Temporal stability of ?2H in insect tissues: Implications for isotope-based geographic assignments

Hydrogen isotope geolocation of insects is based on the assumption that chitin in wings adult migratory preserves hydrogen composition ( ? 2 H) larval stages without influence diet. Here, we test this by conducting laboratory feeding experiments for monarch butterflies Danaus plexippus ) including: (1) a starvation treatment where adults were not fed and (2) an enriched diet isotopically deuterium (~ +78‰) compared to The H values measured at different time steps along 24-day experiment. We also investigated intra-wing differences caused wing pigmentation, absence scales, presence major veins. conclude that, although magnitude changes are small (~6‰), vary insect age, particularly early after eclosion (i.e., 1–4 days). found shade, scales do alter values. However, samples containing veins had systematically higher (~9‰), suggesting influences hemolymph circulates hypothesise there stronger signal during life relative later because increased metabolic physiologic activity young wings. argue isotopic contribution generally likely minimal if carefully sampled avoid demonstrated inert tissues, contributes some intra-population variance. using remains valid, but feeding, butterfly age vein sampling generate inherent uncertainty limiting precision geolocation.