In this chapter the occurrence of circularly polarized (CP) light in nature (both in the abiotic and biotic optical environment) is surveyed. We deal with the reason and the possible adaptive significance of CP light reflected from the exocuticle of many beetle species belonging to the Scarabaeoidea. This unique feature of the insect exocuticle seems to have evolved only in scarabaeoids. The imaging polarimetry of circularly polarizing scarab beetles and its results are reviewed. The alleged CP sensitivity in Chrysina gloriosa scarabs is briefly discussed. Finally, the experimental evidence for the lack of CP vision in the scarab species Anomala dubia, A. vitis (Coleoptera, Scarabaeidae, Rutelinae), Cetonia aurata, and Protaetia cuprea (Coleoptera, Scarabaeidae, Cetoniinae) with circularly polarizing exocuticle is presented.