Flies in Southwestern Ontario

Cluster Flies

Cluster flies are seasonal pests commonly found in homes and other buildings throughout Ontario. They are generally larger, darker, and slower-moving than house flies and may have fine golden hairs on the upper part of the body.

Unlike house flies and stable flies, cluster flies are not associated with garbage, food waste, manure, or poor sanitation. Their larvae develop in the soil as parasites of earthworms.

Adult cluster flies begin seeking protected shelter as temperatures cool in late summer and fall. They may enter buildings through small gaps around windows, doors, siding, soffits, rooflines, utility openings, and other exterior features.

Once inside, they gather in protected spaces such as attics, wall voids, upper rooms, and areas around windows. Warm, sunny weather can cause them to become active, even during the winter.

Cluster flies do not normally reproduce indoors, bite people, damage structures, or infest food. However, they can become a significant nuisance when large numbers gather inside a building.

Possible signs include:

Large, slow-moving flies near windows
Groups of flies gathering on sunny exterior walls
Indoor activity during warm fall or winter days
Flies appearing in attics or upper-storey rooms
Large numbers emerging in early spring
Similar activity returning each year

Because cluster flies are seasonal and often enter buildings before they are noticed indoors, the timing of an assessment can be important.

Signs of Cluster Flies

House Flies

House flies are common around homes, farms, restaurants, food businesses, waste areas, and commercial properties. They are usually grey, with darker lines on the upper body, and tend to move more quickly than cluster flies.

House flies develop in moist, decaying organic material. Potential breeding environments may include:

Garbage and food waste
Animal manure
Compost
Spoiled feed
Wet bedding
Organic debris
Waste containers and dumpsters

Populations can increase quickly during warm weather when suitable material remains available.

House flies frequently travel between waste, food, counters, equipment, and other surfaces. Their presence can therefore be a concern in kitchens, restaurants, livestock facilities, food-processing environments, and other areas where sanitation is important.

Signs of House Flies

Common signs include:

Flies gathering around windows and doors
Activity near waste, compost, manure, or feed
Flies around kitchens or food-handling areas
Dark spotting on walls, ceilings, windows, or fixtures
Larvae developing in organic material
Rapidly increasing activity during warm weather

Persistent house fly activity may indicate a breeding source on or near the property. An inspection can help determine where the problem is developing and what conditions may be supporting it.

Stable Flies

Stable flies are biting flies commonly associated with farms, barns, livestock facilities, and rural properties. They resemble house flies but have a noticeable pointed mouthpart extending from the head.

Both male and female stable flies feed on blood. They commonly bite cattle, horses, and other animals, but they may also bite people and pets. Bites often occur around the lower legs and ankles and can be painful.

Stable flies may develop in damp mixtures of decaying plant material and animal waste.

Possible breeding environments include:

Wet straw or bedding
Manure mixed with hay or feed
Spoiled silage
Grass clippings
Damp organic debris
Material collecting around feeders
Poorly drained livestock areas

Heavy stable fly activity can interfere with the comfort and normal behaviour of livestock. Animals may stamp their feet, flick their tails, bunch together, kick, or avoid affected areas.

Signs of Stable Flies

Possible signs include:

Painful bites around the legs or ankles
Flies resting on barn walls, fencing, posts, or equipment
Livestock stamping, kicking, or bunching together
Increased activity near damp bedding or spoiled feed
Flies gathering around livestock areas
Continued biting activity despite efforts to manage ordinary house flies

House flies and stable flies can appear similar from a distance. Professional identification can help clarify which type is present and what site conditions should be examined.

Why Flies Become a Problem

Fly activity may be connected to seasonal movement, access into a building, or suitable breeding material around the property.

Contributing conditions can include:

Gaps around windows, doors, siding, or rooflines
Damaged or poorly fitted screens
Accessible garbage or food waste
Accumulated manure
Wet bedding
Spoiled feed or silage
Damp organic debris
Poor drainage
Standing moisture
Frequently opened exterior doors

The conditions contributing to a fly problem vary by species and property. This is why proper identification and an onsite assessment are important before a control plan is recommended.

Reducing Fly Activity Around Your Property

Property owners can help make homes, farms, and businesses less favourable to flies by addressing common food, moisture, breeding, and entry sources.

Helpful steps may include:

Keeping garbage in tightly closed containers
Cleaning waste and recycling containers regularly
Removing food spills and waste promptly
Managing manure and wet bedding
Cleaning up spoiled feed or silage
Repairing leaks and reducing excess moisture
Improving drainage where practical
Removing damp organic debris
Repairing damaged window and door screens
Keeping exterior doors closed when possible
Addressing visible gaps around the exterior of the building

These measures may help reduce fly pressure, but established or recurring activity may still require professional assessment.

Need Help With a Fly Problem?

Whether flies are gathering indoors, affecting livestock, or creating concerns around your business, Rural Routes Pest Control can help identify the issue and recommend an appropriate plan based on an onsite assessment.

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