How the dung beetle finds its way home using polarised vision

The dung beetle spends most of his time rolling around balls of... well... dung. These balls are so large that he cannot really see where he is going. Fortunately, he has polarised vision and he uses the sky polarisation to navigate. Amazingly, he doesn't only observe the blue sky during the day, but he can apply the same trick during the night when the moon is up.