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Blow Flies

green bottle fly picture

General Facts

Also known as bottle flies, blow flies are filth loving flies. They breed in animal carcasses or fresh wounds. In fact, forensic scientists often use blow flies as indicators for how long a body has been dead.


Adult blow flies vary in colour, ranging from metallic green, blue, bronze to black with hints of copper. They are slightly larger than house flies, measuring about 6 to 16 mm long. The pests have hairy backs and are strong fliers. Their larvae are known as maggots; they have smooth, legless, worm-like bodies and are white to yellow in colour. Pupae have reddish-brown shells.


Blow flies are common in the northern hemisphere. Because of their breeding habits, they are likely to inhabit areas near livestock or other groups of animals. These scavengers also live around garbage and excrement.


The pests feed on decaying organic matter such animal carcasses and plant matter or garbage. Immature larvae have black mouth hooks for tearing through the flesh of animals they hatch onto.

Life Cycle/Reproduction

Adult females are able to lay up to 500 eggs in clusters of 20 or more. They reproduce on dead decaying animals, open wounds in live animals, or exposed meat. Blow fly eggs develop into full-grown larvae within several days, and then enter the pupal stage for anywhere from one to three weeks.

Problems Caused by Blow Flies

Infestations often indicate and add to the unpleasantness of sewer issues in homes or decaying dead animal or garbage. People who live on or near farms may have more issues with blow flies, as they are attracted to animals or manure. In any case, the pests’ presence typically points to some kind of larger, sanitation problem.

Detection/Signs of Infestations

These pests pose little danger to humans, but can be a problem for pets. Some species of blow flies lay eggs on dead animals and even in the wounds or sores of live animals and the larvae develop inside the tissue – a condition known as myiasis. Myiasis damages animal body tissues, can affect the health and well-being of an animal and in extreme cases, it can lead to death. Pets that seem to be agitated, especially those that are older, ill, or injured, may have a blow fly infestation.

Prevention Tips

Any injured or dying wildlife that wanders onto the property can attract blow flies. Family pets with an illness or buried in the yard may entice the pests as well. Be sure to follow guidelines for burying animals properly to avoid attracting blow flies and other scavengers.


Houses with a fly infestation likely have other wildlife that is dead or dying nearby. Since wounded animals and carcasses may pose health risks to people, a sudden influx of blow flies should be a cue to do a thorough home inspection. To safely manage blow fly problems, contact the pest control experts at Orkin Canada.

Additional Information

How to Get Rid of Blow Flies