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The Filthy House Fly


The Filthy House Fly

The House Fly


The common house fly is also known as the "filth fly" because it can contaminate foods and surfaces by simply landing on them. The fly sitting on the edge of your glass may very well have come directly from feasting on trash, manure, or other waste.

The description on the website of the U.S. Department of Agriculture's Agricultural Research Service (USDA/ARS) begins: "It's common knowledge that house flies are carriers of disease. That's why there's such widespread effort to keep them out of our kitchens and away from our food." As their name indicates, house flies are commonly found around the home. In fact, because they breed and feed on human food and waste, they are generally found about anywhere that humans are.


  • House flies are about ¼ inch long.
  • They are grayish in color.
  • They have broad, dark stripes down the mid-section of their bodies.
  • Their most dominant feature is their large, reddish, compound eyes.

Non-Biting Fly

The house fly does not bite - because it can't. It has "sponging" mouth parts, so it can only suck up liquids. If you are bitten by a large fly, it is most likely a horse fly, deer fly, stable fly, or black fly.

Why Can't I Swat It?

It is the fly's compound eyes, tiny body hairs, and speed that make it so difficult to swat. The eyes and hairs enable it to sense changes in airflow, so that well before your fly swatter gets close, it has flown off. This along with its ability to fly at speeds of 5 mph - with bursts of up to 15 mph when threatened, give this fly the power to be well away before your hit can land.

Habits and Behavior

In addition to feeding on garbage, the house fly also lays its eggs on garbage, animal feces, and other decaying organic material, such as lawn clippings.

The eggs hatch within a day, and the emerging maggots feed on the waste to develop into adult flies in less than a week. The fly can travel up to 20 miles, but it generally stays within two miles of where it hatched.

A fly can live about a month, and in this time, the female fly can lay about 2,000 eggs in batches of 75 to 100.

Most prevalent in spring and summer, these flies often enter homes through open doors and windows, but they can also get in through cracks around doors and windows, torn screening, and similar small openings.

Why House Flies Are a Problem

They spit on your food. The house fly can only digest liquid food. So when it lands on your sandwich, it regurgitates saliva onto it, then sucks in the liquid this creates-or most of it anyway. Some of that saliva is likely to still be on the bread when you go to take your next bite.

They leave specks. Those little black dots that you see in places where flies have spent a bit of time are their feces that they let drop at random.

They fly from trash to table. The house fly cares little whether it feasts on food from the trash or your table, and it will fly back and forth between the two, with the ability to carry more than a million bacteria on its feet and body!

They can carry disease. According to university reports, including the University of Rhode Island and Penn State, at least 65 diseases have been associated with house flies. The bacteria and viruses it carries can cause food poisoning, diarrhea, eye infections, dysentery, cholera, and tuberculosis.

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