False Stable Fly Muscina stabulans (Fallen), Muscidae, DIPTERA


Adult -- Darker and more robust than a house fly, the false stable fly has four dark stripes on its thorax and a pale spot on the top of the thorax near the abdomen. The abdomen may be entirely black or reddish on the sides, and parts of the legs are yellow. This nonbiting species averages 8 mm in length.

Egg -- No available description.

Larva -- This tough-skinned maggot develops through three instars. White and about 1.5 mm long when newly hatched, it gradually matures into a grayish or cream-colored larva 12 to 18 mm long and 5 to 6 mm wide.

Pupa -- No available description.


Distribution -- Practically cosmopolitan, the false stable fly occurs in North America from Alaska to Newfoundland and south to Georgia and Arizona. Common in the immediate vicinity of human settlements, this species inhabits outdoor toilets, orchards, and vineyards.

Feeding Habits -- Adult flies of this species do not bite. False stable flies feed rather on various liquids including nectar, tree sap, decaying fruits, and aphid honeydew. Early instar larvae feed on decaying organic matter, particularly excrement and rotting cruciferous plants. As larvae near maturity, they become predatory on house fly larvae.

Damage -- False stable flies are capable of transmitting dysentery to man and brucellosis and mastitis to animals. Such diseases are transmitted by fly contact with livestock feed or man's food. In addition, cases of intestinal pseudomyiasis (infestation by fly larvae) have been known to result from consumption of food contaminated with fly eggs.

Life History -- Practically no biological studies of this insect have been undertaken in North America. In Europe, this species is known to overwinter as pupae or occasionally as prepupae. Soon after female flies emerge in the spring, they begin scattering 140 to 200 eggs over piles of manure, decaying plant material or other suitable food substances. Developing faster at warm temperatures, larvae feed for 15 to 25 days. They then pupate and the life cycle is repeated. Several generations are produced each summer.


Sanitation does much toward reducing the false stable fly population. The removal or burial of accumulated manure or decaying plant material eliminates favored breeding sites.