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Drosophila melanogaster is a fly, distributed world wide with the exception of extremes of altitude or latitude. Its claim to fame is that, for the last 100 years or so, it has been a favourite organism for biological research, initially in the field of genetics, but latter for the investigation of fundamental problems in biology from the fields of ecology to neurobiology. Systematically, D. melanogaster belongs to the large family of Drosophilae (with over 4,000 known species), a family of acalyptrate flies. By and large members of this family are specialized to feed, as larvae, on rotting vegetable matter that is undergoing fermentation due to yeast or bacterial contamination. It is these microorganisms that constitute the food of larval Drosophila. In the laboratory, however, D. melanogaster is grown on a flour-based medium gelled with agar and seeded with baker's yeast.
D. melanogaster is a commensal of humans, a history recently reviewd by Keller . It is most commonly found in close association with human habitation, and is often found inside houses, especially in the fall where it is attracted by fruit and wine. Adults are often found drowned in a glass of wine left in a room overnight. The ecological versatility required to associate with human habitations, from the coasts of New Guinea to Manhattan, has predisposed D. melanogaster to be a very robust laboratory organism. The world-wide distribution of this fly is relatively recent, however. Its ancestral home is thought to be tropical West Africa. From there it spread to Euroasia, perhaps 6,000-10,000 years ago. It spread to the Americas only 500 or so years ago, probably on trans-Atlantic slave ships.
Although described in the scientific literature in 1830, by the German entomologist Johann Wilhelm Meigen (1764-1845) , these flies were known to the Ancient Greeks. The first experimental studies with D. melanogaster were done, just over a century ago, by F.W. Carpenter and by William Castle  in Harvard, for studies of the effects of inbreeding on fecundity. Castle's work showed that D. melanogaster was suitable for experimental work and brought it to the attention of Thomas Hunt Morgan, an embryologist at Columbia University in New York who wished to make an experimental study of evolution [see 3 for a historical accounts of the introduction of Drosophila into research and of the Morgan School]. His discovery, in 1910, of a white-eyed variant, and his demonstration that this factor showed sex-linked inheritance, was seminal to the then new field of genetics . Over the next thirty years or so, Morgan's school and colleagues established the foundations of classical genetics, a fact recognised by the award of a Nobel Prize to Morgan in 1933 and to his student H.J. Muller in 1946, the latter being for Muller's discovery in 1928 that X-rays can cause mutations.
Today, there are about 7,500 researchers devoted to the study of fundamental problems in biology working with Drosophila. Many advances in our understanding of human development and human disease have come from this work, a fact recognised by the award in 1995 of the Nobel Prize for Physiology or Medicine to three Drosophila workers, Ed Lewis, Eric Weischaus and Christiane Nüsslein-Volhard.