"We must avoid opening the hive too brusquely; in separating the combs we must act slowly, taking care to wound none of the bees: when they are too much clustered upon the combs we must brush them softly with a feather, and, above all things, not breathe upon them; the air which we exhale appears to anger them: the nature of this air evidently possesses some irritating quality; for if we use bellows to blow upon them, they are rather inclined to escape than to sting."--Francis Huber, New Observations Upon Bees, Volume I, 13th Letter, pg 192 of the 2012 edition
Link to 1806 English edition:
http://www.bushfarms.com/huber.htm#humanbreath"Bees dislike the offensive odour of sweaty animals, and will not endure impure air from human lungs"--L.L. Langstroth, The Hive and the Honey Bee