Thank you to all who contributed and answered my question in
various forms.  I did in fact, finally, remember where I had seen
the Eckert reference and found the information I required.  I was
after, in fact, a 'scare' distance.  I need to refer to the
maximum distance that bees had been known to fly to forage,
rather than an *effective* distance beyond which it is unlikely
they would forage efficiently.  It related to the distance from
beehives that pest control officers were to place a substance
that was (1) poisonous to bees and (2) attractive to bees.  We
had previously quoted the 3-5 km as being a 'normally expected'
foraging distance, but wanted also to give an extreme that could
be substantiated.  As for those extreme distances, I have always
quoted some mythical person who referred to bees ability to know
distance to source, quantity of source and quality (sugar
content) and that bees were able to 'put these together' to know
if a particular source was (net) better than another and whether
a source was (net) better than just staying home (does it cost
more energy to fly there and back than is brought back?).  Again,
thank you for assisting me - I found the answers informative and
interesting.
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          Nick Wallingford
      Bay of Plenty Polytechnic
 (East coast, N Island, New Zealand)
     Internet [log in to unmask]
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