Adult face flies look much like house flies. They are about 6-8 mm in length and have four dark stripes on top of their gray-colored thorax. Females look almost identical to males except they have yellow coloration on the front portion of their abdomen.
Behavior, Diet & Habit
Face flies are cattle pests in the warm weather months, but migrate into the walls, attics or ceilings of barns or other buildings that provide a protected place to overwinter. As the weather warms in late winter and early spring, the adult flies move outdoors or may become active indoors. Face flies, problems for cattle and to a lesser degree horses, are present in the field throughout the summer with populations usually peaking in late July and August.
Face flies go through four life stages: egg, larvae (grub), pupae (cocoon) and adult. They will complete one entire life cycle in as little as 15-25 days. Female face flies lay their eggs only in the manure of grass-fed cattle that is less than one hour old. Interestingly, face flies seem to avoid other feces for egg laying. Eggs hatch within the manure pile and larvae develop under the drier manure crust. When the larvae mature, they crawl into the soil close to the manure pile and develop into pupae. After about one week, adult flies emerge from the soil.
Although adult face flies don’t bite, their feeding habits make them troubling to cattle. Face flies feed on secretions from the eyes and noses of large animals, and are known to use their rasping, sponging mouthpart to stimulate tear flow from the animal’s eyes so they can lap up the secretions from eyes as well as nasal discharges, saliva, or blood oozing from wounds. Face flies spend most of their time away from their host animals, resting on plants, fence posts, or other protective objects. Male face flies spend most of their time feeding on plant nectar near the cattle or horse pasture rather than on fluids, saliva or blood.
Beyond irritating cattle, this behavior also can result in the transmission of diseases and reduced food and feed consumption, all of which can result in less milk and weight production.
The reproductive potential of face flies is very high since they can complete one generation in such a short time.
Signs Of A Face Fly Infestation
The presence of face flies either on or around cattle or the occurrence of face flies in their overwintering sites are the most obvious signs of an infestation.
Face flies are found over southern Canada and most of the more temperate portions of the United States.
Face flies are one of the most difficult pasture pests to control since they are on cattle only for short periods of time during the day and stay mostly on the head, which is difficult to treat with conventional insecticide applications. Therefore, the most effective methods of control are treatments where the livestock are forced to come in contact with an insecticide on a daily basis. Devices such as dust bags, livestock oilers, or an insecticide impregnated ear tag will be effective if used on both adult and young animals. The best advice for face fly control is to seek out your veterinarian or local extension agent for recommendations.
In addition to being very annoying to cattle, face flies play a role in the transmission of bovine pinkeye and secondary bacterial infections of bite wounds.