Abstract
Chrysidid wasps in the subfamily Chrysidinae are brood parasitoids or cleptoparasites of other insects and famous for their cuticular iridescence. In this study, we examine the dorsal abdominal cuticle of the chrysidid wasp Hedychrum rutilans to identify the underlying color mechanism. Using scanning electron microscopy, reflectance spectral analysis, and theoretical calculations, we demonstrate the presence of an epicuticular multilayer reflector consisting of six lamellae with a thickness of 185 nm each. The lamellae exhibit a rough surface probably functioning as spacers between the individual layers. The reflector has a measured reflectance maximum at λ = 630 nm, i.e., in the red part of the visible spectrum of light at normal incidence and the reflectance maximum shifts to green as the angle of incidence increases. Complementary theoretical modeling corroborates the view that the epicuticular multilayer generates the iridescent color of the chrysidid cuticle.
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Acknowledgments
The study was partly supported by the EU through FP6 BIOPHOT NEST/Pathfinder 012915 project and by a grant of the German Science Foundation, DFG, Bonn (STR 532/1-2). The authors acknowledge the use of Namur Interuniversity Scientific Computing Facility Namur-ISCF, a common project between the Belgian FNRS and the University of Namur, Belgium. C. Vandenbem is a postdoctoral researcher of the FRS-FNRS. The authors thank Victoria Welch for helpful discussions and Wolfgang Göttler for his help with preliminary SEM investigations. The experiments carried out in this research comply with the current laws in Germany and Belgium.
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Fig. S1
Dorsal view of the abdomen of H. rutilans (Hymenoptera, Chrysididae), parasitoid of the European beewolf Philanthus triangulum (Hymenoptera, Crabronidae). The strongly iridescent coloration is red at perpendicular view and turns green and blue under larger incidence (JPEG 896 kb)
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Kroiss, J., Strohm, E., Vandenbem, C. et al. An epicuticular multilayer reflector generates the iridescent coloration in chrysidid wasps (Hymenoptera, Chrysididae). Naturwissenschaften 96, 983–986 (2009). https://doi.org/10.1007/s00114-009-0553-6
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DOI: https://doi.org/10.1007/s00114-009-0553-6