Apparently moonlight is polarized:

http://news.nationalgeographic.com/news/2003/07/
0702_030702_dungbeetle.html

Observations done on A. dorsata have shown that it forages when the
moon is between half-full and full. The dance run indiciates the
direction not of the moon, though, but the (hidden) sun.
    -----Eva Crane----

Regards,
Dick Allen

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