HOUSE BOAT. In its simplest form a house boat consists of a cabin of one or two rooms built on a flat bottom scow, draw ing only from 12 to 24 in. of water, and usually with a platform or porch at either end. In the East wherever water is found the house boat is an established institution as the residence for a number of inhabitants, owing to overcrowding. In the West such boats are found in great numbers on small rivers or streams especially where there is good fishing and shooting, on the shallow waters of inland lakes and on the numerous harbours along the coasts. When used as summer homes, house boats have been developed into quite elaborate craft, having four or more rooms, with a broad porch or veranda on top protected by awnings, the hull construction still retaining the characteristics of a flat bot tomed scow, having great stability. In this form the boats have no motive power and have to be towed from place to place when it is desired to change their position. With the introduction of the internal combustion engine, power house boats have been de veloped and have become very popular by reason of the facts that they can be moved from place to place easily and com bine the roominess and comfort of the house boat with the convenience of the power cruiser. They are for the most part screw driven, and range in length from 45 to 1 oo ft. or over. Being of shallow draft the living quarters are in the super structure, with large windows giving plenty of light and ventila tion, and they have broad decks, making ideal summer homes. In the United States many of these power house boats are used in northern waters during the summer months and taken South under their own power, to be used in Florida or along the Gulf coast during the winter months. (H. L. ST.) (Musca domestica), a two-winged insect be longing to the family Muscidae of the order Diptera (q.v.), com mon in dwellings and practically cosmopolitan, being found where ever man has established himself. It is most abundant during the hotter parts of the year, and in Europe and North America attains its greatest numbers from July to September. Its chief breeding place is in accumulations of horse manure, but it also utilizes various kinds of fermenting animal and vegetable matter, including the contents of ash bins, etc., where the eggs are laid and the larval life is passed. A single female usually lays 600 1,000 eggs in her life-time, but higher numbers are known. The cycle, from egg to fly, varies in different parts of the world with temperature and other factors. Under favourable conditions it may only occupy io or 12 days, and there is opportunity for a number of successive generations in a season. During the winter house-flies disappear : a few, however, maintain themselves in warm buildings, and perhaps continue to reproduce, but further information is needed on this point. The house-fly has an im portant bearing upon human welfare since it acts as a carrier of the germs of summer diarrhoea, typhoid and other diseases ; con sequently its suppression is of great significance in public health. The omnivorous nature of its diet contributes to its efficacy as a germ-carrier. The treatment or abolition of all material wherein it can breed and the destruction of the flies by adhesive fly-papers, poison baits or other means is very important.
See C. G. Hewitt, The House-fly (1914) ; also W. B. Herms, Medical and Veterinary Entomology (1923). (A. D. I.)