I believe that kids like mystery, so how about a fact that is still half
mystery:
 
Bees use their bodies to manufacture very tiny crystals of magnetite which
they can use as compasses to tell direction on days when they can't see the
sun (and when the cloud cover is so dense that they can't even tell where
the sun is from the polarization of light--but this might be much for that
age group).  Nobody knows yet how the bees are able to sense which way the
extremely small "magnets" are pointing.