has been measured in several other scarab beetles such as Chrysina gloriosa, as well as some crustaceans such as the mantis shrimp. In these cases, the underlying mechanism is the molecular-level helicity of the chitinous cuticle. The bioluminescence of the larvae of fireflies is also circularly polarized, as reported in 1980 for the species Photuris lucicrescens and Photuris versicolor. For fireflies, it is more difficult to find a microscopic explanation for the polarization, because the left and right lanterns of the larvae were found to emit polarized light of opposite senses. The authors suggest that the light begins with a linear polarization due to inhomogeneities inside aligned photocytes, and it picks up circular polarization while passing through linearly birefringent tissue. Water-air interfaces provide another source of circular polarization. Sunlight that gets scattered back up towards the surface is linearly polarized. If this light is then totally internally reflected back down, its vertical component undergoes a phase shift. To an underwater observer looking up, the faint light outside Snell's window therefore is (partially) circularly polarized. Weaker sources of circular polarization in nature include multiple scattering by linear polarizers, as in the circular polarization of starlight, and selective absorption by circularly dichroic media. Radio emission from stars and pulsars can be strongly circularly polarized. Two species of mantis shrimp have been reported to be able to detect circular polarized light. See also Polarizer 3D film Chirality Sinusoidal plane-wave solutions of the electromagnetic wave equation Starlight polarization Waveplate References Further reading External links Circularly polarized light: beetles and displays Article on the mantis shrimp and circular polarization Animation of Circular Polarization (on YouTube) Comparison of Circular Polarization with Linear and Elliptical Polarizations (YouTube Animation) Reversal of handedness of circularly polarized light by mirror. A demonstration – simple, cheap & instructive Polarization (waves) Stellar astronomy Astrophysics