There are 18 000 or so species of true flies (sometimes called calyptrate Diptera), and this vast number includes several medically important species in the families Glossinidae (Chapter 8), Muscidae and Fanniidae, the last two of which are described in this chapter.

The Muscidae contains about 4200 species of flies in 170 genera. The medically most important are the common house-fly (Musca domestica), the greater house-fly (Muscina stabulans) and the stable-fly (Stomoxys calcitrans), all having a more or less worldwide distribution. House-flies can be vectors of helminths, faecal bacteria, protozoans and viruses, resulting in the spread of enteric diseases (e.g. dysenteries and typhoids). The stable-fly can cause a biting nuisance.

The family Fanniidae comprises about 280 species in four genera but only species in the genus Fannia, such as F. canicularis (lesser house-fly) and F. scalaris (latrine fly), are of medical importance, and like house-flies they can transmit various pathogens to humans.

The common house-fly (Musca domestica)

External morphology

There are about 70 species of flies in the genus Musca. The most common is M. domestica, the house-fly, which is almost worldwide but is least common in Africa, where it is largely replaced by two subspecies (M. domestica curviforceps and M. domestica calleva). Other important species are (1) the bazaar-fly (Musca sorbens), which can be a great nuisance in Africa, Asia and the Pacific; (2) the notorious troublesome bush-fly of Australia, namely M. vetustissima; and (3) the face-fly (M. autumnalis), which is a pest in both the Old and New Worlds.