If the bee disappears from the surface of the earth, man would have no more than four years to live. No more bees, no more pollination ... no more men!

A variant — "Professor Einstein, the learned scientist, once calculated that if all bees disappeared off the earth, four years later all humans would also have disappeared" — appears in The Irish Beekeeper, v.19-20, 1965-66, p74, citing Abeilles et Fleurs (Bees and Flowers, the house magazine of Union Nationale de l'Apiculture Française) for June 1965. Snopes.com mentions its use in a beekeepers' protest in 1994 in Europe suggesting invention and attribution to Einstein for political reasons.