About UV for navigation.  UV light is not the same as the other colours we
can see in the sky.  UV has a pattern with a depression of brightness in the
line of sky perpendicular to the trajectory of the sun.  This line changes with
the movement of the sun, so that bees not only can detect N, S, W, and E but
also the hour if they cannot see the sun.
Tomas
[log in to unmask]