The house fly can be classed under two headings. It is a generic term that applies to the common house fly, the lesser house fly and fruit flies, all of whom may enter a dwelling. It can also refer specifically to the common house fly, musca domestica Linnaeus.

The common house fly is distributed throughout the world and is a very successful breed. Its success can be attributed to a number of factors including its adaptability and resourcefulness. Although known as a house fly, the musca domestica Linnaeus can be found anywhere where there is manure or soft or decaying foodstuffs.

The amount of house flies at any given time is largely governed by temperature.