The association of: flies with man has been recorded through many centuries. In nearly all of these records the association is one of discord rather than harmony. In the Book of Exodus, 8:24, in the King James version of the Old Testament, we can read, "...and there came grievous swarms of flies into the house of Pharaoh, and into his servants' houses; and in all the land of Egypt the land was corrupted by reason of the swarms of flies." Centuries later the "grievous swarms of flies" 'were associated with a particular disease by Mercurialis. In 1577 he expressed the belief that flies carried the "virus" of plague from those ill or dead of plague to the food of those not yet ill of plague (8).