar and nectar quality available during migration will influence the capacity of monarchs to conserve essential fatty acids up to and through migration and overwinter period.