What are stable flies?

The stable fly (Stomoxys calcitrans), is also sometimes called the “biting fly” or “dog fly,” is a common fly which mainly bites horses and catlle , but also humans, dogs and pigs. Stable flies are difficult to distinguish from house flies, except that stable flies have a bayonetlike mouthpart (proboscis) protruding from the front of the head. See the picture opposite which shows the stable fly (top) and house/bush fly (bottom).

Adult stable flies (of both sexes) feed during the day, generally in the early morning and late afternoon. The female fly requires blood before she is able to lay eggs.

The life cycle of a stable fly

Stable flies typically appear during midspring, they become severe during summer, and numbers tend to decrease in late summer. In prime breeding times stable flies can develop from egg to adult in just 2 weeks. Females lay over 100 eggs per batch and she may lay five batches in her lifetime, so there is the potential for rapid increases in fly numbers in a short period of time.

Where do stable flies breed?

The larvae or maggots of stable flies can breed in animal and poultry manures (particularly when mixed with organic matter), horse stables, decaying vegetable matter, open compost heaps and grass clippings.

How can I stop stable flies breeding on my property?

The most effective for reducing stable fly numbers is to eliminate their breeding sources.

• Moist grass clippings should be spread thinly to dry.
• Maintain compost piles to promote rapid decomposition of organic matter, this generates heat and makes the pile unsuitable to fly larvae.
• Pest/Fly proof the outside of a structure eg: compost to prevent flies from entering. This technique includes caulking cracks, weatherstripping doors, and installing screens.

What should I do if I have stable flies?

Contact your local shire. Click here for more details on what to do.

Acknowledgements

Environmental Health Guide, EHS57, “Stable Fly”, Health Department of Western Australia. Click here to download the full brochure.