KINGDOM: Animalia | PHYLUM: Arthropoda | CLASS: Insecta | ORDER :Diptera
FAMILIES: Muscidae (house flies), Calliphoridae (blow flies), Sarcophagidae (flesh flies), Tachinidae (tachinid flies)

Although it can be difficult to determine the family to which any one of these flies belongs, there are common characteristics exhibited by each family which are highlighted in the Common Types section below.  These characteristics can aid in identification, but a microscope is essential for accurate identification.  For technical details on identifying these flies, consult an accurate guide to insect taxonomy, such as:
Peterson Field Guide to Insects: Borror and White
Introduction To The Study of Insects: Borror, Triplehorn, and Johnson

Like all true flies (order Diptera), house flies and their relatives do not have chewing mouthparts.  Instead, most flies in these 4 families have sponging mouthparts which are used to absorb liquids, such as nectar.  Others, like stable flies, have piercing mouthparts used to suck blood.  Like all insects, flies have 6 legs, 3 body regions (head, thorax, and abdomen) and 2 antennae.

Except for a few species whose larvae are parasitic on other insects, larvae from the "house fly" families are legless, soft-bodied maggots.  Maggots are most commonly found in carrion or in animal waste.

Like all flies, house flies and their relatives have complete metamorphosis with egg, larval, pupal, and adult stages.  The larvae are legless and wormlike.  Winged adults are active outdoors during warm months, and indoors all year round.

Their are many important pests in the families Muscidae, Calliphoridae, and Sarcophagidae.  Flies in all of these families are a nuisance when they get into homes and when they occasionally spread diseases to humans.  Read about the control of home-invading flies in our ENTFact:
www.uky.edu/Agriculture/Entomology/entfacts/struct/ef624.htm

The family Muscidae also contains Face Flies, Horn Flies, and Stable Flies.  These flies harm livestock by causing irritation and spreading disease.  Read about these livestock pests in the following ENTFacts:
    Face Flies and Pink Eye
    Horn Flies and Cattle

Some flies in the families Calliphoridae and Sarcophagidae are capable of infecting open wounds on humans and animals, a condition known as myiasis.  Myiasis in humans is rare in the United States, but commonly occurs in tropical regions.

THE HOUSE FLY
FAMILY: Muscidae | GENUS and SPECIES: Musca domestica
The House Fly, Musca domestica, pictured below, is one of the most common members of the family Muscidae, and one of the most common flies found in homes.  It is about 1/4" long, and gray with 4 black stripes on the thorax.  The house fly doesn't bite, unlike face flies, stable flies, and horn flies, which are also in the family Muscidae.  Muscid flies and their maggots breed most commonly in manure.

House flies and their relatives are easy to find in Kentucky.  House flies, flesh flies, and blow flies are found year round, and are especially common in barns or other areas where animal waste is present.  Tachinid flies are common as well, but are more likely to be found in weedy areas and in agricultural crops.  None of these flies are very common during winter months.  All of these flies are good fliers, and an aerial net is needed to catch one.  They do not remain still for long, so sneaking up on one for a photograph requires much patience!  Try finding one on a cool summer morning - during these times, the fly will still be warming up its muscles, and will not be as quick to fly.

Fly maggots are common as well, but should be avoided because they can sometimes spread disease.

CSI Flies: Because blow flies are so common on carrion, their presence on human corpses often plays a part in criminal investigations. Read more about crime-solving blow flies at the Forensic Entomology Pages.

Before scientists completely understood fly biology, it was believed that maggots spontaneously appeared in decaying flesh.  Only during the 17th century was it scientifically proven that maggots appeared because of flies laying eggs in carrion.