Synchrotron-X-ray fluorescence provides elemental signatures for diverse coloration mechanisms in fossil insects

Numerous fossil insects exhibit color patterning, but the coloration mechanisms responsible are largely unknown. Here, we use non-destructive SRS-XRF to characterize the spatial distributions of elements in the cuticles of 78 extant and 15 fossil insects collected from six independent fossil localities. LDA reveals a strong taxonomic signal whereby members of the same order or family show similar chemical signatures. Within genera, cuticle regions containing different pigments have distinct chemistries, i.e. broad taxonomic trends in chemistry are overprinted by a strong pigment-specific signal. The chemistry of fossil insect cuticles differs to that of extant analogues and is controlled by both taxonomy and depositional context, indicating diagenetic overprinting of original cuticle chemistry. Despite this, cuticle regions with different visual tones in fossils contain specific suites of elements, suggesting that original color influences the preserved chemical signal.