I realize that your bees are not working cotton but bees working cotton look
exactly as you described at the hive entrance.  Cotton pollen is white.  I
have never seen a bee collect or store cotton pollen.  Our local beekeeping
association supports Alabama A & M University on honey bee study programs
one of which was:

"IMPACT OF HONEY BEE POLLINATION ACTIVITIES ON Bt COTTON PRODUCTION IN
NORTHERN ALABAMA"
http://home.hiwaay.net/~martinb/impact_of_honey_bee_pollination_.htm.

The following does not address your question but I find it very interesting:
During one of our visits to the experiment field we observed a honeybee fly
from a cotton bloom to a cotton leaf.  She was near solid white.  She held
onto the leaf with one leg and was brushing the pollen from her body with
her other legs.

In summary, you could be seeing pollen on the bees body and no similar
looking pollen on the pollen baskets or in the combs.

Bob Fanning
Huntsville, AL USA 

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