Flies in the family Sarchophagidae are the “Flesh Flies,” so-called because many species lay their eggs in open wounds. Flesh flies don’t often enter houses of food handling establishments in large numbers.
The female flesh fly lays her eggs on meat scraps or on dog excrement. They may be frequent in dog runs.
Forensic entomologists use the larvae of flesh flies collected at the site where a murder victim is found to help pinpoint the time of death.
Flesh Fly Identification
Flesh flies are medium to large sized flies and usually have three dark thoracic stripes and mottled abdomens. Many of the common species have a red tip on the abdomen.
Though some species may be smaller than house flies, most flesh flies are about 1/3 to 1/2 inch long.
Due to their markings and coloration, sometimes House Flies are confused with Flesh Flies. Flesh flies are larger than house flies. Flesh flies have a checkerboard pattern on top of their abdomen and are gray in color.
Flesh Fly Biology
Once the eggs have been laid on a suitable breeding material, the larvae hatch out from the eggs and burrow under the surface. It is not uncommon to encounter the body of a dead mouse, for example, whose body writhes and wiggles as the maggots move about inside while feeding. After growing to maturity within a few days, the larvae crawl out of the breeding material to pupate. The larvae may crawl many feet away from a breeding source inside buildings; outdoors they generally crawl only a short distance before burrowing into the soil to pupate. The adult flies begin emerging several days later. Flesh flies retain their eggs within the body of the female until they are ready to hatch. The larvae are deposited directly onto the food that the immature will be eating.
The life cycle for the common species can be completed in eight to 21 days. The preferred breeding media around residences are decayed flesh, spoiling meat, and manure. Usually garbage can meat scraps and dog food left outside are abundant sources of flesh fly breeding. Flesh flies can breed in dead rodents and birds in attics or wall voids of houses.
Adult flies do not bite but feed on a wide range of liquid substances. Most larvae infest wounds, carrion or excrement. The larvae of some species of flesh flies are beneficial in that they prey on eggs, nymphs or larvae of more harmful insects. Lesser house fly larvae, blow fly larvae, and grasshopper nymphs are common hosts of flesh flies.
Flesh fly life histories vary with species and location. They over winter as pupae in temperate climates. Rarely very numerous, the flies emerge in spring and mate. Eggs are laid only under very unusual circumstances. As a rule, eggs hatch within the body of the adult. Females of most species deposit 20 to 40 larvae directly onto the host or substitute. As many as 325 larvae have been known to be born by a single female. Flesh fly maggots feed for three or four days and develop though three instars. Soon afterward, these mature maggots enter the pupae stage. Adult flies emerge in ten to 14 days; the life cycle is repeated. Several generations are produced each year.
Flesh Fly Inspection
Flesh flies generally do not infest structures in large numbers or with any regularity. Flesh flies will be attracted to buildings by odors emitting from the dumpster or the building itself. Rendering plants and meat processing facilities may attract more flesh flies than other types of facilities such as a hotel or hospital. Occasionally, one or more flesh flies will manage to enter the building. If this is the case, try to determine if a breeding source is located near the building and how flies might be entering the structure. Accumulation of garbage under a dumpster is a common breeding source for flesh flies near buildings. Occasionally, a large number of flesh flies will suddenly appear in a particular area inside a building. These flies are most likely breeding inside a dead rodent or bird inside a wall, false ceiling, or the attic. Occasionally, mature maggots may be found crawling about. These larvae have left the breeding source in search of a place to pupate. Most infestations of flesh flies can be attributed to garbage or rodent carcasses found in or underneath trash dumpsters. Most infestations of indoor Flesh Flies are small in numbers and can be traced to dumpsters, meat processing plants or rendering facilities located nearby. If large numbers of these pests are found indoors, it can usually be attributed to a dead animal such as a rodent or bird. Backtracking the paths of fly maggots will many times help locate the carcass or source of indoor Flesh Fly infestations. If fly maggots are located in light fixtures, an inspection of the attic and nearby wall voids might be necessary.