Face Fly

family: muscidae
species: musca autumnalis
common names: face fly, cluster fly, attic fly
hosts: feeds on earthworm contents
notes:

Agriculture and Agri-Food Canada Insect Identification Sheet No. 71 August 1981

Face Fly

Musca autumnalis (De Geer)

The face fly is believed to have been introduced into Canada in 1952 in Nova Scotia. It has since become a pest of cattle across Canada.

Injury:

The adults feed upon secretions from the eyes, nose and lips. They are bloodsuckers — although unable to pierce the skin, they are attracted to any wound or sore on cattle. The flies greatly distress cattle, resulting in less grazing time, lower weight gain and reduced milk and butterfat production. Inflammation to the point of blindness can result from flies feeding around the eyes.

Life History:

Face flies overwinter as adults. The females lay their eggs in cow dung or other excrement, where they hatch into larvae and feed. Larvae are off-white, reaching a length of 8 to 19 mm at maturity. They pupate in the ground, the pupa being whitish. Adults resemble the common housefly, though slightly larger. Females have a silvery stripe near the eyes instead of the gold strip of houseflies. Adult face flies prefer moist shaded pastures and several hundred may congregate in masses on cattle. They are also frequently seen in large numbers resting on rocks or fence posts. They avoid entering barns. Adults are active from early spring to late fall. There are several generations per year in Canada.

Pest Management:

There are several repellents available to discourage the feeding activities of this pest. Contact your provincial Department of Agriculture for details.

From Harry Kendrick — Kendrick@Dartmouth.Edu>:

I agree with James Johnson, that this insect sounds like it is a "cluster fly" In New England, this is one of our common institutional and household winter pest problems. They are also somearial called "attic flies" because they are found in attics. They are particularly noticeable on warm days when they become active and find their way into living quarters, causing a nuisance. They are only using the home or building as a place to spend the winter, and do not cause damage to the building, furnishings or occupants.

To help you identify it, the cluster fly resembles the common house fly. There are no obvious distinguishing characteristics, but with the aid of magnification you will find glistening, yellow hairs lying flat on their thorax and stouter bodies, which house flies do not have. The abdomen has a checkered light and dark pattern.

The cluster fly is active outdoors in the summer, laying eggs near the openings of earthworm burrows. Upon hatching the young larva burrows into the earthworm and feeds on the contents of the earthworm until it is ready to pupate, at which time it leaves the host to form a puparium in the soil. The adult that emerges then repeats the cycle, with up to four generations being produced each summer. As the temperature drops in mid-August and up until a heavy frost, the cluster flies will seek protected areas to spend the winter. They invade attics, get under siding and around windows, and into most any crevice on the outside of buildings. Many will eventually congregate between walls and can work their way into a room through openings in the window frames and electrical fixtures. This is why you will find them in light fixtures. They are usually sluggish and make little attempt to escape, so they can easily be picked up with a vacuum cleaner.

On warm days in the Spring they will move outdoors. I've been battling these flies for at least twenty years, and have yet to fully win the battle. Some of the control measures that will help in addition to vacuuming them up are:

1. Preventive: Prevent their entrance into the building by sealing up cracks in the siding and around windows. Put screens over attic air vents, etc.
2. Chemical: Around the second or third week of August you can hire a pest control company to spray the outside of the building with a cypermethrin (Demon WP). Usually you only need to spray the three sides of the building that have sun on them for prolonged periods. Also, since they usually come in at the upper levels of the building you may not need to spray the lower levels. This spray needs to stay on the windows and building until the first heavy frost. After that, you will want to wash the windows. I understand that the wettable powder (WP) is more effective than the emulsifiable concentrate(EC). Also, in remote areas such as attics or above ceilings you may find the Vapona Pest Strips to be effective. However, Do not hang these in kitchens, restaurants, or areas where food is prepared. Also, Do not use these strips in nurseries or rooms where infants, ill or aged persons are confined.
3. Electric: Inside the building, we also use the new "Vector" Fly Systems to trap the flies that are able to enter the building. These are like a fancy glue board, but are quite effective in trapping the flies, and they can be used in restaurants, schools, hospitals, nursing homes, etc. Much of this information was detailed in a University of New Hampshire Bulletin on Cluster Flies. However many of the comments are due to my personal experience of doing battle with this troublesome pest.
   

Harry Kendrick Dartmouth — Hitchcock Med Ctr. Lebanon, N.H. 03756

H_Kendrick@Dartmouth.edu

Subject: Re: house flies

In a message dated 96-04-09 07:44:16 EDT, you write: It's been a long time since my Extension Service days, but I believe that the spacing between the eyes is a type of sexual dimorphism -- males have large, (narrowly spaced) eyes and females have smaller (widely spaced) eyes. Given the time of year and the circumstances I have to wonder if these flies are actually cluster flies, Pollenia rudis, (which commonly overwinter in buildings). They look similar to house flies but lack the pronounced thoracic striping and have a patch of golden hairs on the thorax beneath the wings. Face flies are also encountered in buildings in some areas.

Gary Dunn Young Entomologists' Society YESbugs@aol.com

Randy: You probably are dealing with face flies, Musca autumnalis, rather than house flies. Face fly was introduced from Europe/Africa? into North America in the 1950s and it extends today from coast to coast, but is restricted from the southern tier of states (in the US). This fly is part of the complex of "attic flies" aggregating in attics of farm or rural buildings; they are also called cluster flies (although the true cluster fly is another species) because of their clustering behavior. They enter adult, reproductive diapause in late fall; and aggregate in the attics, somearial reaching numbers into the thousands. They appear to use the same place year after year, and even buildings located several miles from their breeding sites, cow pats.

During the winter, any day that the sun shines and warms up their hibernacula, they become active and "try" to leave their places, usually ending up in the living quarters, becoming a nuisance. At this time they are noticed and misidentified as house flies. They will emerge from their hibernacula in early spring. We have been conducting studies on their behavior, physiology, and survival during diapause and have found out that they often leave their hibernacula and return to these places in late afternoon.

So, during the winter they feed on something (we have detected sugars). Male face flies, similar to other muscoid flies, have holoptic eyes, that is, almost contiguous; whereas female eyes are dichoptic, that is, widely separated. The eye extension varies with the species. Eyes of male face flies are almost contiguous (almost touching), whereas the eyes of male house flies are considerably more separated (separated by at least 1/3 the width of each eye). Eyes of females of both species are widely separated. I hope this is of some help. If you have some specimens of these flies and would like us to determine whether they are face flies, please send me some specimens.

Sorry I can not be of much help with the second question, but I have always though the squama was somehow involved in the flight mechanism.

Regards, Alberto.

Alberto B. Broce, Ph.D. + Kansas State
University + Department of Entomology
voice: 913-532-4745 + West Waters Hall FAX: 913-532-6232
+ Manhattan, KS 66506 USA + e-mail:
abroce@oz.oznet.ksu.edu +

I have seen a suggestion that the calypters function to mimic the sounds produced by bees and wasps. The posterior calypter somearial covers the halteres so I suppose can increase the buzzing sounds.

Eileen Van Tassell
22301evt@msu.edu Department of Entomology
Michigan State University East
Lansing, MI 48824-115