House Flies


Adult house flies are about 5/16-inch long and have a gray-colored body with four dark lines on their back. Larvae are about ½-long and are creamy-colored. Adults have two wings and large reddish-colored eyes.


House flies are active during the day, especially during the warmest and driest portion of the day. Adult house flies are not active at night, but will move to sources of light during the night. However, they mostly rest on surfaces such as ceilings, overhead wires and shrubs and trees.

House flies are found in human and animal wastes and filth such as garbage, feces and dead animals. A group of field researchers in Texas found that breeding and developmental sites, in order of most to least preferred, included horse manure, human feces, cow manure, fermenting vegetables and garbage.

The feeding process of house flies is very interesting and somewhat nauseating. Since house flies have “sponging” mouthparts, they must liquefy their food because they cannot chew. So, house flies use their saliva to make liquids from solids and then “lap up” the liquefied food. The house fly adult lands on something they want to consume, regurgitates their saliva, and then proceeds to mix the saliva with the food until forming a liquid.

At this point, house flies use their sponge-like mouthparts to pick up the liquid and eat. Also, flies taste foods with their feet, which is the reason they may crawl around on something before deciding to eat it or select something else. This general explanation of the house fly’s feeding habits should make one think twice before eating something that a house fly has landed on, especially since house flies are able to mechanically transmit numerous diseases.


House fly adults eat milk, sugar, blood, feces and rotting foods like fruits and vegetables. The larvae obviously eat whatever organic matter they develop in, and that includes garbage, dead animal flesh, feces, and various sorts of decaying organic matter. They can eat only liquids or foods they liquefy with their saliva.


House flies live in close proximity to humans and their animals. Because house fly larvae develop in human garbage and animal feces, they will inhabit virtually any locations where their larvae can find a food source.


House flies go through complete metamorphosis, which means they have four developmental stages – egg, larva, pupa and adult. The life cycle begins with a fertile female fly laying eggs on a source of food for the larvae. Eggs quickly hatch and the larval stage (maggot) emerges in only about 8-20 hours when the environmental conditions are good. As the larvae feed, they continue to grow and develop and will leave the source of food to find a protected, dry place close by to pupate. The life cycle of house flies can be as few as 7-10 days if conditions are very good and perhaps as much as about 60 days when the weather is cooler and less conducive to rapid development. House fly adults live from as few as 15 days to as many as 60 days. Depending upon climatic regions, house flies complete as few as 10 generations to as many as 20 generations per year.


Observing adult, larval or pupal stage house flies is the obvious indicator of house flies. A much less obvious sign is the presence of small dark dots that look somewhat like grains of pepper. These marks are evidence of fecal droppings left behind by house adults.


House fly prevention first starts by reducing or outright eliminating the sources of food that larvae consume. So, sanitation, cleanliness and removal of anything that larvae will feed upon are the most important to prevent house flies.

Keeping flies from gaining access inside homes or other buildings is also important. So, keep doors and windows closed and tightly screened, and ensure that trash containers are clean and covered. Since house fly larvae do require some moisture, keeping potential fly breeding locations dry also helps.


If necessary, applying insecticide products to places where house flies develop and to surfaces where adults rest are acceptable control methods. Of course, anytime one uses a control product, the applicator must strictly follow the product’s label instructions. Also, using indoor misters, fly strips and commercially available fly traps are helpful.