Michigan State University Extension
Home Maintenance And Repair - 01500591
06/24/03
Cluster Flies
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. (Vis. 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 openings.
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 house.
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 bulletin E-955, Cluster Flies.
This information is for educational purposes only. References
to commercial products or trade names does not imply
endorsement by MSU Extension or bias against those not
mentioned. This information becomes public property upon
publication and may be printed verbatim with credit to MSU
Extension. Reprinting cannot be used to endorse or advertise
a commercial product or company.
MSU is an affirmative-action, equal-opportunity employer. Michigan State
University Extension programs and materials are open to all without regard to race,
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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.
This file was generated from data base 02 on 02/04/08.
Data base 02 was last revised on 06/24/03.
For more information about this data base or its contents please contact
strausc@msu.edu .