|Cluster Fly biology, identification, image, control tips and
products for eliminating cluster flies.
The Cluster Fly is listed in our category of Biting & Nuisance flies, but is the only one of the group
which does not have a metallic coloration; they are dark gray in color. These
medium-sized insects are 1/4 inch to 3/8 inch in length. Cluster flies are
distinguished from other flies by the presence of golden yellow hairs on the front, top of
the thorax. Another noticeable feature of the Cluster Fly is the way its wings are
held flat over its back while resting; the wing tips overlap when held in this
position. This fly is often mistaken for a house fly or
a face fly.
Cluster fly females lay their eggs singly in
cracks in the soil; the larvae emerge in three days and begin to seek out their food
source: earthworms. After burrowing into the earthworm, the larvae feed for about
three weeks before pupating. The adult Cluster Fly emerges from its pupa after 12 to
14 days. The adult flies ( of which there 3 to 4 generations per year) feed on
Homeowners are often bothered by the appearance of sluggish flies in their homes in
late winter and early spring. These flies are not breeding in the home but will
become quite a nuisance if not controlled. These flying pests are parasites of
earthworms. The more abundant earthworms are around a home, the more likely it is that
cluster flies will become an indoor pest. Earthworms are most abundant around places
where manure has been piled or stored and are common in grassy areas where the soil has
In the fall, adults search for a protected overwintering site: an attic, loft, loose bark,
holes in trees, or other crevices. Siding without cracks, crevices or other
protected areas are usually fly free, but white loose-fitting vinyl or aluminum siding
will attract nuisance flies.
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Cluster flies, face flies and blow
flies are difficult to control once they have gained access to homes because they
hibernate in wall voids and other inaccessible places.
- Exclusion: Close and seal as many openings as possible through which
the flies can enter. This procedure is time consuming and may require a dedicated
long term effort. Window screens offer no protection from Cluster flies because they
crawl into the home through small openings in the walls of the building. These same
overwintering flies get into rooms during the winter and spring months entering through
window pulley holes, around the baseboards and through other small openings in walls.
A thorough inspection for locating and eliminating all possible entry points is a
must, but will not guarantee success. For best control, use chemical sprays with
your exclusion methods.
- Surface Spray: Use a compressed air sprayer (Chapin Sprayer) to apply a surface spray to surfaces in attics, basements,
closets, store rooms and other areas where the flies congregate. These sprays also
are effective if applied to the outside of the house in the fall when the flies collect in
these areas before entering the home. Pay special attention to the areas beneath the eaves
and around the windows and other areas where flies are likely to seek entry.
- Crack and Crevice Treatment: Using a pyrethrin aerosol for treating cracks and
crevices will compliment your surface spray.
This method is only necessary if there are areas to be treated that you cannot
properly treat with a surface spray.
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Cynoff WP is the best surface spray for
- The first step in Cluster Fly elimination is to seal or eliminate
all possible entry points.
- Use a good surface spray
on all areas where cluster flies congregate, hibernate or enter a structure.
Cyper WP is the best surface spray for nuisance
flies. When used according to label instructions, this product is safe
around children and pets, and also gives a very long residual protection against a wide
variety of pests -- with no odor. For ordering information and product description,
go to our Fly Control Products page.
- If necessary, use a crack and crevice aerosol for hard to reach
areas. Delta Dust is a good crack and crevice tool.
Professional Pest Control Products
Pensacola, Florida 32526
Call us, between 8:30 &
4:30 weekdays, Central Time
In the United States: 1-800-434-4555
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