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Drosophila melanogaster is a species of fly (the taxonomic order Diptera) in the family Drosophilidae. The species is often referred to as the fruit fly or lesser fruit fly, or less commonly the "vinegar fly" or "pomace fly".[a][4] Starting with Charles W. Woodworth's 1901 proposal of the use of this species as a model organism,[5][6] D. melanogaster continues to be widely used for biological research in genetics, physiology, microbial pathogenesis, and life history evolution. As of 2017, five Nobel Prizes have been awarded to drosophilists for their work using the insect.[7][8]

Melanogaster is typically used in research owing to its rapid life cycle, relatively simple genetics with only four pairs of chromosomes, and large number of offspring per generation.[9] It was originally an African species, with all non-African lineages having a common origin.[10] Its geographic range includes all continents, including islands.[11] D. melanogaster is a common pest in homes, restaurants, and other places where food is served.[12]

Flies belonging to the family Tephritidae are also called "fruit flies". This can cause confusion, especially in the Mediterranean, Australia, and South Africa, where the Mediterranean fruit fly Ceratitis capitata is an economic pest.

Flies are yellow-brown, with brick-red eyes and transverse black rings across the abdomen. The brick-red color of the eyes of the wild type fly are due to two pigments:[13] xanthommatin, which is brown and is derived from tryptophan, and drosopterins, which are red and are derived from guanosine triphosphate.[13] They exhibit sexual dimorphism; females are about 2.5 mm (0.10 in) long; males are slightly smaller with darker backs. Males are easily distinguished from females based on colour differences, with a distinct black patch at the abdomen, less noticeable in recently emerged flies, and the sexcombs (a row of dark bristles on the tarsus of the first leg). Furthermore, males have a cluster of spiky hairs (claspers) surrounding the reproducing parts used to attach to the female during mating. Extensive images are found at FlyBase.[14] Drosophila melanogaster flies can sense air currents with the hairs on their backs. Their eyes are sensitive to slight differences in light intensity and will instinctively fly away when a shadow or other movement is detected.[15]

Under optimal growth conditions at 25 °C (77 °F), the D. melanogaster lifespan is about 50 days from egg to death.[16] The developmental period for D. melanogaster varies with temperature, as with many ectothermic species. The shortest development time (egg to adult), 7 days, is achieved at 28 °C (82 °F).[17][18] Development times increase at higher temperatures (11 days at 30 °C or 86 °F) due to heat stress. Under ideal conditions, the development time at 25 °C (77 °F) is 8.5 days,[17][18][19] at 18 °C (64 °F) it takes 19 days[17][18] and at 12 °C (54 °F) it takes over 50 days.[17][18] Under crowded conditions, development time increases,[20] while the emerging flies are smaller.[20][21] Females lay some 400 eggs (embryos), about five at a time, into rotting fruit or other suitable material such as decaying mushrooms and sap fluxes. Drosophila melanogaster is a holometabolous insect, so it undergoes a full metamorphosis. Their life cycle is broken down into 4 stages: embryo, larva, pupa, adult.[22] The eggs, which are about 0.5 mm long, hatch after 12–15 hours (at 25 °C or 77 °F).[17][18] The resulting larvae grow for about 4 days (at 25 °C) while molting twice (into second- and third-instar larvae), at about 24 and 48 h after hatching.[17][18] During this time, they feed on the microorganisms that decompose the fruit, as well as on the sugar of the fruit itself. The mother puts feces on the egg sacs to establish the same microbial composition in the larvae's guts that has worked positively for herself.[23] Then the larvae encapsulate in the puparium and undergo a 4-day-long metamorphosis (at 25 °C), after which the adults eclose (emerge).[17][18]

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