The following is from a book called "Protein Content and Amino-acid Profiles of
 Honeybee-collected Pollens" by Peter Stace.  This is Australian conditions.

 "Corn or maize is a pollen source utilised by bees.
  Corn pollen is 14% to 15% crude protein and amino-acid ratios are
 satisfactory, the iso-leucine being 3.7% to 4.3%.

 Bees collect corn pollen in large quantities and are stimulated to breed.
 This is interesting as corn does not produce nectar.  Any major bee-breeding
  that occurs with corn pollen as the main protein source would produce
 low-protein bees.  Diseases such as EFB and nosema may result.

 Because corn pollen is so enthusiastically collected and eaten by honey bees,
 it possibly could be used for collecting, storing and feeding back to bees as
 an additive to soyflour."

 My own experience is that bees collect vast quantities of corn pollen.  It is
 good for maintainimng hives such as mating nucs but as stated above if they
 try to expand, the hive will diminsh at a later stage down the track unless it
 is shifted onto a better source of pollen.

 The attractiveness of corn is a problem where they grow sweet corn as it is
 sprayed here about every second day.  Large losses of field bees can be
 experienced if they use some of the more deadly chemicals.  We are lucky where
 we are as they grow the corn for silage and hence do not spray.

 Another beekeeper I know has bees on corn where it is planted every week and
 is picked for sale for eating.  This grower does not spray.  The grower says
 he gets better filled out cobs as the bees collecting the pollen are also
 making pollen drop down onto the stigmas.  This being especially on still
 mornings with no wind to carry out the normal pollination.

 Hope this helps.

 Trevor Weatherhead
 AUSTRALIA