Does anyone have any good tricks on how to identify which hive in an apiary
is the aggressive one?  I have 5 hives sitting about 25 ft west of my garden.
 The hives are about 10 ft apart.  Starlines or derivatives.  I have had no
problems when working the hives this year (switching boxes, adding supers,
feeding, treating for mites, etc).  But when working in my garden (not doing
anything to the bees) on several occasions this spring, I have been
repeatedly dive-bombed by aggressive bees.  Just a few, but they don't give
up.  They don't bother me when I stand among the hives, just when I'm about
50 ft out in front of them.  It's rather embarassing, but I can't figure
which one is the naughty one.  Any ideas?

Thanks in advance,
Matt Higdon
mid-MO, mid-USA