I don't know about cornmeal, but I planted 72 Zinnias in my front yard
last spring. I have never seen so many visits from bees in years. They
love the flower. So do butterflies.

John Savage wrote:

On a recent radio gardening program, a listener rang in to say he
discovered that bees love cornmeal. He spreads cornmeal around his
garden and the bees flock to it. I got the impression that he uses
it uncooked and unsweetened--just the polentia flour straight out
of the packet, and sprinkled around the garden near to or on the
plants whose flowers he wants pollinated.

Try it when your garden needs bees, and let us know the results.
--
John Savage, trying his best to report with no trace of scepticism