Rev. sci. tech. Off int. Epiz., 1994,13 (4), 1159-1173  Non-biting Muscidae and control methods  G. THOMAS * and J.B. JESPERSEN **  Summary: Many non-biting muscids (filth flies) are characterised by the habit of visiting manure or rotting organic material to feed and/or oviposit. As these flies also often have close associations with human beings, as well as human habitations and domestic animals, they are potentially both a nuisance and a contributory factor in the transmission of diseases. The authors examine the biology, economic importance and control of four of the most important non- biting muscids: - housefly, Musca domestica; - face fly, Musca autumnalis; - Australian bush fly, Musca vetustissima; - sheep head fly, Hydrotaea irritans. KEYWORDS: Biology - Bush fly - Control - Disease transmission - Economic importance - Face fly - Head fly - Housefly. INTRODUCTION  Non-biting flies in the family Muscidae belong to the suborder Cyclorrhaph (Diptera) and are characterised by antennae having three segments, of which the last bears a bristle called the arista. Many of these flies breed in decaying organic materials (e.g. manure), and are therefore also known as filth flies. Flies which live in close association with humans (e.g. Musca domestica) are termed synanthropic, while flies associated with cattle (e.g. M. autumnalis and M. vetustissima) are termed symbovine. Flies highly dependent on human and animal habitation (e.g. M. domestica) are said to be endophilic. Flies which require a living host to complete their life cycle are referred to as obligate ectoparasites (e.g. Hydrotaea irritans), while others are termed facultative parasites (e.g. M. domestica). If the fly transmits pathogens from one animal to another, it can function as a vector. When development of the pathogen within the vector is essential for successful transmission, this is termed biological transmission (e.g. the transmission of Parafilaria bovicola by M. autumnalis), whereas mechanical transmission is said to occur if the fly simply functions as a carrier of the pathogen(s) (e.g. the bacteria causing summer mastitis and H. irritans). In addition to their vector status, many non-biting flies are important as a nuisance to farm animals and humans living nearby. Four of the most important of these species will be described below, although it should be noted that many other non-biting muscids are of veterinary importance. * Institute for Animal Science and Health, Head Office, Edelhertweg 15, P.O. Box 65,  NL-8200 AB Lelystad, The Netherlands.  ** Danish Pest Infestation Laboratory, Skovbrynct 14,2800 Lyngby, Denmark.