In this research we studied the resonant reflection of circularly polarized light from a chiral stack of twisted ultra-thin
birefringent layers such as found in the exocuticle of the beetle Proagoderus brucei. This beetle is interesting as it
belongs to a very small group of species exhibiting different colors on different parts of its body. Measurements were compared with a computer model of the structure. In this way observations could be explained, some unknown parameters could be quantified and the properties of similar artificial structures with possible practical applications can be predicted.