House Fly, Vol. 7, No. 18
Musca domestica
Order: Diptera
Family: Muscidae
“Close that door! You're letting flies in!” Growing up on a farm, in a home with no air conditioning, this was an admonition I heard often as a boy. At that time, keeping the screen door closed and frequent use of the fly swatter were the two best ways to control house flies. Fly tape and Golden Malrin Fly Bait were also deployed in the summer months when fly numbers were greatest.
House flies can still be vexing indoor pests, but the improved insect exclusion that comes with air conditioning, the improved sanitation that comes with modern sewage management, and the relative lack of large animals in urban settings means house flies are not nearly as common as they used to be. Like bed bugs and German cockroaches, houseflies are one of those pests that just can’t live without us. You won’t find house flies in uninhabited woods or deserts; they only thrive near humans, or around animal production facilities maintained by humans. But house flies are still important pests, even in urban settings. You can probably spot one or more in one of the next five or six restaurants you enter.
House flies breed in a wide range of moist, decaying organic matter. Animal manure, including feces of dogs and cats, as well as human waste are favorite breeding sources, but they also breed in garbage and decaying plant material, such as grass clippings. Females lay their eggs on these materials and the resulting maggots feed there for days or weeks before crawling to a dryer, protected location to pupate. Development rate depends on temperature. Under optimum conditions house flies can complete a generation in 10 days or less, but yearly averages are longer. There are around ten to twelve generations per year.
Houseflies are often grouped with blow flies and flesh flies, which are similar in size and breeding habits, and collectively referred to as filth flies, a very appropriate name for this group. Adult house flies are said to have “sponging mouthparts,” because they feed by depositing salivary secretions onto the food substrate to liquify it and then sucking up the resulting liquid. They will also defecate while feeding or when at rest. What was that fly feeding on before it lit on your French fry?
Sorry to be overly graphic here, but if this image causes you to be more vigilant in shooing flies away from your food, then that’s a good thing. House flies have been proven to carry more than 100 human pathogens, though the ability to find these pathogens on house flies does not always mean they are able to spread all these pathogens to humans. But house flies are proven vectors of many food-borne diseases that can cause food poisoning, diarrhea, and dysentery. As my Grandmother succinctly explained, “Flies are nasty, and you don’t want them crawling on your food.”
Control: In homes, restaurants and other commercial businesses, sanitation and exclusion are the most important tools for fly control. Once flies enter a building, non-chemical controls such as UV light traps and even fly swatters are preferred over insecticides. See pages 37-40 of Extension Publication 2443, Control Household Insect Pests for more information.
Blake Layton, Extension Entomology Specialist, Mississippi State University Extension Service.
The information given here is for educational purposes only. Always read and follow current label directions. Specific commercial products are mentioned as examples only and reference to specific products or trade names is made with the understanding that no discrimination is intended to other products that may also be suitable and appropriately labeled.
Mississippi State University is an equal opportunity institution.
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