Facts About Large Flies (“House Flies”)

Large flies, also known as filth flies, include houseflies, bottle/blow flies and flesh flies. Understanding the biology and behavior of these common types of large flies can help with fly prevention in your facility. 

Biology & Behavior

Flies complete their life cycle from larvae to adult in just 8 to 12 days. 
A female fly can lay as many as 500 eggs in her lifetime.
Adult flies focus attention on critical life activities such as finding food and water, reproductive activity, and finding suitable breeding material for egg laying. Once a good breeding and feeding site has been found they will remain in the area. 
The common housefly is known to carry over 200 different pathogens and can carry 1.9 million bacteria on its body.
Temperatures above 70°F/21ºC stimulate fly emergence as heat causes rapid decomposition of vegetation and other organic matter, providing ample food for flies and their larvae. Temperatures below 60°F/15ºC will significantly reduce fly activity.
Large flies such as houseflies and blow/bottle flies are often called Filth Flies because they feed and breed in filth -- dumpsters, garbage, manure, decaying vegetation. 
House flies will often regurgitate and excrete on the surfaces they land, potentially transmitting at least 65 diseases to humans, including typhoid fever, dysentery, cholera, tuberculosis, and Helicobacter pylori (a major cause of stomach ulcers in humans), and Salmonella bacteria.
Large flies can travel a mile or more to find suitable food and breeding material. 



Common Large Flies

Flesh Fly

Flesh Fly

Many species in this group do not lay eggs, rather the female flies deposit live larvae on or near the breeding source. Flesh flies develop in decaying flesh and spoiling meat.

House Fly

The most common of the large flies, breed outdoors in decaying organic material and manure, and can harbor over 200 different pathogens. Houseflies lay their eggs on warm, moist, decaying organic material. Main breeding sites include manure, dumpsters, garbage and decaying vegetation, where bacteria and other microorganisms thrive.

Flesh Fly.

Blow/Bottle Fly

Distinguished by its metallic appearance, this fly breeds outdoors in decaying vegetation and carrion, and feeds on sewage and feces. Bottle and blow flies are often seen near meat processing plants and slaughter houses. Although bottle and blow flies lay eggs on many types of decaying organic matter, they prefer meat or dead animals.

More Resources

Fly on toast.

Large Flies and Food Safety

Large flies including houseflies, bottle or blow flies and flesh flies are also called “filth flies” because they breed in filth such as manure, human excreta, dumpsters, garbage, and decaying vegetation, causing a food safety risk.

Man cleaning and sanitizing a table.

How to Prevent Large Fly Problems

To protect your business from the health risk posed by large flies such as houseflies and bottle/blow flies, there are steps you and your pest management provider can take to minimise food safety risks. 

Image of the outside-in approach.

Benefit of Outside-in Approach

Implementing a comprehensive programme utilizing an Outside-In Approach can greatly improve your efforts towards large fly prevention in your facility.