A recent visit from some unusual flies sent me on a whirlwind of research.

After the mice visits subsided, I thought my animal messengers had done their job. Apparently the insect messengers have more to tell me.

We moved here in May of this year, rural PA, middle of the woods on a mountain top road. So its not unusual to have outdoor life visit us inside. But flies? In my bedroom and master bath? Jeez, couldn’t they have entered another part of the house?

These are not the average house flies though. They act strangely. We finally figured they came in through an opening somewhere in upper wall and found way into small crawlspace attic in bed/bath.

They love light. They only land on windows, skylights, and then soon drop dead on the floor!!

Here’s the scoop:

Cluster Flies  (Pollenia rudis)

“Homeowners are accustomed to swatting flies in the kitchen during the summer months. However, cluster flies make their debut in the autumn when they fly to the sunny sides of homes in search of protected over-wintering sites and may be found flying about inside, often in great numbers, throughout the winter. These flies are not reproducing within the structure, but become active on warm days and crawl out of wall voids and attics in a confused attempt to go back outside.

Cluster flies are thought to be native to Europe and may have found their way to North America in the ballast of ships containing soil and the cluster fly host, earthworms.


Adult cluster flies (Fig. 1) are slightly larger than the common house fly, Musca domestica . They are dull-gray with black markings and have golden-yellow hairs on the thorax, which can give the appearance of a golden sheen. The hairs are more numerous on the under side of the thorax between and near the legs.

The immature stages, egg and larva, are seldom seen as the eggs are deposited on the soil and the larva or maggots burrow into earthworms on which they feed. The maggots are cream colored and are an elongated wedge shape. As members of the fly family Calliphoridae, the blow flies, the maggots resemble other blow flies commonly found on decaying carrion.

Life History

In Pennsylvania, there may be three to four, or more, generations of cluster flies per season. The adults leave their protected over-wintering sites in the spring and will lay eggs on the soil, which contains earthworms. The hatching larvae enter earthworms, develop to their last larval stage, pupate and emerge as adults to begin the cycle anew. With the onset of autumn, the current crop of adults will seek protected over-wintering sites in such locations as hedge rows; under the bark of dead and dying trees; in the crevices of south-facing cliffs and rock faces; and within the cracks, crevices and voids in sheds, garages, barns, houses and other man-made structures.


As a nuisance pest, Pollenia rudis joins the ranks of other over-wintering pests such as the multicolored Asian lady beetle, the western conifer seed bug and the boxelder bug. Cluster flies will not damage your home. Occasionally, the flies may leave small dark-colored spots of excrement on windows and walls, but they are not known to carry any diseases of medical importance to humans. In addition to the ‘clustering’ on the sunny exterior of buildings in the fall, the flies will gather in large numbers at windows within the home on warm winter days. The flies are typically sluggish in flight and can be easily swatted or captured.

After flies have gained access to attics and wall voids – It is not advisable to use an insecticide within structures after the flies have gained access to the wall voids or attic areas. Although insecticidal dust treatments to these voids may kill thousands of flies, there is the possibility that carpet beetles will feed on the dead insects and subsequently attack woolens, stored dry goods or other natural products in the home. Although aerosol-type pyrethrum foggers will kill cluster flies that have amassed in attic areas, it will not prevent flies from emerging from wall voids. For this reason use of these materials is not considered a good solution to long-term management of the problem. Spray insecticides, directed into cracks and crevices, will not prevent the flies from emerging and is not a viable or recommended treatment.

If numerous flies are entering the living areas of the home, attempt to locate the openings where the insects gain access. Typically, flies will emerge from cracks under or behind baseboards, around window and door trim, and around exhaust fans or lights in ceilings. Seal these openings with caulk or other suitable materials to prevent the insects from crawling out.


Pesticides are poisonous. Read and follow directions and safety precautions on labels. Handle carefully and store in original labeled containers out of the reach of children, pets, and livestock. Dispose of empty containers right away, in a safe manner and place. Do not contaminate forage, streams, or ponds.”

Authored by: Steve Jacobs, Sr. Extension Associate, Revised January 2014

Penn State College of Agricultural Sciences research, extension, and resident education programs are funded in part by Pennsylvania counties, the Commonwealth of Pennsylvania, and the U.S. Department of Agriculture.

WHAT IS THIS INSECT HERE TO SAY?????  Especially at a time like this, battling breast cancer and chemotherapy, am I not experiencing enough transformation? Apparently not, according to Cluster Fly, there’s more to come!!!

The Fly Spirit Animal, By Imelda

“Your fly spirit animal is urging you to be ready to adapt to your current situation because there is prosperity and abundance soon to come. Keep your head up for better days are headed your way!

You can also expect something within you to change, and you will be experiencing a rebirth or a sense of newness in your life. You think you don’t need it, but once you have it, you’ll wonder how you even managed to survive in the past without it.

The meaning of the fly also encourages you to deal with your issues, whether you like it or not. Like the fly that transforms and adapts to even the harshest environments, you are being called to turn what seems like waste into something valuable.”

My spirit is renewed – even a fly infestation can be life enhancing. 

Image: The photo of young boy soaring through the air by his dad, Alan Lawrence, “who said the project is a way for him to prove to the world that even kids with Down syndrome, like his son William, can live magical lives.” (