State University Extension
Home Maintenance And Repair - 01500591
Cluster flies are large, black, bumbling flies that can invade homes in
fall and become a nuisance throughout the winter and following
spring. They look like house flies; however, they are slightly larger.
Also, they do not have conspicuous stripes on the upper surface of the
thorax between the wings. They can be identified by the presence of
golden hairs underneath the base of the wings.
1) Cluster flies can become a nuisance because they enter buildings
in fall in search of a place to spend the winter. Often large numbers
will enter through cracks around loose fitting screens, in siding and
along eaves. They search out dark places such as wall voids and attics
and can congregate in large masses. Once in the house, if they become
warm they are attracted to light. Because of this, they may move into
living areas of the house through window casings or other wall
Cluster fly control starts with measures aimed at keeping the flies out
of dwellings. When they are seeking shelter, the flies have the habit
of congregating on the sunny sides of buildings. They gradually move
upward until they find a point of entry. Thus, all cracks in siding and
along eaves should be sealed to prevent flies from gaining entry to the
In the house, some control measures may be used. If flies have
congregated in accessible spaces such as attics, and wall voids a ready
to use pyrethroid is recommended.
For a complete listing of suggested control options for all home, yard
and garden insect pests, check with your local Extension Service, found
under local government in the phone book.
Read and follow instructions on the pesticide label.
This information comes from Michigan State University Extension
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status. Issued in furtherance of MSU Extension work, acts of May 8 and
June 30, 1914, in cooperation with the U.S. Department of Agriculture.
Thomas G. Coon, Director, MSU Extension, East Lansing,MI 48824. This
information is for educational purposes only. Reference to commercial
products or trade names does not imply endorsement by MSU Extension or
bias against those not mentioned.
information.was reviewed as
of June 2008. For more information about the contents please
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