The Domestic Fly Is No Saint
The house fly Musca domestica has been an associate of humankind throughout recorded history. From the times of the Bible, "And there came a grievous swarm of flies into the house of Pharaoh..." (Exodus 8:24), and Aristotle, who is said to have been fascinated by the mating behavior of these two-winged insects, to the 20th century, almost every person recognizes a fly when they see one.
Even the species name, domestica, suggests that the house fly lives in close contact with humans. Some authorities believe that the association of house flies with people is more than a superficial relationship. These insects depend on us for subsistence.
Immature house flies are ecologically known as saprophytes, living organisms that feed on dead and decaying things. House fly food includes garbage and animal and human manure. Historically, house fly populations are high when there is an abundance of food for their larvae. Consequently, as sanitation practices improve, house flies are less abundant.
In the United States, house fly populations decreased in many areas as sewage systems developed and replaced outdoor privies. In addition, transportation changed from the horse to the horseless carriage, and a fly-breeding site — horse manure at the side of the road — became scarce. So there are probably fewer house flies today than when Grandpa was a kid.
Having fewer house flies is something most of us can tolerate. Indeed, the house fly can carry disease organisms on each of its six feet. For that reason, an effort was made at the turn of the century to establish the name "typhoid fly" for what we know as the house fly. The reason was that typhoid fever was one of the most serious diseases carried by this insect. Luther West, in his book "The Housefly," suggests that "cholera fly" or "dysentery fly" also would be appropriate names. These names recognize that the insect can transmit a number of diseases as it moves from breeding sites to our dinner table, where it happily walks around on our food.
Window screens and fly swatters came into widespread use during the early part of the 1900s, partially in an effort to keep house flies from contaminating our food. Fly swatters were popular advertising items during this time. Many swatters included such slogans as "swat the fly and prevent disease."
While modern sanitation and insecticides have reduced the potential of house-fly borne diseases in modern societies, the problem still exists in many developing areas. But even today we are sometimes reminded of the past when grandma bakes a "shoo-fly pie," a pie so named because it was necessary to shoo the flies from the pies as they cooled on the windowsill — a good idea because the flies had no doubt come from the privy or the barnyard. And the thought of having them tromping in our pies was not very appetizing!